diff --git a/cara/apps/calculator/static/form.html b/cara/apps/calculator/static/form.html
index b3944bc1..bd4c9df8 100644
--- a/cara/apps/calculator/static/form.html
+++ b/cara/apps/calculator/static/form.html
@@ -42,7 +42,7 @@ Beta v1.0.0 <span style="float:right; font-weight:bold">Please send feedback to
 
     <div id="DIVmechanical_ventilation" style="display:none">
         <input type="radio" id="air_type_supply" name="air_type" value="air_supply" onclick="require_fields(this)">
-        Air supply flow rate &nbsp;&nbsp; <input type="number" step=0.01 id="air_supply" name="air_supply" min="0"><br>
+        Air supply flow rate &nbsp;&nbsp; <input type="number" step=0.01 id="air_supply" name="air_supply" min="0" placeholder="(m³)"><br>
         <input type="radio" id="air_type_changes" name="air_type" value="air_changes" onclick="require_fields(this)">
         Air changes per hour &nbsp;&nbsp; <input type="number" step=0.01 id="air_changes" name="air_changes" min="0"><br>
     </div>
@@ -89,14 +89,14 @@ Beta v1.0.0 <span style="float:right; font-weight:bold">Please send feedback to
     Finish: <input type="time" id="infected_finish" name="infected_finish" value="18:00" required><br>
     <hr width="80%">
 
-    <span class="natural disabled">When is the event?</span><br>
-    <input type="radio" id="event_type_single" name="event_type" class="natural disabled" value="single_event" onclick="require_fields(this)" disabled></input>
-    <label for="event_type_single" class="natural disabled">Single event</label> &nbsp;&nbsp;
-    <label for="datepicker" class="natural disabled">Date: </label>
-    <input type="text" id="datepicker" class="natural disabled" name="single_event_date" disabled unrequired><br>
-    <input type="radio" id="event_type_recurrent" name="event_type" class="natural disabled" value="recurrent_event" onclick="require_fields(this)" disabled></input>
-    <label for="event_type_recurrent" class="natural disabled">Recurrent usage</label>
-    <select id="recurrent_event_month" name="recurrent_event_month" class="natural disabled" disabled>
+    When is the event?<br>
+    <input type="radio" id="event_type_single" name="event_type" value="single_event" onclick="require_fields(this)"></input>
+    <label for="event_type_single">Single event</label> &nbsp;&nbsp;
+    <label for="datepicker">Date: </label>
+    <input type="text" id="datepicker" name="single_event_date"><br>
+    <input type="radio" id="event_type_recurrent" name="event_type" value="recurrent_event" onclick="require_fields(this)"></input>
+    <label for="event_type_recurrent">Recurrent usage</label>
+    <select id="recurrent_event_month" name="recurrent_event_month">
         <option value="January">January</option>
         <option value="February">February</option>
         <option value="March">March</option>
diff --git a/cara/apps/calculator/static/js/form.js b/cara/apps/calculator/static/js/form.js
index 7e6cabed..d11f3ace 100644
--- a/cara/apps/calculator/static/js/form.js
+++ b/cara/apps/calculator/static/js/form.js
@@ -21,7 +21,6 @@ function show_hide(show, hide, obj) {
       show.style.display = "none";
       obj.checked = false;
       no_ventilation.checked = true;
-      unrequire_fields(obj);
   } else if (show.style.display === "none") {
       show.style.display = "block";
       hide.style.display = "none";
@@ -71,18 +70,6 @@ function require_fields(obj){
       break;
 } }
 
-function unrequire_fields(obj){
-  switch(obj.id) {
-    case "mechanical":
-      require_mechanical_ventilation(false);
-      break;
-    case "natural":
-      require_natural_ventilation(false);
-      break;
-    default:
-      break;
-} }
-
 function require_room_volume(option) {
     $("#room_volume").prop('required',option);
 }
@@ -106,21 +93,7 @@ function require_natural_ventilation(option) {
     $("#interval").prop('required',option);
     $("#event_type_single").prop('required',option);
     $("#event_type_recurrent").prop('required',option);
-
-    document.getElementById("event_type_single").disabled = !option;
-    document.getElementById("event_type_recurrent").disabled = !option;
-
-    if (option) {
-      var elements = document.getElementsByClassName("natural disabled");
-      for(var i = elements.length - 1; i >= 0; --i)
-          elements[i].className = "natural enabled";
-    }
-    else {
-      $(".natural disabled").disabled = true
-      var elements = document.getElementsByClassName("natural enabled");
-      for(var i = elements.length - 1; i >= 0; --i)
-          elements[i].className = "natural disabled";
-} }
+}
 
 function require_air_changes(option) {
     $("#air_changes").prop('required',option);