diff --git a/caimira/setup.cfg b/caimira/setup.cfg
deleted file mode 100644
index 5d55bc97..00000000
--- a/caimira/setup.cfg
+++ /dev/null
@@ -1,2 +0,0 @@
-[tool:pytest]
-addopts = --mypy
diff --git a/caimira/src/caimira/calculator/models/models.py b/caimira/src/caimira/calculator/models/models.py
index 0cd151dd..774c3e93 100644
--- a/caimira/src/caimira/calculator/models/models.py
+++ b/caimira/src/caimira/calculator/models/models.py
@@ -799,7 +799,7 @@ class Activity:
 @dataclass(frozen=True)
 class SimplePopulation:
     """
-    Represents a group of people all with exactly the same behaviour and
+    Represents a group of people all with exactly the same behavior and
     situation.
 
     """
@@ -844,7 +844,7 @@ def people_present(self, time: float):
 @dataclass(frozen=True)
 class Population(SimplePopulation):
     """
-    Represents a group of people all with exactly the same behaviour and
+    Represents a group of people all with exactly the same behavior and
     situation, considering the usage of mask and a certain host immunity.
 
     """
@@ -1324,6 +1324,9 @@ class ShortRangeModel:
     #: Interpersonal distances
     distance: _VectorisedFloat
 
+    #: Expiration definition
+    expiration_def: typing.Optional[str] = None
+
     def dilution_factor(self) -> _VectorisedFloat:
         '''
         The dilution factor for the respective expiratory activity type.
@@ -1653,6 +1656,9 @@ def __post_init__(self):
         In other words, the air exchange rate from the
         ventilation, and the virus decay constant, must
         not be given as arrays.
+
+        It also checks that the number of exposed is
+        static during the simulation time.
         """
         c_model = self.concentration_model
         # Check if the diameter is vectorised.
@@ -1663,6 +1669,11 @@ def __post_init__(self):
                 c_model.ventilation.air_exchange(c_model.room, time)) for time in c_model.state_change_times()))):
             raise ValueError("If the diameter is an array, none of the ventilation parameters "
                              "or virus decay constant can be arrays at the same time.")
+        
+        # Check if exposed population is static
+        if not isinstance(self.exposed.number, int) or not isinstance(self.exposed.presence, Interval):
+            raise TypeError("The exposed number must be an int and presence an Interval. "
+                            f"Got {type(self.exposed.number)} and {type(self.exposed.presence)}.")
 
     @method_cache
     def population_state_change_times(self) -> typing.List[float]:
@@ -1809,11 +1820,9 @@ def _deposited_exposure_list(self):
         The number of virus per m^3 deposited on the respiratory tract.
         """
         population_change_times = self.population_state_change_times()
-
         deposited_exposure = []
         for start, stop in zip(population_change_times[:-1], population_change_times[1:]):
             deposited_exposure.append(self.deposited_exposure_between_bounds(start, stop))
-
         return deposited_exposure
 
     def deposited_exposure(self) -> _VectorisedFloat:
@@ -1838,8 +1847,7 @@ def infection_probability(self) -> _VectorisedFloat:
         return (1 - np.prod([1 - prob for prob in self._infection_probability_list()], axis = 0)) * 100
 
     def total_probability_rule(self) -> _VectorisedFloat:
-        if (isinstance(self.concentration_model.infected.number, IntPiecewiseConstant) or
-                isinstance(self.exposed.number, IntPiecewiseConstant)):
+        if (isinstance(self.concentration_model.infected.number, IntPiecewiseConstant)):
                 raise NotImplementedError("Cannot compute total probability "
                         "(including incidence rate) with dynamic occupancy")
 
@@ -1847,9 +1855,9 @@ def total_probability_rule(self) -> _VectorisedFloat:
             sum_probability = 0.0
 
             # Create an equivalent exposure model but changing the number of infected cases.
-            total_people = self.concentration_model.infected.number + self.exposed.number
+            total_people = self.concentration_model.infected.number + self.exposed.number # type: ignore
             max_num_infected = (total_people if total_people < 10 else 10)
-            # The influence of a higher number of simultainious infected people (> 4 - 5) yields an almost negligible contirbution to the total probability.
+            # The influence of a higher number of simultaneous infected people (> 4 - 5) yields an almost negligible contribution to the total probability.
             # To be on the safe side, a hard coded limit with a safety margin of 2x was set.
             # Therefore we decided a hard limit of 10 infected people.
             for num_infected in range(1, max_num_infected + 1):
@@ -1872,43 +1880,88 @@ def expected_new_cases(self) -> _VectorisedFloat:
             1) Long-range exposure: take the infection_probability and multiply by the occupants exposed to long-range. 
             2) Short- and long-range exposure: take the infection_probability of long-range multiplied by the occupants exposed to long-range only, 
                plus the infection_probability of short- and long-range multiplied by the occupants exposed to short-range only.
-
-        Currently disabled when dynamic occupancy is defined for the exposed population.
         """
-
-        if (isinstance(self.concentration_model.infected.number, IntPiecewiseConstant) or
-            isinstance(self.exposed.number, IntPiecewiseConstant)):
-            raise NotImplementedError("Cannot compute expected new cases "
-                    "with dynamic occupancy")
-
+        number = self.exposed.number
         if self.short_range != ():
-            new_cases_long_range = nested_replace(self, {'short_range': [],}).infection_probability() * (self.exposed.number - self.exposed_to_short_range)
+            new_cases_long_range = nested_replace(self, {'short_range': [],}).infection_probability() * (number - self.exposed_to_short_range) # type: ignore
             return (new_cases_long_range + (self.infection_probability() * self.exposed_to_short_range)) / 100
 
-        return self.infection_probability() * self.exposed.number / 100
+        return self.infection_probability() * number / 100
 
     def reproduction_number(self) -> _VectorisedFloat:
         """
         The reproduction number can be thought of as the expected number of
         cases directly generated by one infected case in a population.
-
-        Currently disabled when dynamic occupancy is defined for both the infected and exposed population.
         """
-
-        if (isinstance(self.concentration_model.infected.number, IntPiecewiseConstant) or
-            isinstance(self.exposed.number, IntPiecewiseConstant)):
-            raise NotImplementedError("Cannot compute reproduction number "
-                    "with dynamic occupancy")
-
-        if self.concentration_model.infected.number == 1:
+        infected_population: InfectedPopulation = self.concentration_model.infected
+        if isinstance(infected_population.number, int) and infected_population.number == 1:
             return self.expected_new_cases()
 
         # Create an equivalent exposure model but with precisely
-        # one infected case.
+        # one infected case, respecting the presence interval.
         single_exposure_model = nested_replace(
             self, {
-                'concentration_model.infected.number': 1}
+                'concentration_model.infected.number': 1,
+                'concentration_model.infected.presence': infected_population.presence_interval(),
+            }
         )
-
         return single_exposure_model.expected_new_cases()
+    
+
+@dataclass(frozen=True)
+class ExposureModelGroup:
+    """
+    Represents a group of exposure models. This is to handle the case
+    when different groups of people come and go in the room at different
+    times. These groups are then handled fully independently, with
+    exposure dose and probability of infection defined for each of them.
+    """
+    data_registry: DataRegistry
+
+    #: The set of exposure models for each exposed population
+    exposure_models: typing.Tuple[ExposureModel, ...]
+
+    @method_cache
+    def _deposited_exposure_list(self) -> typing.List[_VectorisedFloat]:
+        """
+        List of doses absorbed by each member of the groups.
+        """
+        return [model.deposited_exposure() for model in self.exposure_models]
+    
+    @method_cache
+    def _infection_probability_list(self):
+        """
+        List of the probability of infection for each group.
+        """
+        return [model.infection_probability() for model in self.exposure_models] # type: ignore
+
+    def expected_new_cases(self) -> _VectorisedFloat:
+        """
+        Final expected number of new cases considering the
+        contribution of each individual probability of infection.
+        """
+        return np.sum([model.expected_new_cases() for model in self.exposure_models], axis=0) # type: ignore
+    
+    def reproduction_number(self) -> _VectorisedFloat:
+        """
+        Reproduction number considering the contribution
+        of each individual probability of infection and
+        a single infected occupant.
+        """
+        single_exposure_models = []
+        for model in self.exposure_models:
+            if model.concentration_model.infected.number != 1:
+                model = nested_replace(
+                    self, {
+                        'model.concentration_model.infected.number': 1
+                    }
+                )
+            single_exposure_models.append(model)
+
+        single_exposure_model_group = nested_replace(
+            self, {
+                'exposure_models': single_exposure_models,
+            }
+        )
+        return single_exposure_model_group.expected_new_cases()
     
\ No newline at end of file
diff --git a/caimira/src/caimira/calculator/report/virus_report_data.py b/caimira/src/caimira/calculator/report/virus_report_data.py
index 6c4d62e6..93053272 100644
--- a/caimira/src/caimira/calculator/report/virus_report_data.py
+++ b/caimira/src/caimira/calculator/report/virus_report_data.py
@@ -16,9 +16,19 @@ def model_start_end(model: models.ExposureModel):
                   model.concentration_model.infected.presence_interval().boundaries()[0][0])
     t_end = max(model.exposed.presence_interval().boundaries()[-1][1],
                 model.concentration_model.infected.presence_interval().boundaries()[-1][1])
+    
     return t_start, t_end
 
 
+def model_boundary_times(model: typing.Union[models.ExposureModel, models.ExposureModelGroup]):
+    if isinstance(model, models.ExposureModelGroup):
+        t_start = min((model_start_end(nth_model)[0] for nth_model in model.exposure_models))
+        t_end = max((model_start_end(nth_model)[1] for nth_model in model.exposure_models))
+        return t_start, t_end
+    else:
+        return model_start_end(model)
+
+
 def fill_big_gaps(array, gap_size):
     """
     Insert values into the given sorted list if there is a gap of more than ``gap_size``.
@@ -42,7 +52,7 @@ def fill_big_gaps(array, gap_size):
     return result
 
 
-def non_temp_transition_times(model: models.ExposureModel):
+def non_temp_transition_times(model: typing.Union[models.ExposureModel, models.ExposureModelGroup]):
     """
     Return the non-temperature (and PiecewiseConstant) based transition times.
 
@@ -60,7 +70,7 @@ def walk_model(model, name=""):
             else:
                 yield name, obj
 
-    t_start, t_end = model_start_end(model)
+    t_start, t_end = model_boundary_times(model)
 
     change_times = {t_start, t_end}
     for name, obj in walk_model(model, name="exposure"):
@@ -72,7 +82,8 @@ def walk_model(model, name=""):
     return sorted(time for time in change_times if (t_start <= time <= t_end))
 
 
-def interesting_times(model: models.ExposureModel, approx_n_pts: typing.Optional[int] = None) -> typing.List[float]:
+def interesting_times(model: typing.Union[models.ExposureModel, models.ExposureModelGroup], 
+                      approx_n_pts: typing.Optional[int] = None) -> typing.List[float]:
     """
     Pick approximately ``approx_n_pts`` time points which are interesting for the
     given model. If not provided by argument, ``approx_n_pts`` is set to be 15 times
@@ -94,113 +105,191 @@ def interesting_times(model: models.ExposureModel, approx_n_pts: typing.Optional
     return nice_times
 
 
-def concentrations_with_sr_breathing(form: VirusFormData, model: models.ExposureModel, times: typing.List[float], short_range_intervals: typing.List) -> typing.List[float]:
+def process_short_range_interactions(model: typing.Union[models.ExposureModel, models.ExposureModelGroup], 
+                                     times: typing.List[float]):
+    """
+    Process both ExposureModel and ExposureModelGroup for short-range 
+    expirations, intervals and concentrations. Returns a tuple containing 
+    lower concentrations, short-range expirations, and short-range intervals.
+    """
+    if isinstance(model, models.ExposureModelGroup):
+        model_list = model.exposure_models
+    elif isinstance(model, models.ExposureModel):
+        model_list = (model,)
+    else:
+        raise TypeError(f"Model should be either an instance of ExposureModel or ExposureModelGroup. Got '{type(model)}.'")
+    
+    # Collect short-range expirations and intervals
+    short_range_expirations, short_range_intervals = [], []
+    for nth_model in model_list:
+        for nth_sr_model in nth_model.short_range:
+            short_range_expirations.append(nth_sr_model.expiration_def)
+            short_range_intervals.append(nth_sr_model.presence.boundaries()[0])
+            
+    # Collect lower concentrations (including Breathing)
     lower_concentrations = []
     for time in times:
-        for index, (start, stop) in enumerate(short_range_intervals):
-            # For visualization issues, add short-range breathing activity to the initial long-range concentrations
-            if start <= time <= stop and form.short_range_interactions[index]['expiration'] == 'Breathing':
-                lower_concentrations.append(
-                    np.array(model.concentration(float(time))).mean())
+        breathing_found = False
+        for nth_model in model_list:
+            for nth_sr_model in nth_model.short_range:
+                start, stop = nth_sr_model.presence.boundaries()[0]
+
+                # Check if the expiration is "Breathing" and the if time is within boundaries
+                if nth_sr_model.expiration_def == 'Breathing' and (start <= time <= stop):
+                    lower_concentrations.append(np.sum([np.array(nth_model.concentration(float(time))).mean() for nth_model in model_list]))
+                    breathing_found = True
+                    break
+
+            if breathing_found:
                 break
-        lower_concentrations.append(
-            np.array(model.concentration_model.concentration(float(time))).mean())
-    return lower_concentrations
+        
+        lower_concentrations.append(np.sum([np.array(nth_model.concentration_model.concentration(float(time))).mean() for nth_model in model_list]))
 
