diff --git a/cara/apps/calculator/model_generator.py b/cara/apps/calculator/model_generator.py
index efef71a9..4986d2dc 100644
--- a/cara/apps/calculator/model_generator.py
+++ b/cara/apps/calculator/model_generator.py
@@ -3,6 +3,7 @@ from dataclasses import dataclass
 import typing
 
 from cara import models
+from typing import List, Tuple
 
 
 @dataclass
@@ -12,6 +13,8 @@ class FormData:
     activity_finish: int
     lunch_start: int
     lunch_finish: int
+    infected_start: int
+    infected_finish: int
 
     activity_type: str
     air_changes: float
@@ -40,6 +43,7 @@ class FormData:
     window_width: float
     windows_number: int
     windows_open: str
+    coffee_times: List[Tuple[int, int]]
 
     @classmethod
     def from_dict(cls, form_data: typing.Dict) -> "FormData":
@@ -90,7 +94,10 @@ class FormData:
             window_height=float(form_data['window_height']),
             window_width=float(form_data['window_width']),
             windows_number=int(form_data['windows_number']),
-            windows_open=form_data['windows_open']
+            windows_open=form_data['windows_open'],
+            infected_start=time_string_to_minutes(form_data['infected_start']),
+            infected_finish=time_string_to_minutes(form_data['infected_finish']),
+            coffee_times=[]
         )
 
     # TODO: Remove the tmp_raw_form_data usage.
@@ -142,8 +149,11 @@ class FormData:
         leave_times = [self.lunch_start]
         enter_times = [self.lunch_finish]
         for minute in range(self.activity_start, self.activity_finish, coffee_period):
-            leave_times.append(minute + coffee_period // 2)
-            enter_times.append(minute + coffee_period // 2 + self.coffee_duration)
+            start = minute + coffee_period // 2
+            end = start + self.coffee_duration
+            self.coffee_times.append((start, end))
+            leave_times.append(start)
+            enter_times.append(end)
 
         # These lists represent the times where the infected person leaves or enters the room, respectively, sorted in
         # reverse order. Note that these lists allows the person to "leave" when they should not even be present in the
@@ -154,20 +164,20 @@ class FormData:
         # This loop iterates through the lists above, populating present_intervals with (enter, leave) intervals
         # representing the infected person entering and leaving the room. Note that if one of the evenly spaced coffee-
         # breaks happens to coincide with the lunch-break, it is simply ignored.
-        is_present = True
         present_intervals = []
-        time = self.activity_start
-        while time < self.activity_finish:
+        time = self.infected_start
+        is_present = True
+        while time < self.infected_finish:
             if is_present:
                 if not leave_times:
-                    present_intervals.append((time / 60, self.activity_finish / 60))
+                    present_intervals.append((time / 60, self.infected_finish / 60))
                     break
 
-                if leave_times[-1] < time:
+                if leave_times[-1] <= time:
                     leave_times.pop()
                 else:
                     new_time = leave_times.pop()
-                    present_intervals.append((time / 60, min(new_time, self.activity_finish) / 60))
+                    present_intervals.append((time / 60, min(new_time, self.infected_finish) / 60))
                     is_present = False
                     time = new_time
 
@@ -250,12 +260,14 @@ def baseline_raw_form_data():
         'air_changes': '',
         'air_supply': '',
         'ceiling_height': '',
-        'coffee_breaks': '5',
+        'coffee_breaks': '2',
         'coffee_duration': '10',
         'coffee_option': '1',
         'event_type': 'single_event',
         'floor_area': '',
         'hepa_option': '0',
+        'infected_finish': '15:00',
+        'infected_start': '10:00',
         'infected_people': '1',
         'lunch_finish': '13:30',
         'lunch_option': '1',
diff --git a/cara/tests/apps/calculator/test_model_generator.py b/cara/tests/apps/calculator/test_model_generator.py
index 040ed5df..48ec0c13 100644
--- a/cara/tests/apps/calculator/test_model_generator.py
+++ b/cara/tests/apps/calculator/test_model_generator.py
@@ -85,14 +85,14 @@ def test_ventilation_window_hepa(baseline_form):
     ventilation = models.MultipleVentilation((window,hepa))
 
     baseline_form.ventilation_type = 'natural'
-    baseline_form.windows_open = '10 min / 2h'
+    baseline_form.windows_open = 'interval'
     baseline_form.event_type = 'recurrent_event'
     baseline_form.recurrent_event_month = 'December'
     baseline_form.window_height = 1.6
     baseline_form.opening_distance = 0.6
     baseline_form.hepa_option = True
 
-    ts = np.linspace(8, 16, 100)
+    ts = np.linspace(9, 17, 100)
     np.testing.assert_allclose([ventilation.air_exchange(room, t) for t in ts],
                                [baseline_form.ventilation().air_exchange(room, t) for t in ts])
 
@@ -100,12 +100,14 @@ def test_ventilation_window_hepa(baseline_form):
 def test_present_intervals(baseline_form):
     baseline_form.coffee_duration = 15
     baseline_form.coffee_option = True
-    baseline_form.coffee_breaks = 4
+    baseline_form.coffee_breaks = 2
     baseline_form.activity_start = 9 * 60
     baseline_form.activity_finish = 17 * 60
     baseline_form.lunch_start = 12 * 60 + 30
     baseline_form.lunch_finish = 13 * 60 + 30
-    correct = ((9, 10), (10.25, 12), (12.25, 12.5), (13.5, 14), (14.25, 16), (16.25, 17))
+    baseline_form.infected_start = 10 * 60
+    baseline_form.infected_finish = 15 * 60
+    correct = ((10, 11), (11.25, 12.5), (13.5, 15))
     assert baseline_form.present_interval().present_times == correct