diff --git a/app/covid-calculator.ipynb b/app/covid-calculator.ipynb
index 15f4517d..c6ede9cf 100644
--- a/app/covid-calculator.ipynb
+++ b/app/covid-calculator.ipynb
@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -11,58 +11,30 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 42,
+   "execution_count": 15,
    "metadata": {
     "pycharm": {
      "name": "#%%\n"
     }
    },
-   "outputs": [
-    {
-     "data": {
-      "text/plain": "VBox(children=(HTML(value='<font size=\"+2\"><b>CARA</b> Covid Calculator</font>'), Text(value='', description='…",
-      "application/vnd.jupyter.widget-view+json": {
-       "version_major": 2,
-       "version_minor": 0,
-       "model_id": "cb4016cbd61a455780fd5b7d9b8585db"
-      }
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "outputs": [],
    "source": [
-    "intro = w.VBox(children=(w.HTML(value='<font size=\"+2\"><b>CARA</b> Covid Calculator</font>'),\n",
+    "intro_box = w.VBox(children=(w.HTML(value='<font size=\"+2\"><b>CARA</b> Covid Calculator</font>'),\n",
     "                         w.Text(placeholder=\"E.g. Workshop without masks\", description=\"Simulation name:\",\n",
     "                                style={'description_width': '35%'}),\n",
     "                         w.Text(placeholder=\"E.g. 17/R-033\", description=\"Room number:\",\n",
-    "                                style={'description_width': '35%'})))\n",
-    "\n",
-    "intro"
+    "                                style={'description_width': '35%'})))"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": 16,
    "metadata": {
     "pycharm": {
      "name": "#%%\n"
     }
    },
-   "outputs": [
-    {
-     "data": {
-      "text/plain": "VBox(children=(Text(value='', description='Room volume', placeholder='Room volume (m³)', style=DescriptionStyl…",
-      "application/vnd.jupyter.widget-view+json": {
-       "version_major": 2,
-       "version_minor": 0,
-       "model_id": "152f11e8cd014cd5847392b559a4424b"
-      }
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "outputs": [],
    "source": [
     "volume_text = w.Text(placeholder=\"Room volume (m³)\", description=\"Room volume\")\n",
     "area_text = w.Text(placeholder=\"Room floor area (m²)\", description=\"Floor area\")\n",
@@ -70,20 +42,64 @@
     "\n",
     "room_dimensions_box = w.VBox(children=(volume_text, w.Label(value=\"------- OR -------\"),area_text, height_text),\n",
     "                             layout=w.Layout(align_items='center'))\n",
-    "def manage_text_fields(b):\n",
+    "def manage_room_text_fields(_):\n",
     "    volume_text.disabled = bool(area_text.value) or bool(height_text.value)\n",
     "    area_text.disabled = bool(volume_text.value)\n",
     "    height_text.disabled = bool(volume_text.value)\n",
     "\n",
     "for text in [volume_text, area_text, height_text]:\n",
-    "    text.observe(manage_text_fields)\n",
+    "    text.observe(manage_room_text_fields)\n",
     "    text.style.description_width = \"50%\"\n",
     "\n",
-    "volume_text.observe(manage_text_fields)\n",
-    "area_text.observe(manage_text_fields)\n",
-    "height_text.observe(manage_text_fields)\n",
+    "volume_text.observe(manage_room_text_fields)\n",
+    "area_text.observe(manage_room_text_fields)\n",
+    "height_text.observe(manage_room_text_fields)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 22,
+   "metadata": {
+    "pycharm": {
+     "name": "#%%\n"
+    }
+   },
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "a33e789cd87f4cff829c098073adcb4e",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(ToggleButton(value=False, description='Mechanical ventilation', layout=Layout(width='100%')), T…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "mechanical_button = w.ToggleButton(value=False, description='Mechanical ventilation', layout={'width': '100%'})\n",
+    "acph_text = w.Text(description=\"Air changes per hour\", style={'description_width': 'aut'})\n",
+    "asfr_text = w.Text(description=\"Air supply flow rate\", style={'description_width': '45%'})\n",
     "\n",
-    "room_dimensions_box"
+    "def toggle_mechanical(b: w.Button):\n",
+    "    acph_text.disabled = not (mechanical_button.value or asfr_text.value)\n",
+    "    asfr_text.disabled = not (mechanical_button.value or acph_text.value)\n",
+    "\n",
+    "w.jsdlink((acph_text, 'value'), (asfr_text, 'disabled'))\n",
+    "w.jsdlink((asfr_text, 'value'), (acph_text, 'disabled'))\n",
+    "acph_text.disabled = True\n",
+    "asfr_text.disabled = True\n",
+    "\n",
+    "mechanical_button.observe(toggle_mechanical)\n",
+    "\n",
+    "mech_vent_box = w.VBox(\n",
+    "    children=(mechanical_button, acph_text, w.Label(value=\"------- OR -------\"), asfr_text),\n",
+    "    layout=w.Layout(align_items='center')\n",
+    ")"
    ]
   }
  ],