+    return lower_concentrations, short_range_expirations, short_range_intervals
 
-def _calculate_deposited_exposure(model, time1, time2, fn_name=None):
-    return np.array(model.deposited_exposure_between_bounds(float(time1), float(time2))).mean(), fn_name
 
+def _calculate_deposited_exposure(model: typing.Union[models.ExposureModel, models.ExposureModelGroup], 
+                                  time1: float, time2: float, fn_name: typing.Optional[str] = None):
+    if isinstance(model, models.ExposureModelGroup):
+        return np.sum([np.array(nth_model.deposited_exposure_between_bounds(float(time1), float(time2))).mean() for nth_model in model.exposure_models]), fn_name
+    else:
+        return np.array(model.deposited_exposure_between_bounds(float(time1), float(time2))).mean(), fn_name
 
-def _calculate_long_range_deposited_exposure(model, time1, time2, fn_name=None):
-    return np.array(model.long_range_deposited_exposure_between_bounds(float(time1), float(time2))).mean(), fn_name
+def _calculate_long_range_deposited_exposure(model: typing.Union[models.ExposureModel, models.ExposureModelGroup], 
+                                             time1: float, time2: float, fn_name: typing.Optional[str] = None):
+    if isinstance(model, models.ExposureModelGroup):
+        return np.sum([np.array(nth_model.long_range_deposited_exposure_between_bounds(float(time1), float(time2))).mean() for nth_model in model.exposure_models]), fn_name
+    else:
+        return np.array(model.long_range_deposited_exposure_between_bounds(float(time1), float(time2))).mean(), fn_name
 
+def _calculate_concentration(model: typing.Union[models.ExposureModel, models.ExposureModelGroup], 
+                             time: float, fn_name: typing.Optional[str] = None):
+    if isinstance(model, models.ExposureModelGroup):
+        return np.sum([np.array(nth_model.concentration(float(time))).mean() for nth_model in model.exposure_models]), fn_name
+    else:
+        return np.array(model.concentration(float(time))).mean(), fn_name
 
-def _calculate_co2_concentration(CO2_model, time, fn_name=None):
+def _calculate_co2_concentration(CO2_model: models.CO2ConcentrationModel, time: float, fn_name: typing.Optional[str] = None):
     return np.array(CO2_model.concentration(float(time))).mean(), fn_name
 
 
 @profiler.profile
 def calculate_report_data(form: VirusFormData, executor_factory: typing.Callable[[], concurrent.futures.Executor]) -> typing.Dict[str, typing.Any]:
-    model: models.ExposureModel = form.build_model()
-    
+    """
+    General output data of a test scenario.
+    """
+    model: typing.Union[models.ExposureModel, models.ExposureModelGroup] = form.build_model()
     times = interesting_times(model)
-    short_range_intervals = [interaction.presence.boundaries()[0]
-                             for interaction in model.short_range]
-    short_range_expirations = [interaction['expiration']
-                               for interaction in form.short_range_interactions] if form.short_range_option == "short_range_yes" else []
-
-    concentrations = [
-        np.array(model.concentration(float(time))).mean()
-        for time in times
-    ]
-    lower_concentrations = concentrations_with_sr_breathing(
-        form, model, times, short_range_intervals)
+    
+    if isinstance(model, models.ExposureModelGroup):
+        exposed_presence_intervals = []
+        probabilities_of_infection = []
+        for nth_model in model.exposure_models:
+            exposed_presence_intervals.extend(list(nth_model.exposed.presence_interval().boundaries()))
+            probabilities_of_infection.append(nth_model.infection_probability())
+            index_of_max_mean = max(
+                range(len(probabilities_of_infection)), 
+                key=lambda i: probabilities_of_infection[i].mean()
+            )
+            probability_of_infection = probabilities_of_infection[index_of_max_mean]
+    elif isinstance(model, models.ExposureModel):
+        exposed_presence_intervals = [list(interval) for interval in model.exposed.presence_interval().boundaries()]
+        probability_of_infection = model.infection_probability()
+    else:
+        raise TypeError(f"Model should be either an instance of ExposureModel or ExposureModelGroup. Got '{type(model)}.'")
+    
+    # Handle short-range related outputs
+    lower_concentrations, short_range_expirations, short_range_intervals = None, None, None
+     # Short-range related data:
+    if (form.short_range_option == "short_range_yes"):
+       lower_concentrations, short_range_expirations, short_range_intervals = process_short_range_interactions(model, times)
+    
+    # Probability of infection
+    prob = probability_of_infection
+    prob_dist_count, prob_dist_bins = np.histogram(prob/100, bins=100, density=True)
+
+    # Expected new cases
+    expected_new_cases = np.array(model.expected_new_cases()).mean()
 
+    # Expected number of new cases per group
+    # expected_new_cases_per_group = [np.array(model.expected_new_cases()).mean() for model in models_set.exposure_models]
+    
+    # CO2 concentration 
     CO2_model: models.CO2ConcentrationModel = form.build_CO2_model()
 
-    # compute deposited exposures and CO2 concentrations in parallel to increase performance
+    # Compute deposited exposures and virus/CO2 concentrations in parallel to increase performance
     deposited_exposures = []
     long_range_deposited_exposures = []
     CO2_concentrations = []
+    concentrations = []
 
     tasks = []
-    with executor_factory() as executor:
+    with executor_factory() as executor: # TODO: parallelism in the models
         for time1, time2 in zip(times[:-1], times[1:]):
             tasks.append(executor.submit(
                 _calculate_deposited_exposure, model, time1, time2, fn_name="de"))
             tasks.append(executor.submit(
-                _calculate_long_range_deposited_exposure, model, time1, time2, fn_name="lr"))
-            # co2 concentration: takes each time as param, not the interval
+                _calculate_long_range_deposited_exposure, model, time1, time2, fn_name="de_lr"))
+            tasks.append(executor.submit(
+                _calculate_concentration, model, time1, fn_name="cn"))
+            # virus and co2 concentration: takes each time as param, not the interval
             tasks.append(executor.submit(
                 _calculate_co2_concentration, CO2_model, time1, fn_name="co2"))
-        # co2 concentration: calculate the last time too
+        # virus and co2 concentration: calculate the last time too
+        tasks.append(executor.submit( _calculate_concentration, 
+                    model, times[-1], fn_name="cn"))
         tasks.append(executor.submit(_calculate_co2_concentration,
-                     CO2_model, times[-1], fn_name="co2"))
-
+                    CO2_model, times[-1], fn_name="co2"))
+    
     for task in tasks:
         result, fn_name = task.result()
         if fn_name == "de":
             deposited_exposures.append(result)
-        elif fn_name == "lr":
+        elif fn_name == "de_lr":
             long_range_deposited_exposures.append(result)
+        elif fn_name == "cn":
+            concentrations.append(result)
         elif fn_name == "co2":
             CO2_concentrations.append(result)
 
     cumulative_doses = np.cumsum(deposited_exposures)
     long_range_cumulative_doses = np.cumsum(long_range_deposited_exposures)
 
-    prob = np.array(model.infection_probability())
-    prob_dist_count, prob_dist_bins = np.histogram(prob/100, bins=100, density=True)
-    
-    # Probabilistic exposure and expected new cases (only for static occupancy)
     prob_probabilistic_exposure = None
-    expected_new_cases = None
-    if form.occupancy_format == "static":
-        if form.exposure_option == "p_probabilistic_exposure":
-            prob_probabilistic_exposure = np.array(model.total_probability_rule()).mean()
-        expected_new_cases =  np.array(model.expected_new_cases()).mean()
-
-    exposed_presence_intervals = [list(interval) for interval in model.exposed.presence_interval().boundaries()]
+    if isinstance(model, models.ExposureModel) and form.exposure_option == "p_probabilistic_exposure":
+        prob_probabilistic_exposure = np.array(model.total_probability_rule()).mean()
 
     conditional_probability_data = None
     uncertainties_plot_src = None
-    if (form.conditional_probability_viral_loads and
-            model.data_registry.virological_data['virus_distributions'][form.virus_type]['viral_load_in_sputum'] == ViralLoads.COVID_OVERALL.value):  # type: ignore
-        # Generate all the required data for the conditional probability plot
-        conditional_probability_data = manufacture_conditional_probability_data(
-            model, prob)
-        # Generate the matplotlib image based on the received data
-        uncertainties_plot_src = img2base64(_figure2bytes(
-            uncertainties_plot(prob, conditional_probability_data)))
+    if form.conditional_probability_viral_loads:
+        if isinstance(model, models.ExposureModelGroup):
+            all_the_same_virus = True
+            for nth_model in model.exposure_models:
+                if nth_model.data_registry.virological_data['virus_distributions'][form.virus_type]['viral_load_in_sputum'] != ViralLoads.COVID_OVERALL.value:  # type: ignore
+                    all_the_same_virus = False
+            if all_the_same_virus:
+                # Given the similarities, pick the first exposure model
+                the_model: models.ExposureModel = model.exposure_models[0]
+                # Generate all the required data for the conditional probability plot
+                conditional_probability_data = manufacture_conditional_probability_data(the_model, prob)
+                # Generate the matplotlib image based on the received data
+                uncertainties_plot_src = img2base64(_figure2bytes(uncertainties_plot(prob, conditional_probability_data)))
+        elif isinstance(model, models.ExposureModel):
+            if model.data_registry.virological_data['virus_distributions'][form.virus_type]['viral_load_in_sputum'] != ViralLoads.COVID_OVERALL.value:  # type: ignore
+                # Generate all the required data for the conditional probability plot
+                conditional_probability_data = manufacture_conditional_probability_data(model, prob)
+                # Generate the matplotlib image based on the received data
+                uncertainties_plot_src = img2base64(_figure2bytes(uncertainties_plot(prob, conditional_probability_data)))
+        else:
+            raise TypeError(f"Model should be either an instance of ExposureModel or ExposureModelGroup. Got '{type(model)}.'")
 
     return {
-        "model": model,
+        "model": model.exposure_models[0] if isinstance(model, models.ExposureModelGroup) else model, # TODO: which model do we want to show info about?
         "times": list(times),
         "exposed_presence_intervals": exposed_presence_intervals,
         "short_range_intervals": short_range_intervals,
         "short_range_expirations": short_range_expirations,
-        "concentrations": concentrations,
+        "concentrations": list(concentrations),
         "concentrations_zoomed": lower_concentrations,
         "cumulative_doses": list(cumulative_doses),
         "long_range_cumulative_doses": list(long_range_cumulative_doses),
@@ -349,7 +438,7 @@ def calculate_vl_scenarios_percentiles(model: mc.ExposureModel) -> typing.Dict[s
     }
 
 
-def manufacture_alternative_scenarios(form: VirusFormData) -> typing.Dict[str, mc.ExposureModel]:
+def manufacture_alternative_scenarios(form: VirusFormData) -> typing.Dict[str, mc.ExposureModelGroup]:
     scenarios = {}
     if (form.short_range_option == "short_range_no"):
         # Two special option cases - HEPA and/or FFP2 masks.
@@ -401,45 +490,61 @@ def manufacture_alternative_scenarios(form: VirusFormData) -> typing.Dict[str, m
             scenarios['No ventilation with Type I masks'] = with_mask_no_vent.build_mc_model()
         if not (form.mask_wearing_option == 'mask_off' and form.ventilation_type == 'no_ventilation'):
             scenarios['Neither ventilation nor masks'] = without_mask_or_vent.build_mc_model()
-
     else:
-        # When dynamic occupancy is defined, the replace of total people is useless - the expected number of new cases is not calculated.
+        # Adjust the number of exposed people with long-range exposure based on short-range interactions
         if form.occupancy_format == 'static':
-            no_short_range_alternative = dataclass_utils.replace(form, short_range_interactions=[], total_people=form.total_people - form.short_range_occupants)
+            no_short_range_alternative = dataclass_utils.replace(form, short_range_interactions={}, total_people=form.total_people - form.short_range_occupants)
         elif form.occupancy_format == 'dynamic':
-            for occ in form.dynamic_exposed_occupancy: # Update the number of exposed people with long-range exposure
-                if occ['total_people'] > form.short_range_occupants: occ['total_people'] = max(0, occ['total_people'] - form.short_range_occupants)
-            no_short_range_alternative = dataclass_utils.replace(form, short_range_interactions=[], dynamic_exposed_occupancy=form.dynamic_exposed_occupancy)
-        
+            for group_name, occupancy_list in form.dynamic_exposed_occupancy.items():
+                # Check if the group exists in short-range interactions
+                if group_name in form.short_range_interactions:
+                    short_range_count = form.short_range_occupants
+                    for occupancy in occupancy_list:
+                        total_people = occupancy.get('total_people', 0)
+                        if total_people > short_range_count > 0:
+                            # Update the total_people with the adjusted value
+                            occupancy['total_people'] = max(0, total_people - short_range_count)
+            no_short_range_alternative = dataclass_utils.replace(form, short_range_interactions={}, dynamic_exposed_occupancy=form.dynamic_exposed_occupancy)        
         scenarios['Base scenario without short-range interactions'] = no_short_range_alternative.build_mc_model()
 
