diff --git a/caimira/apps/calculator/co2_model_generator.py b/caimira/apps/calculator/co2_model_generator.py
index 3aa13118..f0341338 100644
--- a/caimira/apps/calculator/co2_model_generator.py
+++ b/caimira/apps/calculator/co2_model_generator.py
@@ -315,7 +315,7 @@ class CO2FormData:
         )
 
     def ventilation_transition_times(self, last_present_time) -> typing.Tuple[float, ...]:
-        if self.ventilation_type == 'natural_ventilation' and self.window_opening_regime == 'windows_open_periodically':
+        if self.ventilation_type == 'from_fitting' and self.window_opening_regime == 'windows_open_periodically':
             transition_times = sorted(models.PeriodicInterval(self.windows_frequency, 
                     self.windows_duration, min(self.infected_start, self.exposed_start)/60).transition_times())
             return tuple(filter(lambda x: x < last_present_time, transition_times))
diff --git a/caimira/apps/calculator/model_generator.py b/caimira/apps/calculator/model_generator.py
index 7ccf8395..58ddc8e8 100644
--- a/caimira/apps/calculator/model_generator.py
+++ b/caimira/apps/calculator/model_generator.py
@@ -439,10 +439,24 @@ class FormData:
 
     def ventilation(self) -> models._VentilationBase:
         always_on = models.PeriodicInterval(period=120, duration=120)
+        periodic_interval = models.PeriodicInterval(self.windows_frequency, self.windows_duration, min(self.infected_start, self.exposed_start)/60)
+
+        if self.CO2_data_option:
+            ventilations = []   
+            if self.ventilation_type == 'from_fitting' and self.window_opening_regime == 'windows_open_periodically':                
+                for index, time in enumerate(sorted(list(periodic_interval.transition_times()))[:-1]):
+                    if index < len(self.CO2_fitting_result['ventilation_values']):
+                        ventilations.append(models.AirChange(active=models.SpecificInterval(present_times=((time, time + self.windows_duration/60), )), 
+                                                             air_exch=self.CO2_fitting_result['ventilation_values'][index]))
+                    else: break
+            else:
+                ventilations.append(models.AirChange(active=always_on, air_exch=self.CO2_fitting_result['ventilation_values'][0]))
+            return models.MultipleVentilation(tuple(ventilations))
+
         # Initializes a ventilation instance as a window if 'natural_ventilation' is selected, or as a HEPA-filter otherwise
         if self.ventilation_type == 'natural_ventilation':
             if self.window_opening_regime == 'windows_open_periodically':
-                window_interval = models.PeriodicInterval(self.windows_frequency, self.windows_duration, min(self.infected_start, self.exposed_start)/60)
+                window_interval = periodic_interval
             else:
                 window_interval = always_on
 
diff --git a/caimira/apps/calculator/static/js/form.js b/caimira/apps/calculator/static/js/form.js
index 63ac8673..02c2408a 100644
--- a/caimira/apps/calculator/static/js/form.js
+++ b/caimira/apps/calculator/static/js/form.js
@@ -244,6 +244,9 @@ function removeInvalid(id) {
 }
 
 function on_ventilation_type_change() {
+  if ($('input[type=radio][id=from_fitting').is(':checked')) $('#DIVfrom_fitting').after($('#window_opening_regime'));
+  else $('#DIVopening_distance').after($('#window_opening_regime'));
+
   ventilation_types = $('input[type=radio][name=ventilation_type]');
   ventilation_types.each(function (index) {
     if (this.checked) {
@@ -494,25 +497,12 @@ function on_coffee_break_option_change() {
 }
 
 function ventilation_from_fitting(condition) {
-  let CO2_data_options = $('input[type=radio][name=ventilation_type]');
-  let hepa_options = $('input[type=radio][name=hepa_option]');
   if (condition) {
-    $('input[type=radio][id=no_ventilation]').click();
-    CO2_data_options.each(function (index){
-      $(this).prop("disabled", true);
-    });
-    hepa_options.each(function (index){
-      $(this).prop("disabled", true);
-    });
-    $('#DIVhepa_amount').after($('#window_opening_regime'));
+    $('input[type=radio][id=from_fitting]').click();
+    $('#DIVfrom_fitting').after($('#window_opening_regime'));
   }
   else {
-    CO2_data_options.each(function (index){
-      $(this).prop("disabled", false);
-    });
-    hepa_options.each(function (index){
-      $(this).prop("disabled", false);
-    });
+    $('input[type=radio][id=no_ventilation]').click();
     $('#DIVopening_distance').after($('#window_opening_regime'));
   }
 }
diff --git a/caimira/apps/templates/base/calculator.form.html.j2 b/caimira/apps/templates/base/calculator.form.html.j2
index 47d3368c..7561d4a6 100644
--- a/caimira/apps/templates/base/calculator.form.html.j2
+++ b/caimira/apps/templates/base/calculator.form.html.j2
@@ -197,16 +197,18 @@
       <div class='sub_title'>Ventilation type:</div>
       
       <div class="split">
-      <div>
-      <input type="radio" id="no_ventilation" name="ventilation_type" value="no_ventilation" checked>
-        <label for="no_ventilation">No ventilation</label>
-      <input class="ml-2" type="radio" id="mechanical_ventilation" name="ventilation_type" value="mechanical_ventilation" data-enables="#DIVmechanical_ventilation">
-        <label for="mechanical_ventilation">Mechanical</label>
-      </div>
-      <div>
-      <input type="radio" id="natural_ventilation" name="ventilation_type" value="natural_ventilation" data-enables="#DIVnatural_ventilation" data-toggle="modal" data-target="#warning_modal">
-        <label for="natural_ventilation">Natural</label><br>
-      </div>
+        <div>
+        <input type="radio" id="no_ventilation" name="ventilation_type" value="no_ventilation" checked>
+          <label for="no_ventilation">No ventilation</label>
+        <input class="ml-2" type="radio" id="mechanical_ventilation" name="ventilation_type" value="mechanical_ventilation" data-enables="#DIVmechanical_ventilation">
+          <label for="mechanical_ventilation">Mechanical</label>
+        </div>
+        <div>
+        <input type="radio" id="natural_ventilation" name="ventilation_type" value="natural_ventilation" data-enables="#DIVnatural_ventilation" data-toggle="modal" data-target="#warning_modal">
+          <label for="natural_ventilation">Natural</label>
+        <input class="ml-2" type="radio" id="from_fitting" name="ventilation_type" value="from_fitting" data-enables="#DIVfrom_fitting">
+          <label for="from_fitting">Fitting</label>
+        </div>
       </div>
 
       <!-- Modal -->
@@ -296,6 +298,9 @@
             </div>
           </div>
 
+      </div>
+      <br/>
+      <div id="DIVfrom_fitting" style="display:none">
       </div>
       <br/>
       <div class='sub_title'>HEPA filtration:</div>