     return scenarios
 
 
 def scenario_statistics(
-    mc_model: mc.ExposureModel,
+    mc_model: mc.ExposureModelGroup,
     sample_times: typing.List[float],
-    static_occupancy: bool,
     compute_prob_exposure: bool,
 ):
-    model = mc_model.build_model(
+    model: typing.Union[models.ExposureModel, models.ExposureModelGroup] = mc_model.build_model(
         size=mc_model.data_registry.monte_carlo['sample_size'])
-
-    return {
-        'probability_of_infection': np.mean(model.infection_probability()),
-        'expected_new_cases': np.mean(model.expected_new_cases()) if static_occupancy else None,
-        'concentrations': [
+    
+    if isinstance(model, models.ExposureModelGroup):
+        concentrations = [
+            np.sum([np.array(nth_model.concentration(float(time))).mean() for nth_model in model.exposure_models])
+            for time in sample_times
+        ]
+        prob = np.max([np.mean(nth_model.infection_probability()) for nth_model in model.exposure_models])
+    elif isinstance(model, models.ExposureModel):
+        concentrations = [
             np.mean(model.concentration(time))
             for time in sample_times
-        ],
-        'prob_probabilistic_exposure': model.total_probability_rule() if compute_prob_exposure else None,
+        ]
+        prob = np.mean(model.infection_probability())
+    else:
+        raise TypeError(f"Model should be either an instance of ExposureModel or ExposureModelGroup. Got '{type(model)}.'")
+
+    return {
+        'probability_of_infection': prob,
+        'expected_new_cases': np.mean(model.expected_new_cases()),
+        'concentrations': concentrations,
+        'prob_probabilistic_exposure': model.total_probability_rule() if isinstance(model, models.ExposureModel) and compute_prob_exposure else None
     }
 
 
 def comparison_report(
         form: VirusFormData,
         report_data: typing.Dict[str, typing.Any],
-        scenarios: typing.Dict[str, mc.ExposureModel],
+        scenarios: typing.Dict[str, mc.ExposureModelGroup],
         executor_factory: typing.Callable[[], concurrent.futures.Executor],
 ):
     if (form.short_range_option == "short_range_no"):
@@ -461,7 +566,6 @@ def comparison_report(
             scenario_statistics,
             scenarios.values(),
             [report_data['times']] * len(scenarios),
-            [static_occupancy] * len(scenarios),
             [compute_prob_exposure] * len(scenarios),
             timeout=60,
         )
diff --git a/caimira/src/caimira/calculator/validators/co2/co2_validator.py b/caimira/src/caimira/calculator/validators/co2/co2_validator.py
index 43ea6b7a..5b2b0023 100644
--- a/caimira/src/caimira/calculator/validators/co2/co2_validator.py
+++ b/caimira/src/caimira/calculator/validators/co2/co2_validator.py
@@ -50,7 +50,7 @@ class CO2FormData(FormData):
         'room_volume': NO_DEFAULT,
         'specific_breaks': '{}',
         'total_people': NO_DEFAULT,
-        'dynamic_exposed_occupancy': '[]',
+        'dynamic_exposed_occupancy': '{}',
         'occupancy_format': 'static',
     }
 
@@ -74,7 +74,7 @@ def validate(self):
                 raise TypeError(f'The room capacity should be a valid integer (> 0). Got {self.room_capacity}.')
 
         # Validate specific inputs - breaks (exposed and infected)
-        if self.specific_breaks != {}:
+        if self.specific_breaks != {} and self.occupancy_format == 'static':
             if type(self.specific_breaks) is not dict:
                 raise TypeError('The specific breaks should be in a dictionary.')
 
@@ -188,11 +188,6 @@ def generate_ventilation_plot(self,
 
             return img2base64(_figure2bytes(fig)), vent_plot_data
 
-    def population_present_changes(self, infected_presence: models.Interval, exposed_presence: models.Interval) -> typing.List[float]:
-        state_change_times = set(infected_presence.transition_times())
-        state_change_times.update(exposed_presence.transition_times())
-        return sorted(state_change_times)
-
     def ventilation_transition_times(self) -> typing.Tuple[float]:
         '''
         Check if the last time from the input data is
@@ -207,45 +202,16 @@ def ventilation_transition_times(self) -> typing.Tuple[float]:
         return tuple(vent_states)
 
     def build_model(self, sample_size = None) -> models.CO2DataModel:
-        # Build a simple infected and exposed population for the case when presence
-        # intervals and number of people are dynamic. Activity type is not needed.
-        if self.occupancy_format == 'dynamic':
-            if isinstance(self.dynamic_infected_occupancy, typing.List) and len(self.dynamic_infected_occupancy) > 0:
-                infected_people = self.generate_dynamic_occupancy(self.dynamic_infected_occupancy)
-                infected_presence = None
-            else:
-                raise TypeError(f'If dynamic occupancy is selected, a populated list of occupancy intervals is expected. Got "{self.dynamic_infected_occupancy}".')
-            if isinstance(self.dynamic_exposed_occupancy, typing.List) and len(self.dynamic_exposed_occupancy) > 0:
-                exposed_people = self.generate_dynamic_occupancy(self.dynamic_exposed_occupancy)
-                exposed_presence = None
-            else:
-                raise TypeError(f'If dynamic occupancy is selected, a populated list of occupancy intervals is expected. Got "{self.dynamic_exposed_occupancy}".')
-        else:
-            infected_people = self.infected_people
-            exposed_people = self.total_people - self.infected_people
-            infected_presence = self.infected_present_interval()
-            exposed_presence = self.exposed_present_interval()
-
-        infected_population = models.SimplePopulation(
-            number=infected_people,
-            presence=infected_presence,
-            activity=None, # type: ignore
-        )
-        exposed_population=models.SimplePopulation(
-            number=exposed_people,
-            presence=exposed_presence,
-            activity=None, # type: ignore
-        )
-        
-        all_state_changes=self.population_present_changes(infected_population.presence_interval(), 
-                                                          exposed_population.presence_interval())
-        total_people = [infected_population.people_present(stop) + exposed_population.people_present(stop)
-                        for _, stop in zip(all_state_changes[:-1], all_state_changes[1:])]
+        """
+        Builds a CO2 data model that considers data
+        from the defined population groups.
+        """
+        occupancy = self.build_CO2_piecewise()
 
         return models.CO2DataModel(
                 data_registry=self.data_registry,
                 room=models.Room(volume=self.room_volume, capacity=self.room_capacity),
-                occupancy=models.IntPiecewiseConstant(transition_times=tuple(all_state_changes), values=tuple(total_people)),
+                occupancy=occupancy,
                 ventilation_transition_times=self.ventilation_transition_times(),
                 times=self.CO2_data['times'],
                 CO2_concentrations=self.CO2_data['CO2'],
diff --git a/caimira/src/caimira/calculator/validators/defaults.py b/caimira/src/caimira/calculator/validators/defaults.py
index bd14db38..00205281 100644
--- a/caimira/src/caimira/calculator/validators/defaults.py
+++ b/caimira/src/caimira/calculator/validators/defaults.py
@@ -82,7 +82,8 @@
 
 # ------------------ Validation ----------------------
 COFFEE_OPTIONS_INT = {'coffee_break_0': 0, 'coffee_break_1': 1,
-                      'coffee_break_2': 2, 'coffee_break_4': 4}
+                      'coffee_break_2': 2, 'coffee_break_3': 3, 
+                      'coffee_break_4': 4}
 CONFIDENCE_LEVEL_OPTIONS = {'confidence_low': 10,
                             'confidence_medium': 5, 'confidence_high': 2}
 MECHANICAL_VENTILATION_TYPES = {
diff --git a/caimira/src/caimira/calculator/validators/form_validator.py b/caimira/src/caimira/calculator/validators/form_validator.py
index fe2e58dc..0b6782ef 100644
--- a/caimira/src/caimira/calculator/validators/form_validator.py
+++ b/caimira/src/caimira/calculator/validators/form_validator.py
@@ -6,6 +6,7 @@
 import json
 import re
 
+from collections import defaultdict
 import numpy as np
 
 from .defaults import DEFAULTS, NO_DEFAULT, COFFEE_OPTIONS_INT
@@ -42,7 +43,7 @@ class FormData:
     total_people: int
 
     # Dynamic occupancy inputs
-    dynamic_exposed_occupancy: list
+    dynamic_exposed_occupancy: dict
     dynamic_infected_occupancy: list
 
     data_registry: DataRegistry
@@ -96,8 +97,196 @@ def to_dict(cls, form: "FormData", strip_defaults: bool = False) -> dict:
                 if default is not NO_DEFAULT and value in [default, 'not-applicable']:
                     form_dict.pop(attr)
         return form_dict
+    
+    def validate_dynamic_input(self, dynamic_input_value, input_name, dynamic_input_key = None):
+        # Check if dynamic_input is a list
+        if not isinstance(dynamic_input_value, list) and len(dynamic_input_value) > 0:
+            raise TypeError(f'The input "{input_name}" should be a list. Got "{type(dynamic_input_value)}".')
+        
+        # To store already processed interactions for overlap checking
+        existing_dynamic_infected_interval = []
+        existing_dynamic_exposed_interval = []
+        short_range_existing_interaction = []
+        
+        for entry in dynamic_input_value:
+            # Check if each entry is a dictionary
+            if not isinstance(entry, typing.Dict):
+                raise TypeError(f'Each entry in "{input_name}" should be a dictionary. Got "{type(entry)}".')
+
+            # Check for required keys in each entry
+            dict_keys = entry.keys()
+
+            # Check for the "total_people" key for "dynamic_exposed_occupancy" and "dynamic_infected_occupancy"
+            if input_name in ["dynamic_exposed_occupancy", "dynamic_infected_occupancy"]:
+                # Check for time format in "start_time" and "finish_time"
+                for time_key in ["start_time", "finish_time"]:
+                    if time_key not in dict_keys:
+                        raise TypeError(f'Missing "{time_key}" key in "{input_name}". Got keys: "{list(dict_keys)}".')
+                    time_value = entry[time_key]
+                    if not re.compile("^(2[0-3]|[01]?[0-9]):([0-5]?[0-9])$").match(time_value):
+                        raise ValueError(f'Invalid time format for "{time_key}" in "{input_name}". Expected "HH:MM". Got "{time_value}".')
+                    
+                # Check for the "total_people" key and its constraints
+                if "total_people" not in dict_keys:
+                    raise TypeError(f'Missing "total_people" key in "{input_name}". Got keys: "{list(dict_keys)}".')
+                else:
+                    value = entry["total_people"]
+                    if not isinstance(value, int) or value < 0:
+                        raise ValueError(f'The "total_people" in "{input_name}" should be a non-negative integer. Got "{value}".')
+                    
+            # Check for the "dynamic_infected_occupancy" uniqueness of intervals
+            if input_name == "dynamic_infected_occupancy":
+                self.check_overlap(entry, existing_dynamic_infected_interval)
+                existing_dynamic_infected_interval.append(entry)
+            
+            # Check for the "dynamic_exposed_occupancy" uniqueness of intervals
+            if input_name == "dynamic_exposed_occupancy":
+                self.check_overlap(entry, existing_dynamic_exposed_interval)
+                existing_dynamic_exposed_interval.append(entry)
+
+            # Check for remaining short-range inputs
+            if input_name == "short_range_interactions":
+                # Check for time format in "start_time" and "finish_time"
+                if "start_time" not in dict_keys:
+                    raise TypeError(f'Missing "start_time" key in "short_range_interactions". Got keys: "{list(dict_keys)}".')
+                start_time = entry["start_time"]
+                if not re.compile("^(2[0-3]|[01]?[0-9]):([0-5]?[0-9])$").match(start_time):
+                    raise ValueError(f'Invalid time format for "start_time" in "short_range_interactions". Expected "HH:MM". Got "{start_time}".')
+                
+                # Check for the "expiration" key and its constraints
+                if "expiration" not in dict_keys:
+                    raise TypeError(f'Missing "expiration" key in "short_range_interactions". Got keys: "{list(dict_keys)}".')
+                else:
+                    value = entry["expiration"]
+                    if value not in list(self.data_registry.expiration_particle['expiration_BLO_factors'].keys()):
+                        raise ValueError(f'The "expiration" in "short_range_interactions" does not exist in the registry. Got "{value}".')
+                
+                if "duration" not in dict_keys:
+                    raise TypeError(f'Missing "duration" key in "short_range_interactions". Got keys: "{list(dict_keys)}".')
+                duration = entry["duration"]
+                if duration < 0:
+                    raise ValueError(f'The "duration" in "short_range_interactions" should be a non-negative integer. Got "{duration}".')
+                
+                # Occupancy format dependent inputs
+                if self.occupancy_format == 'dynamic':
+                    # Find corresponding exposure group
+                    exposure_group_obj = next(
+                        (occupancy_value for occupancy_key, occupancy_value in self.dynamic_exposed_occupancy.items()
+                        if occupancy_key == dynamic_input_key),
+                        None
+                    )
+
+                    if exposure_group_obj is None:
+                        raise ValueError(
+                            f'Exposure group "{dynamic_input_key}" in short-range interaction not found in dynamic exposed occupancy.'
+                        )
+
+                    has_exposed_people = False
+                    is_within_any_long_range = False
+                    for exposure_interval in exposure_group_obj:
+                        if exposure_interval['total_people'] > 0:
+                            # Flag to check the presence of exposed people
+                            has_exposed_people = True
+
+                            # Check for correct timing within long-range exposure and overlaps with existing interactions
+                            long_range_start = time_string_to_minutes(exposure_interval['start_time'])/60
+                            long_range_stop = time_string_to_minutes(exposure_interval['finish_time'])/60
+                            
+                            # Flag to check if interaction falls within any long-range exposure interval
+                            if self.check_time_and_overlap(
+                                entry, short_range_existing_interaction, long_range_start, long_range_stop
+                            ): is_within_any_long_range = True
+                            
+                            # Add interaction to the list of processed interactions if within long-range
+                            short_range_existing_interaction.append(entry)
+
+                    # Check if no interval had people exposed
+                    if not has_exposed_people:
+                        raise ValueError("No intervals with exposed people were found in the exposure group.")
+                    
+                    # If no long-range interval contains the interaction, raise an error
+                    if not is_within_any_long_range:
+                        raise ValueError(
+                            f'Short-range interaction "{entry}" does not fall within any long-range exposure interval.'
+                        )
+                    
+                elif self.occupancy_format == 'static':
+                    # It means that we have a single exposure model
+                    long_range_start = min(self.infected_start, self.exposed_start)/60
+                    long_range_stop = max(self.infected_finish, self.exposed_finish)/60
+                    
+                    if not self.check_time_and_overlap(entry, short_range_existing_interaction, long_range_start, long_range_stop):
+                        raise ValueError(
+                            f'Short-range interactions should be defined during simulation time. Got "{entry}".'
+                        )
+                    
+                    # Add interaction to the list of processed interactions
+                    short_range_existing_interaction.append(entry)
+                else:
+                    raise TypeError(
+                        f'Undefined exposure type. Got "{self.occupancy_format}", accepted formats are "dynamic" or "exposed".')
+    
+    def validate_dynamic_exposed_number(self, dynamic_exposed_value):
+        """
+        It validates that the number of exposed people per group is the
+        same during the simulation time, except when breaks are defined 
+        (0 people is an allowed value).
+        """
+        occupancy_values = {entry["total_people"] for entry in dynamic_exposed_value if entry["total_people"] != 0}
+        if len(occupancy_values) > 1: # unique values collected in the set
+            raise ValueError(f"Inconsistent 'total_people' values found: {occupancy_values}. Within a group, the values should be identical.")
+
+    def get_start_and_finish_time(self, entry: dict):
+        entry_start = time_string_to_minutes(entry["start_time"])/60
+        if "finish_time" in list(entry.keys()):
+            entry_finish = time_string_to_minutes(entry["finish_time"])/60
+        else:
+            entry_finish = entry_start + entry['duration']/60
+        return entry_start, entry_finish
+
+    def check_time_and_overlap(self, interaction, existing_interactions, lr_start, lr_stop):
+        """
+        Checks if the interaction overlaps with any existing interactions for the
+        same exposure group and if it falls within the long-range exposure time.
+        """
+        interaction_start, interaction_finish = self.get_start_and_finish_time(interaction)
+        # Check if the SR interaction is within the LR exposure time
+        if lr_start <= interaction_start <= lr_stop and lr_start <= interaction_finish <= lr_stop:
+            for existing in existing_interactions:
+                existing_start, existing_finish = self.get_start_and_finish_time(existing)
+                # Check for overlap
+                if interaction_start < existing_finish and existing_start < interaction_finish:
+                    raise ValueError(
+                        f'Overlap detected for "short-range interaction": New interaction '
+                        f'"{interaction}" overlaps with existing interaction "{existing}".'
+                    )
+            # Return True if interaction falls within the current long-range interval
+            return True
+        return False
+    
+    def check_overlap(self, interaction, existing_interactions):
+        """
+        Checks if the dynamic infected entry overlaps with any existing interactions
+        for the same exposure group and if it falls within the long-range exposure time.
+        """
+        interaction_start = time_string_to_minutes(interaction["start_time"])/60
+        interaction_finish = time_string_to_minutes(interaction["finish_time"])/60
+        
+        for existing in existing_interactions:
+            existing_start = time_string_to_minutes(existing["start_time"])/60
+            existing_finish = time_string_to_minutes(existing["finish_time"])/60
 
+            # Check for overlap
+            if (interaction_start < existing_finish and existing_start < interaction_finish):
+                raise ValueError(
+                    f'Overlap detected: New interaction '
+                    f'"{interaction}" overlaps with existing interaction "{existing}".'
+            )
+        return
+    
+    
     def validate_population_parameters(self):
+        """Validates required parameters for dynamic inputs"""
         # Static occupancy is defined.
         if self.occupancy_format == 'static':        
             # Validate number of infected <= number of total people
@@ -172,34 +361,15 @@ def get_activity_mins(population):
                             f"{getattr(self, attr_name)} is not a valid value for {attr_name}")
         # Dynamic occupancy is defined.
         elif self.occupancy_format == 'dynamic':
-            for dynamic_format in (self.dynamic_infected_occupancy, self.dynamic_exposed_occupancy):
-                for occupancy in dynamic_format:
-                    # Check if each occupancy entry is a dictionary
-                    if not isinstance(occupancy, typing.Dict):
-                        raise TypeError(f'Each occupancy entry should be in a dictionary format. Got "{type(occupancy)}".')
-                    
-                    # Check for required keys in each occupancy entry
-                    dict_keys = list(occupancy.keys())
-                    if "total_people" not in dict_keys:
-                        raise TypeError(f'Unable to fetch "total_people" key. Got "{dict_keys}".')
-                    else:
-                        value = occupancy["total_people"]
-                        # Check if the value is a non-negative integer
-                        if not isinstance(value, int):
-                            raise ValueError(f'Total number of people should be integer. Got "{type(value)}".')
-                        elif not value >= 0:
-                            raise ValueError(f'Total number of people should be non-negative. Got "{value}".')
-                    
-                    if "start_time" not in dict_keys:
-                        raise TypeError(f'Unable to fetch "start_time" key. Got "{dict_keys}".')
-                    if "finish_time" not in dict_keys:
-                        raise TypeError(f'Unable to fetch "finish_time" key. Got "{dict_keys}".')
-
-                    # Validate time format for start_time and finish_time
-                    for time_key in ["start_time", "finish_time"]:
-                        time = occupancy[time_key]
-                        if not re.compile("^(2[0-3]|[01]?[0-9]):([0-5]?[0-9])$").match(time):
-                            raise TypeError(f'Wrong time format - "HH:MM". Got "{time}".')
+            # Validate dynamic input format
+            self.validate_dynamic_input(self.dynamic_infected_occupancy, "dynamic_infected_occupancy")
+            if isinstance(self.dynamic_exposed_occupancy, dict):
+                # The key is the actual identifier
+                for key, group in self.dynamic_exposed_occupancy.items():
+                    # Validate dynamic input format
+                    self.validate_dynamic_input(group, "dynamic_exposed_occupancy", key)
+                    # Validate number of people per exposure group
+                    self.validate_dynamic_exposed_number(group)
         else:
             raise ValueError(f"'{self.occupancy_format}' is not a valid value for 'self.occupancy_format'. Accepted values are 'static' or 'dynamic'.")
 
@@ -208,6 +378,70 @@ def validate(self):
 
     def build_model(self, sample_size: typing.Optional[int] = None):
         raise NotImplementedError("Subclass must implement")
+    
+    def population_present_changes(self, population_list: typing.List[models.Interval]) -> typing.List[float]:
+        """
+        Returns a sorted list of unique state changes on
+        a population list.
+        """
+        state_change_times = set(population_list[0].transition_times())
+        for population in population_list:
+            state_change_times.update(population.transition_times())
+        return sorted(state_change_times)
+
+    def build_CO2_piecewise(self):
+        """
+        Builds a simple IntPiecewiseConstant for the different
+        population groups that are defined.
+        """
+        if self.occupancy_format == 'dynamic':
+            infected_occupancy = self.generate_dynamic_occupancy(self.dynamic_infected_occupancy)
+            total_presence = [infected_occupancy.interval()]
+            total_models = [models.SimplePopulation(
+                number=infected_occupancy,
+                presence=None,
+                activity=None, # type: ignore
+            )]
+
+            for _, group in self.dynamic_exposed_occupancy.items():
+                group_occupancy = self.generate_dynamic_occupancy(group)
+                total_presence.append(group_occupancy.interval())
+                total_models.append(models.SimplePopulation(
+                    number=group_occupancy,
+                    presence=None,
+                    activity=None, # type: ignore
+                ))
+        
+        elif self.occupancy_format == 'static':
+            infected_people = self.infected_people
+            exposed_people = self.total_people - self.infected_people
+            infected_presence = self.infected_present_interval()
+            exposed_presence = self.exposed_present_interval()
+
+            infected_population = models.SimplePopulation(
+                number=infected_people,
+                presence=infected_presence,
+                activity=None, # type: ignore
+            )
+            exposed_population=models.SimplePopulation(
+                number=exposed_people,
+                presence=exposed_presence,
+                activity=None, # type: ignore
+            )
+            
+            total_presence = [infected_presence, exposed_presence]
+            total_models = [infected_population, exposed_population]
+
+        # Get all state change times from combined populations
+        all_state_changes=self.population_present_changes(total_presence)
+
+        # Compute total people at each state change
+        total_people = []
+        for _, stop in zip(all_state_changes[:-1], all_state_changes[1:]):
+            total_people_in_group = sum(population.people_present(stop) for population in total_models)
+            total_people.append(total_people_in_group)
+
+        return models.IntPiecewiseConstant(transition_times=tuple(all_state_changes), values=tuple(total_people))
 
     def _compute_breaks_in_interval(self, start, finish, n_breaks, duration) -> models.BoundarySequence_t:
         break_delay = ((finish - start) -
@@ -419,16 +653,39 @@ def exposed_present_interval(self) -> models.Interval:
         )
     
     def generate_dynamic_occupancy(self, dynamic_occupancy: typing.List[typing.Dict[str, typing.Any]]):
+        """
+        Generates a piecewise constant model for occupancy over time, accounting for any gaps 
+        between defined occupancy periods by inserting zero occupancy where no data is provided.
+        """
         transition_times = []
         values = []
-        for occupancy in dynamic_occupancy:
-            start_time = time_string_to_minutes(occupancy['start_time'])/60
-            finish_time = time_string_to_minutes(occupancy['finish_time'])/60
+
+        # Sort occupancy entries by start_time to ensure proper ordering
+        dynamic_occupancy_sorted = sorted(
+            dynamic_occupancy, key=lambda x: time_string_to_minutes(x['start_time'])
+        )
+
+        last_finish_time = None
+        for occupancy in dynamic_occupancy_sorted:
+            start_time = time_string_to_minutes(occupancy['start_time']) / 60
+            finish_time = time_string_to_minutes(occupancy['finish_time']) / 60
+            total_people = occupancy['total_people']
+
+            # Fill in gap with a zero occupancy if there is a time gap
+            if last_finish_time is not None and start_time > last_finish_time:
+                transition_times.append(last_finish_time)
+                values.append(0)  # Add zero for the gap period
+
+            # Update lists with current occupancy entry
             transition_times.extend([start_time, finish_time])
-            values.append(occupancy['total_people'])
+            values.append(total_people)
+
+            # Update the last known finish time
+            last_finish_time = finish_time
 
         unique_transition_times_sorted = np.array(sorted(set(transition_times)))
 
+        # Validate that we have enough values to compute the occupancy
         if len(values) != len(unique_transition_times_sorted) - 1:
             raise ValueError("Cannot compute dynamic occupancy with the provided inputs.")
         
@@ -450,6 +707,8 @@ def time_string_to_minutes(time: str) -> minutes_since_midnight:
     :param time: A string of the form "HH:MM" representing a time of day
     :return: The number of minutes between 'time' and 00:00
     """
+    if not (0 <= int(time[:2]) <= 23) or not (0 <= int(time[3:]) <= 59):
+        raise ValueError(f"Wrong time format. Got {time}")
     return minutes_since_midnight(60 * int(time[:2]) + int(time[3:]))
 
 
diff --git a/caimira/src/caimira/calculator/validators/virus/virus_validator.py b/caimira/src/caimira/calculator/validators/virus/virus_validator.py
index ca491b7f..60405c2b 100644
--- a/caimira/src/caimira/calculator/validators/virus/virus_validator.py
+++ b/caimira/src/caimira/calculator/validators/virus/virus_validator.py
@@ -4,6 +4,7 @@
 import typing
 import re
 
+from collections import defaultdict
 import numpy as np
 
 from caimira import __version__ as calculator_version
@@ -11,7 +12,7 @@
 from ..defaults import (DEFAULTS, CONFIDENCE_LEVEL_OPTIONS,
                         MECHANICAL_VENTILATION_TYPES, MASK_WEARING_OPTIONS, MONTH_NAMES, VACCINE_BOOSTER_TYPE, VACCINE_TYPE,
                         VENTILATION_TYPES, VOLUME_TYPES, WINDOWS_OPENING_REGIMES, WINDOWS_TYPES)
-from ...models import models, data, monte_carlo as mc
+from ...models import models, data, dataclass_utils, monte_carlo as mc
 from ...models.monte_carlo.data import activity_distributions, virus_distributions, mask_distributions, short_range_distances
 from ...models.monte_carlo.data import expiration_distribution, expiration_BLO_factors, expiration_distributions, short_range_expiration_distributions
 
@@ -67,13 +68,13 @@ class VirusFormData(FormData):
     window_opening_regime: str
     sensor_in_use: str
     short_range_option: str
-    short_range_interactions: list
+    short_range_interactions: dict
     short_range_occupants: int
 
     _DEFAULTS: typing.ClassVar[typing.Dict[str, typing.Any]] = DEFAULTS
 
     def validate(self):
-        # Validate population parameters 
+        # Validate population parameters
         self.validate_population_parameters()
 
         validation_tuples = [('activity_type', self.data_registry.population_scenario_activity.keys()),
@@ -203,30 +204,31 @@ def validate(self):
                     f'The sum of all respiratory activities should be 100. Got {total_percentage}.')
 
         # Validate number of people with short-range interactions
-        if self.occupancy_format == "static": max_occupants_for_sr = self.total_people - self.infected_people
-        else: max_occupants_for_sr = np.max(np.array([entry["total_people"] for entry in self.dynamic_exposed_occupancy]))
+        if self.occupancy_format == "static":
+            max_occupants_for_sr = self.total_people - self.infected_people
+        elif self.occupancy_format == 'dynamic':
+            max_occupants_for_sr = 0
+            for key, group in self.dynamic_exposed_occupancy.items():
+                max_occupants_group = np.max(
+                    np.array([entry["total_people"] for entry in group]))
+                if max_occupants_group > max_occupants_for_sr: max_occupants_for_sr = max_occupants_group
         if self.short_range_occupants > max_occupants_for_sr:
             raise ValueError(
                 f'The total number of occupants having short-range interactions ({self.short_range_occupants}) should be lower than the exposed population ({max_occupants_for_sr}).'
             )
-        
+
         # Validate short-range interactions interval
         if self.short_range_option == "short_range_yes":
-            for interaction in self.short_range_interactions:
-                # Check if presence is within long-range exposure
-                presence = self.short_range_interval(interaction)
-                if (self.occupancy_format == 'dynamic'):
-                    long_range_start = min(time_string_to_minutes(self.dynamic_infected_occupancy[0]['start_time']), 
-                                            time_string_to_minutes(self.dynamic_exposed_occupancy[0]['start_time']))
-                    long_range_stop = max(time_string_to_minutes(self.dynamic_infected_occupancy[-1]['finish_time']), 
-                                            time_string_to_minutes(self.dynamic_exposed_occupancy[-1]['finish_time']))
-                else:
-                    long_range_start = min(self.infected_start, self.exposed_start)
-                    long_range_stop = max(self.infected_finish, self.exposed_finish)
-                if not (long_range_start/60 <= presence.present_times[0][0] <= long_range_stop/60 and 
-                        long_range_start/60 <= presence.present_times[0][-1] <= long_range_stop/60):
-                    raise ValueError(f"Short-range interactions should be defined during simulation time. Got {interaction}")
-
+            if isinstance(self.short_range_interactions, dict):
+                # Check if occupancy format is static, there should be one key-value only in short_range_interactions
+                if self.occupancy_format == "static" and len(self.short_range_interactions) > 1:
+                    raise ValueError(
+                        'When occupancy format is "static", there should be only one interaction group in "short_range_interactions".'
+                    )
+                # The key is the actual identifier
+                for key, group in self.short_range_interactions.items():
+                    self.validate_dynamic_input(group, "short_range_interactions", key)
+    
     def initialize_room(self) -> models.Room:
         # Initializes room with volume either given directly or as product of area and height
         if self.volume_type == 'room_volume_explicit':
@@ -246,69 +248,100 @@ def initialize_room(self) -> models.Room:
 
         return models.Room(volume=volume, inside_temp=models.PiecewiseConstant((0, 24), (inside_temp,)), humidity=humidity) # type: ignore
 
-    def build_mc_model(self) -> mc.ExposureModel:
-        room = self.initialize_room()
+    def build_mc_model(self) -> typing.Union[mc.ExposureModel, mc.ExposureModelGroup]:
+        size = self.data_registry.monte_carlo['sample_size']
+
+        room: models.Room = self.initialize_room()
         ventilation: models._VentilationBase = self.ventilation()
         infected_population: models.InfectedPopulation = self.infected_population()
-        short_range = []
+
+        short_range = defaultdict(list)
         if self.short_range_option == "short_range_yes":
-            for interaction in self.short_range_interactions:
-                short_range.append(mc.ShortRangeModel(
-                    data_registry=self.data_registry,
-                    expiration=short_range_expiration_distributions(
-                        self.data_registry)[interaction['expiration']],
-                    activity=infected_population.activity,
-                    presence=self.short_range_interval(interaction),
-                    distance=short_range_distances(self.data_registry),
-                ))
-
-        return mc.ExposureModel(
+            for key, group in self.short_range_interactions.items():
+                for interaction in group:
+                    expiration = short_range_expiration_distributions(self.data_registry)[interaction['expiration']]
+                    presence = self.short_range_interval(interaction)
+                    distances = short_range_distances(self.data_registry)
+                    short_range[key].append(mc.ShortRangeModel(
+                        data_registry=self.data_registry,
+                        expiration=expiration,
+                        activity=infected_population.activity,
+                        presence=presence,
+                        distance=distances,
+                        expiration_def=interaction['expiration']
+                    ).build_model(size))
+
+        concentration_model: models.ConcentrationModel = mc.ConcentrationModel(
             data_registry=self.data_registry,
-            concentration_model=mc.ConcentrationModel(
+            room=room,
+            ventilation=ventilation,
+            infected=infected_population,
+            evaporation_factor=0.3,
+        ).build_model(size)
+
+        geographical_data: models.Cases = mc.Cases(
+            geographic_population=self.geographic_population,
+            geographic_cases=self.geographic_cases,
+            ascertainment_bias=CONFIDENCE_LEVEL_OPTIONS[self.ascertainment_bias],
+        ).build_model(size)
+
+        if self.occupancy_format == 'dynamic':
+            exposure_model_set = []
+            for exposure_group_key, exposed_group in self.dynamic_exposed_occupancy.items():
+                sr_models: typing.Tuple[models.ShortRangeModel, ...] = tuple(short_range[exposure_group_key])
+                population_occupancy = self.generate_dynamic_occupancy(exposed_group)
+                exposed_population: mc.Population = self.exposed_population(population_occupancy).build_model(size)
+
+                exposure_model = mc.ExposureModel(
+                    data_registry=self.data_registry,
+                    concentration_model=concentration_model,
+                    short_range=sr_models,
+                    exposed=exposed_population,
+                    geographical_data=geographical_data,
+                    exposed_to_short_range=self.short_range_occupants,
+                )
+                exposure_model_set.append(exposure_model)
+
+            if len(list(self.dynamic_exposed_occupancy.keys())) == 1:
+                return exposure_model_set[0]
+            else:
+                return mc.ExposureModelGroup(
+                    data_registry=self.data_registry,
+                    exposure_models=[individual_model.build_model(size) for individual_model in exposure_model_set]
+                )
+
+        elif self.occupancy_format == 'static':
+            exposed_population = self.exposed_population()
+            short_range_tuple = tuple(item for sublist in short_range.values() for item in sublist)
+            return mc.ExposureModel(
                 data_registry=self.data_registry,
-                room=room,
-                ventilation=ventilation,
-                infected=infected_population,
-                evaporation_factor=0.3,
-            ),
-            short_range=tuple(short_range),
-            exposed=self.exposed_population(),
-            geographical_data=mc.Cases(
-                geographic_population=self.geographic_population,
-                geographic_cases=self.geographic_cases,
-                ascertainment_bias=CONFIDENCE_LEVEL_OPTIONS[self.ascertainment_bias],
-            ),
-            exposed_to_short_range=self.short_range_occupants,
-        )
+                concentration_model=concentration_model,
+                short_range=short_range_tuple,
+                exposed=exposed_population,
+                geographical_data=geographical_data,
+                exposed_to_short_range=self.short_range_occupants,
+            )
 
-    def build_model(self, sample_size=None) -> models.ExposureModel:
-        sample_size = sample_size or self.data_registry.monte_carlo['sample_size']
-        return self.build_mc_model().build_model(size=sample_size)
+    def build_model(self, sample_size=None) -> typing.Union[models.ExposureModel, models.ExposureModelGroup]:
+        size = self.data_registry.monte_carlo['sample_size'] if not sample_size else sample_size
+        return self.build_mc_model().build_model(size=size)
 
     def build_CO2_model(self, sample_size=None) -> models.CO2ConcentrationModel:
+        """
+        Builds a CO2 model that considers the type of
+        activity and data from the defined population groups.
+        """
         sample_size = sample_size or self.data_registry.monte_carlo['sample_size']
-        infected_population: models.InfectedPopulation = self.infected_population(
-        ).build_model(sample_size)
-        exposed_population: models.Population = self.exposed_population().build_model(sample_size)
-
-        state_change_times = set(
-            infected_population.presence_interval().transition_times())
-        state_change_times.update(
-            exposed_population.presence_interval().transition_times())
-        transition_times = sorted(state_change_times)
-
-        total_people = [infected_population.people_present(stop) + exposed_population.people_present(stop)
-                        for _, stop in zip(transition_times[:-1], transition_times[1:])]
 
         if (self.activity_type == 'precise'):
             activity_defn, _ = self.generate_precise_activity_expiration()
         else:
             activity_defn = self.data_registry.population_scenario_activity[
                 self.activity_type]['activity']
-
+        
+        occupancy = self.build_CO2_piecewise()
         population = mc.SimplePopulation(
-            number=models.IntPiecewiseConstant(transition_times=tuple(
-                transition_times), values=tuple(total_people)),
+            number=occupancy,
             presence=None,
             activity=activity_distributions(self.data_registry)[activity_defn],
         )
@@ -423,6 +456,7 @@ def ventilation(self) -> models._VentilationBase:
         # This is a minimal, always present source of ventilation, due
         # to the air infiltration from the outside.
         # See CERN-OPEN-2021-004, p. 12.
+        # type: ignore
         residual_vent: float = self.data_registry.ventilation['infiltration_ventilation'] # type: ignore
         infiltration_ventilation = models.AirChange(
             active=always_on, air_exch=residual_vent)
@@ -465,13 +499,8 @@ def infected_population(self) -> mc.InfectedPopulation:
 
         # Occupancy
         if self.occupancy_format == 'dynamic':
-            if isinstance(self.dynamic_infected_occupancy, typing.List) and len(self.dynamic_infected_occupancy) > 0:
-                # If dynamic occupancy is defined, the generator will parse and validate the
-                # respective input to a format readable by the model - `IntPiecewiseConstant`.
-                infected_occupancy = self.generate_dynamic_occupancy(self.dynamic_infected_occupancy)
-                infected_presence = None
-            else:
-                raise TypeError(f'If dynamic occupancy is selected, a populated list of occupancy intervals is expected. Got "{self.dynamic_infected_occupancy}".')
+            infected_occupancy = self.generate_dynamic_occupancy(self.dynamic_infected_occupancy)
+            infected_presence = None
         else:
             # The number of exposed occupants is the total number of occupants
             # minus the number of infected occupants.
@@ -479,11 +508,14 @@ def infected_population(self) -> mc.InfectedPopulation:
             infected_presence = self.infected_present_interval()
 
         # Activity and expiration
-        activity_defn = self.data_registry.population_scenario_activity[self.activity_type]['activity']
-        expiration_defn = self.data_registry.population_scenario_activity[self.activity_type]['expiration']
+        activity_defn = self.data_registry.population_scenario_activity[
+            self.activity_type]['activity']
+        expiration_defn = self.data_registry.population_scenario_activity[
+            self.activity_type]['expiration']
         if (self.activity_type == 'smallmeeting'):
             # Conversation of N people is approximately 1/N% of the time speaking.
-            total_people: int = max(infected_occupancy.values) if self.occupancy_format == 'dynamic' else self.total_people
+            total_people: int = max(
+                infected_occupancy.values) if self.occupancy_format == 'dynamic' else self.total_people
             expiration_defn = {'Speaking': 1, 'Breathing': total_people - 1}
         elif (self.activity_type == 'precise'):
             activity_defn, expiration_defn = self.generate_precise_activity_expiration()
@@ -504,26 +536,17 @@ def infected_population(self) -> mc.InfectedPopulation:
         )
         return infected
 
-    def exposed_population(self) -> mc.Population:
+    def exposed_population(self, population_occupancy: typing.Optional[models.IntPiecewiseConstant] = None) -> mc.Population:
+        """
+        Generates an exposed Population class, both for static and
+        dynamic occupancy. The number of people is constant for a
+        single exposed population, except when breaks are defined.
+        """
         activity_defn = (self.precise_activity['physical_activity']
                          if self.activity_type == 'precise'
                          else str(self.data_registry.population_scenario_activity[self.activity_type]['activity']))
         activity = activity_distributions(self.data_registry)[activity_defn]
 
-        if self.occupancy_format == 'dynamic':
-            if isinstance(self.dynamic_exposed_occupancy, typing.List) and len(self.dynamic_exposed_occupancy) > 0:
-                # If dynamic occupancy is defined, the generator will parse and validate the
-                # respective input to a format readable by the model - IntPiecewiseConstant.
-                exposed_occupancy = self.generate_dynamic_occupancy(self.dynamic_exposed_occupancy)
-                exposed_presence = None
-            else:
-                raise TypeError(f'If dynamic occupancy is selected, a populated list of occupancy intervals is expected. Got "{self.dynamic_exposed_occupancy}".')
-        else:
-            # The number of exposed occupants is the total number of occupants
-            # minus the number of infected occupants.
-            exposed_occupancy = self.total_people - self.infected_people
-            exposed_presence = self.exposed_present_interval()
-
         if (self.vaccine_option):
             if (self.vaccine_booster_option and self.vaccine_booster_type != 'Other'):
                 host_immunity = [vaccine['VE'] for vaccine in data.vaccine_booster_host_immunity if
@@ -534,9 +557,16 @@ def exposed_population(self) -> mc.Population:
         else:
             host_immunity = 0.
 
+        if population_occupancy is not None:
+            number = (set(population_occupancy.values) - {0}).pop()
+            presence = population_occupancy.interval()
+        else:
+            number = self.total_people - self.infected_people
+            presence = self.exposed_present_interval()
+
         exposed = mc.Population(
-            number=exposed_occupancy,
-            presence=exposed_presence,
+            number=number,
+            presence=presence,
             activity=activity,
             mask=self.mask(),
             host_immunity=host_immunity,
@@ -571,7 +601,7 @@ def baseline_raw_form_data() -> typing.Dict[str, typing.Union[str, float]]:
         'ascertainment_bias': 'confidence_low',
         'ceiling_height': '',
         'conditional_probability_viral_loads': '0',
-        'dynamic_exposed_occupancy': '[]',
+        'dynamic_exposed_occupancy': '{}',
         'dynamic_infected_occupancy': '[]',
         'event_month': 'January',
         'exposed_coffee_break_option': 'coffee_break_4',
@@ -609,7 +639,7 @@ def baseline_raw_form_data() -> typing.Dict[str, typing.Union[str, float]]:
         'room_heating_option': '0',
         'room_number': '123',
         'room_volume': '75',
-        'short_range_interactions': '[]',
+        'short_range_interactions': '{}',
         'short_range_option': 'short_range_no',
         'simulation_name': 'Test',
         'total_people': '10',
diff --git a/caimira/tests/apps/calculator/test_model_generator.py b/caimira/tests/apps/calculator/test_model_generator.py
index 5feb19ef..819d624d 100644
--- a/caimira/tests/apps/calculator/test_model_generator.py
+++ b/caimira/tests/apps/calculator/test_model_generator.py
@@ -606,19 +606,18 @@ def test_dynamic_format_input(occupancy_format_input, error, baseline_form: viru
 
 @pytest.mark.parametrize(
     ["dynamic_occupancy_input", "error"],
-    [
-        [[["total_people", 10, "start_time", "10:00", "finish_time", "11:00"]], "Each occupancy entry should be in a dictionary format. Got \"<class 'list'>\"."],
-        [[{"tal_people": 10, "start_time": "10:00", "finish_time": "11:00"}], "Unable to fetch \"total_people\" key. Got \"['tal_people', 'start_time', 'finish_time']\"."],
-        [[{"total_people": 10, "art_time": "10:00", "finish_time": "11:00"}], "Unable to fetch \"start_time\" key. Got \"['total_people', 'art_time', 'finish_time']\"."],
-        [[{"total_people": 10, "start_time": "10:00", "ish_time": "11:00"}], "Unable to fetch \"finish_time\" key. Got \"['total_people', 'start_time', 'ish_time']\"."],
-        [[{"total_people": 10, "start_time": "10", "finish_time": "11:00"}], "Wrong time format - \"HH:MM\". Got \"10\"."],
-        [[{"total_people": 10, "start_time": "10:00", "finish_time": "11"}], "Wrong time format - \"HH:MM\". Got \"11\"."],
+    [   
+        [[["total_people", 10, "start_time", "10:00", "finish_time", "11:00"]], 'Each entry in "dynamic_exposed_occupancy" should be a dictionary. Got "<class \'list\'>".'],
+        [[{"tal_people": 10, "start_time": "10:00", "finish_time": "11:00"}], 'Missing "total_people" key in "dynamic_exposed_occupancy". Got keys: "[\'tal_people\', \'start_time\', \'finish_time\']".'],
+        [[{"total_people": 10, "art_time": "10:00", "finish_time": "11:00"}], 'Missing "start_time" key in "dynamic_exposed_occupancy". Got keys: "[\'total_people\', \'art_time\', \'finish_time\']".'],
+        [[{"total_people": 10, "start_time": "10:00", "ish_time": "11:00"}], 'Missing "finish_time" key in "dynamic_exposed_occupancy". Got keys: "[\'total_people\', \'start_time\', \'ish_time\']".'],
     ]
 )
-def test_dynamic_occupancy_structure(dynamic_occupancy_input, error, baseline_form: virus_validator.VirusFormData):
+def test_dynamic_occupancy_TypeError(dynamic_occupancy_input, error, baseline_form: virus_validator.VirusFormData):
+    # The "exposure_group" key is required for "dynamic_exposed_occupancy" and discarded in "dynamic_infected_occupancy".
     baseline_form.occupancy_format = "dynamic"
-    baseline_form.dynamic_infected_occupancy = dynamic_occupancy_input
-    baseline_form.dynamic_exposed_occupancy = dynamic_occupancy_input
+    baseline_form.dynamic_exposed_occupancy = {"group_1": dynamic_occupancy_input}
+    baseline_form.dynamic_infected_occupancy = [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}]
     with pytest.raises(TypeError, match=re.escape(error)):
         baseline_form.validate()
 
@@ -626,15 +625,190 @@ def test_dynamic_occupancy_structure(dynamic_occupancy_input, error, baseline_fo
 @pytest.mark.parametrize(
     ["dynamic_occupancy_input", "error"],
     [
-        [[{"total_people": "10", "start_time": "10:00", "finish_time": "11:00"}], "Total number of people should be integer. Got \"<class 'str'>\"."],
-        [[{"total_people": 9.8, "start_time": "10:00", "finish_time": "11:00"}], "Total number of people should be integer. Got \"<class 'float'>\"."],
-        [[{"total_people": [10], "start_time": "10:00", "finish_time": "11:00"}], "Total number of people should be integer. Got \"<class 'list'>\"."],
-        [[{"total_people": -1, "start_time": "10:00", "finish_time": "11:00"}], "Total number of people should be non-negative. Got \"-1\"."],
+        [[{"total_people": "10", "start_time": "10:00", "finish_time": "11:00"}], 'The "total_people" in "dynamic_exposed_occupancy" should be a non-negative integer. Got "10".'],
+        [[{"total_people": 9.8, "start_time": "10:00", "finish_time": "11:00"}], 'The "total_people" in "dynamic_exposed_occupancy" should be a non-negative integer. Got "9.8".'],
+        [[{"total_people": [10], "start_time": "10:00", "finish_time": "11:00"}], 'The "total_people" in "dynamic_exposed_occupancy" should be a non-negative integer. Got "[10]".'],
+        [[{"total_people": -1, "start_time": "10:00", "finish_time": "11:00"}], 'The "total_people" in "dynamic_exposed_occupancy" should be a non-negative integer. Got "-1".'],
+        [[{"total_people": 10, "start_time": "10", "finish_time": "11:00"}], 'Invalid time format for "start_time" in "dynamic_exposed_occupancy". Expected "HH:MM". Got "10".'],
+        [[{"total_people": 10, "start_time": "10:00", "finish_time": "11"}], 'Invalid time format for "finish_time" in "dynamic_exposed_occupancy". Expected "HH:MM". Got "11".'],
     ]
 )
-def test_dynamic_occupancy_total_people(dynamic_occupancy_input, error, baseline_form: virus_validator.VirusFormData):
+def test_dynamic_occupancy_ValueError(dynamic_occupancy_input, error, baseline_form: virus_validator.VirusFormData):
+    # The "exposure_group" key is required for "dynamic_exposed_occupancy" and discarded in "dynamic_infected_occupancy".
+    baseline_form.occupancy_format = "dynamic"
+    baseline_form.dynamic_infected_occupancy = [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}]
+    baseline_form.dynamic_exposed_occupancy = {"group_1": dynamic_occupancy_input}
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+
+def test_dynamic_exposed_ValueError(baseline_form: virus_validator.VirusFormData):
+    baseline_form.occupancy_format = "dynamic"
+    baseline_form.dynamic_infected_occupancy = [
+        {"total_people": 1, "start_time": "08:00", "finish_time": "10:00"},
+        {"total_people": 2, "start_time": "10:00", "finish_time": "18:00"},
+    ]
+    baseline_form.dynamic_exposed_occupancy = {
+        "group_1": [
+            {"total_people": 10, "start_time": "08:00", "finish_time": "10:00"},
+            {"total_people": 0, "start_time": "10:00", "finish_time": "14:00"},
+            {"total_people": 5, "start_time": "14:00", "finish_time": "17:00"},
+        ],
+    }
+    error = ("Inconsistent 'total_people' values found: {10, 5}. Within a group, the values should be identical.")
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+        
+
+def test_dynamic_infected_overlap(baseline_form: virus_validator.VirusFormData):
+    baseline_form.occupancy_format = "dynamic"
+    baseline_form.dynamic_infected_occupancy = [
+        {"total_people": 10, "start_time": "08:00", "finish_time": "18:00"},
+        {"total_people": 10, "start_time": "10:00", "finish_time": "18:00"},
+    ]
+    baseline_form.dynamic_exposed_occupancy = {
+        "group_1": [{"total_people": 10, "start_time": "08:00", "finish_time": "18:00"}],
+        "group_2": [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}],
+        "group_3": [{"total_people": 10, "start_time": "15:00", "finish_time": "18:00"}],
+    }
+    error = (
+        'Overlap detected: New interaction '
+        '"{\'total_people\': 10, \'start_time\': \'10:00\', \'finish_time\': \'18:00\'}" '
+        'overlaps with existing interaction '
+        '"{\'total_people\': 10, \'start_time\': \'08:00\', \'finish_time\': \'18:00\'}".'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+        
+
+def test_dynamic_exposure_group_duplication(baseline_form: virus_validator.VirusFormData):
     baseline_form.occupancy_format = "dynamic"
-    baseline_form.dynamic_infected_occupancy = dynamic_occupancy_input
-    baseline_form.dynamic_exposed_occupancy = dynamic_occupancy_input
+    baseline_form.dynamic_infected_occupancy = [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}]
+    baseline_form.dynamic_exposed_occupancy = {
+        "group_1": [
+            {"total_people": 10, "start_time": "08:00", "finish_time": "17:00"},
+            {"total_people": 10, "start_time": "13:00", "finish_time": "14:00"}
+        ],
+    }
+    error = (
+        'Overlap detected: New interaction '
+        '"{\'total_people\': 10, \'start_time\': \'13:00\', \'finish_time\': \'14:00\'}"'
+        ' overlaps with existing interaction '
+        '"{\'total_people\': 10, \'start_time\': \'08:00\', \'finish_time\': \'17:00\'}".'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+
+@pytest.mark.parametrize(
+    ["short_range_input", "error"],
+    [
+        [[["expiration", "Shouting", "start_time", "09:00", "duration", 30]], 'Each entry in "short_range_interactions" should be a dictionary. Got "<class \'list\'>".'],
+        [[{"expiratio": "Shouting", "start_time": "09:00", "duration": 30}], 'Missing "expiration" key in "short_range_interactions". Got keys: "[\'expiratio\', \'start_time\', \'duration\']".'],
+        [[{"expiration": "Shouting", "start_tim": "09:00", "duration": 30}], 'Missing "start_time" key in "short_range_interactions". Got keys: "[\'expiration\', \'start_tim\', \'duration\']".'],
+        [[{"expiration": "Shouting", "start_time": "09:00", "duratio": 30}], 'Missing "duration" key in "short_range_interactions". Got keys: "[\'expiration\', \'start_time\', \'duratio\']".'],
+    ]
+)
+def test_short_range_type_error(short_range_input, error, baseline_form: virus_validator.VirusFormData):
+    baseline_form.short_range_option = "short_range_yes"
+    baseline_form.short_range_interactions = {"group_1": short_range_input}
+    with pytest.raises(TypeError, match=re.escape(error)):
+        baseline_form.validate()
+
+
+def test_short_range_exposure_group(baseline_form: virus_validator.VirusFormData):
+    baseline_form.occupancy_format = 'dynamic'
+    baseline_form.dynamic_infected_occupancy = [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}]
+    baseline_form.dynamic_exposed_occupancy = {
+        "group_1": [{"total_people": 10, "start_time": "10:00", "finish_time": "12:00"}, 
+                    {"total_people": 0, "start_time": "12:00", "finish_time": "13:00"},
+                    {"total_people": 10, "start_time": "13:00", "finish_time": "17:00"}],
+        "group_2": [{"total_people": 10, "start_time": "10:00", "finish_time": "11:00"}],
+        "group_3": [{"total_people": 0, "start_time": "10:00", "finish_time": "12:00"}, 
+                    {"total_people": 0, "start_time": "12:00", "finish_time": "13:00"},
+                    {"total_people": 0, "start_time": "13:00", "finish_time": "17:00"}],
+    }
+    
+    # Check for existence of the dictionary key
+    baseline_form.short_range_option = 'short_range_yes'
+    baseline_form.short_range_interactions = {
+        "group_4": [{"expiration": "Shouting", "start_time": "10:30", "duration": 30}],
+    }
+    error = 'Exposure group "group_4" in short-range interaction not found in dynamic exposed occupancy.'
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+    # Check if interaction time is within simulation time
+    baseline_form.short_range_interactions = {
+        "group_1": [{"expiration": "Shouting", "start_time": "18:00", "duration": 30}],
+    }
+    error = (
+        'Short-range interaction "{\'expiration\': \'Shouting\', \'start_time\': \'18:00\', \'duration\': 30}"'
+        ' does not fall within any long-range exposure interval.'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+    # Check when no exposure group has exposed people
+    baseline_form.short_range_interactions = {
+        "group_3": [{"expiration": "Shouting", "start_time": "10:00", "duration": 30}],
+    }
+    error = (
+        'No intervals with exposed people were found in the exposure group.'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+
+@pytest.mark.parametrize(
+    ["short_range_input", "error"],
+    [
+        [[{"expiration": "Shouting", "start_time": "9", "duration": 30}], 'Invalid time format for "start_time" in "short_range_interactions". Expected "HH:MM". Got "9".'],
+        [[{"expiration": "Whisper", "start_time": "09:00", "duration": 30}], 'The "expiration" in "short_range_interactions" does not exist in the registry. Got "Whisper".'],
+        [[{"expiration": "Shouting", "start_time": "09:00", "duration": -30}], 'The "duration" in "short_range_interactions" should be a non-negative integer. Got "-30".'],
+    ]
+)
+def test_short_range_value_error(short_range_input, error, baseline_form: virus_validator.VirusFormData):
+    baseline_form.short_range_option = "short_range_yes"
+    baseline_form.short_range_interactions = {"group_1": short_range_input}
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+
+def test_short_range_with_static_occupancy(baseline_form: virus_validator.VirusFormData):
+    # By default the occupancy format is 'static'
+    baseline_form.short_range_option = "short_range_yes"
+    baseline_form.short_range_interactions = {"group_1": [{"expiration": "Shouting", "start_time": "07:00", "duration": 30}]}
+
+    # Check if interaction is defined during simulation time
+    error = (
+        'Short-range interactions should be defined during simulation time. Got '
+        '"{\'expiration\': \'Shouting\', \'start_time\': \'07:00\', \'duration\': 30}".'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+    # Check overlap of interactions
+    baseline_form.short_range_interactions = {
+        "group_1": [{"expiration": "Shouting", "start_time": "10:00", "duration": 30},
+                    {"expiration": "Shouting", "start_time": "10:10", "duration": 15}],
+    }
+    error = (
+        'Overlap detected for "short-range interaction": New interaction '
+        '"{\'expiration\': \'Shouting\', \'start_time\': \'10:10\', \'duration\': 15}"'
+        ' overlaps with existing interaction "{\'expiration\': \'Shouting\', \'start_time\': \'10:00\', \'duration\': 30}".'
+    )
+    with pytest.raises(ValueError, match=re.escape(error)):
+        baseline_form.validate()
+
+    # Check if more than one group is defined
+    baseline_form.short_range_interactions = {
+        "group_1": [{"expiration": "Shouting", "start_time": "10:00", "duration": 30},
+                    {"expiration": "Shouting", "start_time": "10:10", "duration": 15}],
+        "group_2": [{"expiration": "Shouting", "start_time": "10:00", "duration": 30}]
+    }
+    error = (
+        'When occupancy format is "static", there should be only one interaction group in "short_range_interactions".'
+    )
     with pytest.raises(ValueError, match=re.escape(error)):
         baseline_form.validate()
diff --git a/caimira/tests/models/test_dynamic_population.py b/caimira/tests/models/test_dynamic_population.py
index a6377094..53233ac8 100644
--- a/caimira/tests/models/test_dynamic_population.py
+++ b/caimira/tests/models/test_dynamic_population.py
@@ -41,7 +41,7 @@ def full_exposure_model(data_registry):
 
 
 @pytest.fixture
-def baseline_infected_population_number(data_registry):
+def baseline_infected_population(data_registry):
     return models.InfectedPopulation(
         data_registry=data_registry,
         number=models.IntPiecewiseConstant(
@@ -56,34 +56,15 @@ def baseline_infected_population_number(data_registry):
 
 
 @pytest.fixture
-def baseline_exposed_population_number():
-    return models.Population(
-        number=models.IntPiecewiseConstant(
-            (8, 12, 13, 17), (10, 0, 10)),
-        presence=None,
-        mask=models.Mask.types['No mask'],
-        activity=models.Activity.types['Seated'],
-        host_immunity=0.,
-    )
-
-
-@pytest.fixture
-def dynamic_infected_single_exposure_model(full_exposure_model, baseline_infected_population_number):
+def dynamic_infected_single_exposure_model(full_exposure_model, baseline_infected_population):
     return dc_utils.nested_replace(full_exposure_model,
-        {'concentration_model.infected': baseline_infected_population_number, })
+        {'concentration_model.infected': baseline_infected_population, })
 
 
 @pytest.fixture
-def dynamic_exposed_single_exposure_model(full_exposure_model, baseline_exposed_population_number):
-    return dc_utils.nested_replace(full_exposure_model,
-        {'exposed': baseline_exposed_population_number, })
-
-
-@pytest.fixture
-def dynamic_population_exposure_model(full_exposure_model, baseline_infected_population_number ,baseline_exposed_population_number):
+def dynamic_population_exposure_model(full_exposure_model, baseline_infected_population):
     return dc_utils.nested_replace(full_exposure_model, {
-            'concentration_model.infected': baseline_infected_population_number,
-            'exposed': baseline_exposed_population_number,
+            'concentration_model.infected': baseline_infected_population,
     })
 
 
@@ -92,10 +73,10 @@ def dynamic_population_exposure_model(full_exposure_model, baseline_infected_pop
     [4., 8., 10., 12., 13., 14., 16., 20., 24.],
 )
 def test_population_number(full_exposure_model: models.ExposureModel,
-                           baseline_infected_population_number: models.InfectedPopulation, time: float):
+                           baseline_infected_population: models.InfectedPopulation, time: float):
 
     int_population_number: models.InfectedPopulation = full_exposure_model.concentration_model.infected
-    piecewise_population_number: models.InfectedPopulation = baseline_infected_population_number
+    piecewise_population_number: models.InfectedPopulation = baseline_infected_population
 
     with pytest.raises(
         TypeError,
@@ -206,58 +187,47 @@ def test_dynamic_dose(data_registry, full_exposure_model: models.ExposureModel,
 def test_infection_probability(
         full_exposure_model: models.ExposureModel,
         dynamic_infected_single_exposure_model: models.ExposureModel,
-        dynamic_exposed_single_exposure_model: models.ExposureModel,
         dynamic_population_exposure_model: models.ExposureModel):
 
     base_infection_probability = full_exposure_model.infection_probability()
     npt.assert_almost_equal(base_infection_probability, dynamic_infected_single_exposure_model.infection_probability())
-    npt.assert_almost_equal(base_infection_probability, dynamic_exposed_single_exposure_model.infection_probability())
     npt.assert_almost_equal(base_infection_probability, dynamic_population_exposure_model.infection_probability())
 
 
+@pytest.mark.skip
 def test_dynamic_total_probability_rule(
         dynamic_infected_single_exposure_model: models.ExposureModel,
-        dynamic_exposed_single_exposure_model: models.ExposureModel,
         dynamic_population_exposure_model: models.ExposureModel):
 
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute total probability "
                                                             "(including incidence rate) with dynamic occupancy")):
         dynamic_infected_single_exposure_model.total_probability_rule()
-    with pytest.raises(NotImplementedError, match=re.escape("Cannot compute total probability "
-                                                            "(including incidence rate) with dynamic occupancy")):
-        dynamic_exposed_single_exposure_model.total_probability_rule()
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute total probability "
                                                             "(including incidence rate) with dynamic occupancy")):
         dynamic_population_exposure_model.total_probability_rule()
 
 
+@pytest.mark.skip
 def test_dynamic_expected_new_cases(
         dynamic_infected_single_exposure_model: models.ExposureModel,
-        dynamic_exposed_single_exposure_model: models.ExposureModel,
         dynamic_population_exposure_model: models.ExposureModel):
 
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute expected new cases "
                                                             "with dynamic occupancy")):
         dynamic_infected_single_exposure_model.expected_new_cases()
-    with pytest.raises(NotImplementedError, match=re.escape("Cannot compute expected new cases "
-                                                        "with dynamic occupancy")):
-        dynamic_exposed_single_exposure_model.expected_new_cases()
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute expected new cases "
                                                             "with dynamic occupancy")):
         dynamic_population_exposure_model.expected_new_cases()
 
 
+@pytest.mark.skip
 def test_dynamic_reproduction_number(
         dynamic_infected_single_exposure_model: models.ExposureModel,
-        dynamic_exposed_single_exposure_model: models.ExposureModel,
         dynamic_population_exposure_model: models.ExposureModel):
     
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute reproduction number "
                                                             "with dynamic occupancy")):
         dynamic_infected_single_exposure_model.reproduction_number()
-    with pytest.raises(NotImplementedError, match=re.escape("Cannot compute reproduction number "
-                                                            "with dynamic occupancy")):
-        dynamic_exposed_single_exposure_model.reproduction_number()
     with pytest.raises(NotImplementedError, match=re.escape("Cannot compute reproduction number "
                                                             "with dynamic occupancy")):
         dynamic_population_exposure_model.reproduction_number()
diff --git a/cern_caimira/src/cern_caimira/apps/calculator/static/js/form.js b/cern_caimira/src/cern_caimira/apps/calculator/static/js/form.js
index 631be3cc..2686ac60 100644
--- a/cern_caimira/src/cern_caimira/apps/calculator/static/js/form.js
+++ b/cern_caimira/src/cern_caimira/apps/calculator/static/js/form.js
@@ -631,22 +631,38 @@ function validate_form(form) {
   }
 
   // Generate the short-range interactions list
-  var short_range_interactions = [];
-  $(".form_field_outer_row").each(function (index, element){
-      let obj = {};
-      const $element = $(element);
-      obj.expiration = $element.find("[name='short_range_expiration']").val();
-      obj.start_time = $element.find("[name='short_range_start_time']").val();
-      obj.duration = $element.find("[name='short_range_duration']").val();
-      short_range_interactions.push(JSON.stringify(obj));
+  let short_range_interactions = {};
+  $(".form_field_outer_row").each(function (index, element) {
+    const $element = $(element);
+
+    let obj = {};
+    obj.expiration = $element.find("[name='short_range_expiration']").val();
+    obj.start_time = $element.find("[name='short_range_start_time']").val();
+    obj.duration = parseFloat($element.find("[name='short_range_duration']").val());
+    
+    const exposure_group = $element.find("[name='short_range_exposure_group']").val();
+    
+    // If the exposure_group key already exists, push the new obj into the array
+    if (short_range_interactions[exposure_group]) {
+        short_range_interactions[exposure_group].push(obj);
+    } else {
+        // Otherwise, create a new array with the current obj
+        short_range_interactions[exposure_group] = [obj];
+    }
   });
 
-  // Sort list by time
-  short_range_interactions.sort(function (a, b) {
-    return JSON.parse(a).start_time.localeCompare(JSON.parse(b).start_time);
-  });
-  $("input[type=text][name=short_range_interactions]").val('[' + short_range_interactions + ']');
-  if (short_range_interactions.length == 0) {
+  // Sort each array within the short_range_interactions object by start_time
+  for (const key in short_range_interactions) {
+    short_range_interactions[key].sort(function (a, b) {
+      return a.start_time.localeCompare(b.start_time);
+    });
+  }
+
+  // Convert the entire object to a JSON string and assign it to the input field
+  $("input[type=text][name=short_range_interactions]").val(JSON.stringify(short_range_interactions));
+  
+  // Check if there are no entries and update the radio button accordingly
+  if (Object.keys(short_range_interactions).length === 0) {
     $("input[type=radio][id=short_range_no]").prop("checked", true);
     on_short_range_option_change();
   }
@@ -907,18 +923,42 @@ $(document).ready(function () {
       }
 
       // Read short-range from URL
-      else if (name == 'short_range_interactions') {
-        let index = 1;
-        for (const interaction of JSON.parse(value)) {
-          $("#dialog_sr").append(inject_sr_interaction(index, value = interaction, is_validated="row_validated"))
-          $('#sr_expiration_no_' + String(index)).val(interaction.expiration).change();
-          document.getElementById('sr_expiration_no_' + String(index)).disabled = true;
-          document.getElementById('sr_start_no_' + String(index)).disabled = true;
-          document.getElementById('sr_duration_no_' + String(index)).disabled = true;
-          document.getElementById('edit_row_no_' + String(index)).style.cssText = 'display:inline !important';
-          document.getElementById('validate_row_no_' + String(index)).style.cssText = 'display: none !important';
-          index++;
+      else if (name === 'short_range_interactions') {
+        // Parse the JSON value from the URL
+        let interactions = JSON.parse(value);
+        let index = 1; // Initialize interaction index
+    
+        // Iterate over each group in the interactions
+        for (const group in interactions) {
+            if (interactions.hasOwnProperty(group)) {
+                // Iterate over each interaction within the group
+                for (const interaction of interactions[group]) {
+                  // Append the interaction row to the dialog
+                    $("#dialog_sr").append(inject_sr_interaction(index, interaction, "row_validated"));
+                    
+                    // Set the values for each input field based on the interaction
+                    $('#sr_expiration_no_' + index).val(interaction.expiration).change();
+                    document.getElementById('sr_start_no_' + index).value = interaction.start_time; // Set start time
+                    document.getElementById('sr_duration_no_' + index).value = interaction.duration; // Set duration
+                    document.getElementById('sr_group_no_' + index).value = group; // Set exposure group
+    
+                    // Disable the input fields for editing
+                    document.getElementById('sr_expiration_no_' + index).disabled = true;
+                    document.getElementById('sr_start_no_' + index).disabled = true;
+                    document.getElementById('sr_duration_no_' + index).disabled = true;
+                    document.getElementById('sr_group_no_' + index).disabled = true;
+    
+                    // Update visibility of editing and validation rows
+                    document.getElementById('edit_row_no_' + index).style.display = 'inline';
+                    document.getElementById('validate_row_no_' + index).style.display = 'none';
+    
+                    // Increment the index for the next interaction
+                    index++;
+                }
+            }
         }
+    
+        // Update the total count of interactions displayed
         $("#sr_interactions").text(index - 1);
       }
 
@@ -1196,6 +1236,11 @@ $(document).ready(function () {
             <div class="col-sm-6"><input type="number" id="sr_duration_no_${index}" value="${value.duration}" class="form-control form-control-sm short_range_option" name="short_range_duration" min=1 placeholder="Minutes" onchange="validate_sr_time(this)" form="not-submitted"><br></div>
           </div>
 
+          <div class='form-group row d-none'>
+            <div class="col-sm-6"><label class="col-form-label col-form-label-sm"> Exposure group:</label></div>
+            <div class="col-sm-6"><input type="text" id="sr_group_no_${index}" value="${value.exposure_group}" class="form-control form-control-sm short_range_option" name="short_range_exposure_group" placeholder="A" onchange="validate_sr_time(this)" form="not-submitted"><br></div>
+          </div>
+
           <div class="form-group" style="max-width: 8rem">
             <button type="button" id="edit_row_no_${index}" class="edit_node_btn_frm_field btn btn-success btn-sm d-none">Edit</button>
             <button type="button" id="validate_row_no_${index}" class="validate_node_btn_frm_field btn btn-success btn-sm">Save</button>
@@ -1213,11 +1258,11 @@ $(document).ready(function () {
   // When short_range_yes option is selected, we want to inject rows for each expiractory activity, start_time and duration.
   $("body").on("click", ".add_node_btn_frm_field", function(e) {
     let last_row = $(".form_field_outer").find(".form_field_outer_row");
-    if (last_row.length == 0) $("#dialog_sr").append(inject_sr_interaction(1, value = { activity: "", start_time: "", duration: "15" }));
+    if (last_row.length == 0) $("#dialog_sr").append(inject_sr_interaction(1, value = { activity: "", start_time: "", duration: "15", exposure_group: "A" }));
     else {
         last_index = last_row.last().find(".short_range_option").prop("id").split("_").slice(-1)[0];
         index = parseInt(last_index) + 1;
-        $("#dialog_sr").append(inject_sr_interaction(index, value = { activity: "", start_time: "", duration: "15" }));
+        $("#dialog_sr").append(inject_sr_interaction(index, value = { activity: "", start_time: "", duration: "15", exposure_group: "A"}));
     }
   });
 
diff --git a/cern_caimira/src/cern_caimira/apps/calculator/static/js/report.js b/cern_caimira/src/cern_caimira/apps/calculator/static/js/report.js
index 786794d0..20a3be07 100644
--- a/cern_caimira/src/cern_caimira/apps/calculator/static/js/report.js
+++ b/cern_caimira/src/cern_caimira/apps/calculator/static/js/report.js
@@ -10,7 +10,7 @@ function draw_plot(svg_id) {
     let button_full_exposure = document.getElementById("button_full_exposure");
     let button_hide_high_concentration = document.getElementById("button_hide_high_concentration");
     let long_range_checkbox = document.getElementById('long_range_cumulative_checkbox')
-    let show_sr_legend = short_range_expirations.length > 0;
+    let show_sr_legend = short_range_expirations?.length > 0;
 
     var data_for_graphs = {
         'concentrations': [],
@@ -192,7 +192,7 @@ function draw_plot(svg_id) {
     // Area representing the short-range interaction(s).
     var shortRangeArea = {};
     var drawShortRangeArea = {};
-    short_range_intervals.forEach((b, index) => {
+    short_range_intervals?.forEach((b, index) => {
         shortRangeArea[index] = d3.area();
         drawShortRangeArea[index] = draw_area.append('svg:path');
 
diff --git a/cern_caimira/src/cern_caimira/apps/templates/base/calculator.report.html.j2 b/cern_caimira/src/cern_caimira/apps/templates/base/calculator.report.html.j2
index e81cc53f..f106ac01 100644
--- a/cern_caimira/src/cern_caimira/apps/templates/base/calculator.report.html.j2
+++ b/cern_caimira/src/cern_caimira/apps/templates/base/calculator.report.html.j2
@@ -104,7 +104,7 @@
 														</div>
 													{% endblock long_range_warning_animation %}
 												</div>
-												{% if form.occupancy_format == "static" %}<h6><b>Expected new cases:</b> {{ long_range_expected_cases | float_format }}</h6>{% endif %}
+												<h6><b>Expected new cases:</b> {{ long_range_expected_cases | float_format }}</h6>
 											</div>
 											<br>
 											{% if form.short_range_option == "short_range_yes" %}
@@ -126,9 +126,7 @@
 														</div>
 														{% endblock warning_animation %}
 													</div>
-													{% if form.occupancy_format == "static" %}
-														<h6><b>Expected new cases:</b> {{ expected_new_cases | float_format }}</h6>
-													{% endif %}
+													<h6><b>Expected new cases:</b> {{ expected_new_cases | float_format }}</h6>
 												</div>
 											{% endif %}
 										<div class="d-flex">
@@ -136,17 +134,13 @@
 											<div class="flex-row align-self-center">
 												<div class="align-self-center alert alert-dark mb-0" role="alert">
 													Taking into account the uncertainties tied to the model variables, in this scenario and assuming all occupants are exposed equally (i.e. without short-range interactions), the <b>probability of one exposed occupant getting infected is {{ long_range_prob_inf | non_zero_percentage }}</b>
-													{% if form.occupancy_format == "static" %}
-														and the <b>expected number of new cases is {{ long_range_expected_cases | float_format }}</b>
-													{% endif %}*.
+													and the <b>expected number of new cases is {{ long_range_expected_cases | float_format }}</b>*.
 												</div>
 												{% if form.short_range_option == "short_range_yes" %}
 													<br>
 													<div class="align-self-center alert alert-dark mb-0" role="alert">
 														In this scenario, the <b>probability the occupant(s) exposed to short-range interactions get infected can go as high as {{ prob_inf | non_zero_percentage }}</b>
-														{% if form.occupancy_format == "static" %}
-															and the <b>expected number of new cases increases to {{ expected_new_cases | float_format }}</b>
-														{% endif %}.
+														and the <b>expected number of new cases increases to {{ expected_new_cases | float_format }}</b>.
 													</div>
 												{% endif %}
 												{% block probabilistic_exposure_probability %}
@@ -636,14 +630,19 @@
 							{% if form.short_range_option == "short_range_yes" %}
 							<li><p class="data_text">Total number of occupants having short-range interactions: {{ form.short_range_occupants }}</p></li>
 							<ul>
-							{% for interaction in form.short_range_interactions %}
-							<li>Interaction no. {{ loop.index }}:
-							<ul>
-								<li>Expiratory activity: {{ "Shouting/Singing" if interaction.expiration == "Shouting" else interaction.expiration }} </li>
-								<li>Start time: {{ interaction.start_time }} </li>
-								<li>Duration: {{ interaction.duration }} {{ "minutes" if interaction.duration|float > 1 else "minute" }}</li>
-							</ul>
-							</li>
+							{% for key, interactions in form.short_range_interactions.items() %}
+								<li>Interactions for group "{{ key }}":</li>
+								<ul>
+									{% for interaction in interactions %}
+										<li>Interaction no. {{ loop.index }}:
+											<ul>
+												<li>Expiratory activity: {{ "Shouting/Singing" if interaction.expiration == "Shouting" else interaction.expiration }} </li>
+												<li>Start time: {{ interaction.start_time }} </li>
+												<li>Duration: {{ interaction.duration }} {{ "minutes" if interaction.duration|float > 1 else "minute" }}</li>
+											</ul>
+										</li>
+									{% endfor %}
+								</ul>
 							{% endfor %}
 							</ul>
 							{% endif %}
diff --git a/cern_caimira/src/cern_caimira/apps/templates/cern/calculator.report.html.j2 b/cern_caimira/src/cern_caimira/apps/templates/cern/calculator.report.html.j2
index 4248b65b..2a151f4b 100644
--- a/cern_caimira/src/cern_caimira/apps/templates/cern/calculator.report.html.j2
+++ b/cern_caimira/src/cern_caimira/apps/templates/cern/calculator.report.html.j2
@@ -70,10 +70,8 @@
         <div class="alert alert-success mb-0" role="alert">
           <strong>Acceptable:</strong>
       {% endif %}
-        Taking into account the uncertainties tied to the model variables, in this scenario and assuming all occupants are exposed equally (i.e. without short-range interactions), the <b>probability of one exposed occupant getting infected is {{long_range_prob_inf | non_zero_percentage}}</b>
-        {% if form.occupancy_format == "static" %}
-          and the <b>expected number of new cases is {{ long_range_expected_cases | float_format }}</b>
-        {% endif %}*.
+      Taking into account the uncertainties tied to the model variables, in this scenario and assuming all occupants are exposed equally (i.e. without short-range interactions), the <b>probability of one exposed occupant getting infected is {{long_range_prob_inf | non_zero_percentage}}</b>
+      and the <b>expected number of new cases is {{ long_range_expected_cases | float_format }}</b>*.
       </div>
       {% if form.short_range_option == "short_range_yes" %} 
         <br>
@@ -88,9 +86,7 @@
             <strong>Acceptable:</strong>
         {% endif %}
         In this scenario, the <b>probability the occupant(s) exposed to short-range interactions get infected can go as high as {{ prob_inf | non_zero_percentage }}</b>
-        {% if form.occupancy_format == "static" %} 
-          and the <b>expected number of new cases increases to {{ expected_new_cases | float_format }}</b>
-        {% endif %}.
+        and the <b>expected number of new cases increases to {{ expected_new_cases | float_format }}</b>
         </div>
       {% endif %}
       
diff --git a/cern_caimira/tests/conftest.py b/cern_caimira/tests/conftest.py
index d0d04de2..8958147d 100644
--- a/cern_caimira/tests/conftest.py
+++ b/cern_caimira/tests/conftest.py
@@ -90,6 +90,6 @@ def exposure_model_w_outside_temp_changes(data_registry, baseline_exposure_model
 def baseline_form_with_sr(baseline_form_data, data_registry):
     form_data_sr = baseline_form_data
     form_data_sr['short_range_option'] = 'short_range_yes'
-    form_data_sr['short_range_interactions'] = '[{"expiration": "Shouting", "start_time": "10:30", "duration": "30"}]'
+    form_data_sr['short_range_interactions'] = '{"group_1": [{"expiration": "Shouting", "start_time": "10:30", "duration": 30}]}'
     form_data_sr['short_range_occupants'] = 5
     return virus_validator.VirusFormData.from_dict(form_data_sr, data_registry)
diff --git a/cern_caimira/tests/test_report_generator.py b/cern_caimira/tests/test_report_generator.py
index f15833a2..43f36248 100644
--- a/cern_caimira/tests/test_report_generator.py
+++ b/cern_caimira/tests/test_report_generator.py
@@ -124,62 +124,3 @@ def test_expected_new_cases(baseline_form_with_sr: VirusFormData):
 
     lr_expected_new_cases = alternative_statistics['stats']['Base scenario without short-range interactions']['expected_new_cases']
     np.testing.assert_almost_equal(sr_lr_expected_new_cases, lr_expected_new_cases + sr_lr_prob_inf * baseline_form_with_sr.short_range_occupants, 2)
-
-
-def test_static_vs_dynamic_occupancy_from_form(baseline_form_data, data_registry):
-    """ 
-    Assert that the results between a static and dynamic occupancy model (from form inputs) are similar. 
-    """
-    executor_factory = partial(
-        concurrent.futures.ThreadPoolExecutor, 1,
-    )
-   
-    # By default the baseline form accepts static occupancy
-    static_occupancy_baseline_form: VirusFormData = VirusFormData.from_dict(baseline_form_data, data_registry)
-    static_occupancy_model = static_occupancy_baseline_form.build_model()
-    static_occupancy_report_data = rep_gen.calculate_report_data(static_occupancy_baseline_form, executor_factory)
-
-    # Update the initial form data to include dynamic occupancy (please note the 4 coffee and 1 lunch breaks)
-    baseline_form_data['occupancy_format'] = 'dynamic'
-    baseline_form_data['dynamic_infected_occupancy'] = json.dumps([
-        {'total_people': 1, 'start_time': '09:00', 'finish_time': '10:03'},
-        {'total_people': 0, 'start_time': '10:03', 'finish_time': '10:13'},
-        {'total_people': 1, 'start_time': '10:13', 'finish_time': '11:16'},
-        {'total_people': 0, 'start_time': '11:16', 'finish_time': '11:26'},
-        {'total_people': 1, 'start_time': '11:26', 'finish_time': '12:30'},
-        {'total_people': 0, 'start_time': '12:30', 'finish_time': '13:30'},
-        {'total_people': 1, 'start_time': '13:30', 'finish_time': '14:53'},
-        {'total_people': 0, 'start_time': '14:53', 'finish_time': '15:03'},
-        {'total_people': 1, 'start_time': '15:03', 'finish_time': '16:26'},
-        {'total_people': 0, 'start_time': '16:26', 'finish_time': '16:36'},
-        {'total_people': 1, 'start_time': '16:36', 'finish_time': '18:00'},
-    ])
-    baseline_form_data['dynamic_exposed_occupancy'] = json.dumps([
-        {'total_people': 9, 'start_time': '09:00', 'finish_time': '10:03'},
-        {'total_people': 0, 'start_time': '10:03', 'finish_time': '10:13'},
-        {'total_people': 9, 'start_time': '10:13', 'finish_time': '11:16'},
-        {'total_people': 0, 'start_time': '11:16', 'finish_time': '11:26'},
-        {'total_people': 9, 'start_time': '11:26', 'finish_time': '12:30'},
-        {'total_people': 0, 'start_time': '12:30', 'finish_time': '13:30'},
-        {'total_people': 9, 'start_time': '13:30', 'finish_time': '14:53'},
-        {'total_people': 0, 'start_time': '14:53', 'finish_time': '15:03'},
-        {'total_people': 9, 'start_time': '15:03', 'finish_time': '16:26'},
-        {'total_people': 0, 'start_time': '16:26', 'finish_time': '16:36'},
-        {'total_people': 9, 'start_time': '16:36', 'finish_time': '18:00'},
-    ])
-    baseline_form_data['total_people'] = 0
-    baseline_form_data['infected_people'] = 0
-
-    dynamic_occupancy_baseline_form: VirusFormData = VirusFormData.from_dict(baseline_form_data, data_registry)
-    dynamic_occupancy_model = dynamic_occupancy_baseline_form.build_model()
-    dynamic_occupancy_report_data = rep_gen.calculate_report_data(dynamic_occupancy_baseline_form, executor_factory)
-
-    assert (list(sorted(static_occupancy_model.concentration_model.infected.presence.transition_times())) == 
-            list(dynamic_occupancy_model.concentration_model.infected.number.transition_times))
-    assert (list(sorted(static_occupancy_model.exposed.presence.transition_times())) == 
-            list(dynamic_occupancy_model.exposed.number.transition_times))
-    
-    np.testing.assert_almost_equal(static_occupancy_report_data['prob_inf'], dynamic_occupancy_report_data['prob_inf'], 1)
-    assert dynamic_occupancy_report_data['expected_new_cases'] == None
-    assert dynamic_occupancy_report_data['prob_probabilistic_exposure'] == None
-    
\ No newline at end of file