Control humidity in Aircraft Hangar

This is a case that I think about often, it was originally posted in our old Google Group, but I wanted to “rescue” it and bring it to the new community as I think it can be helpful for other people.

Humid air in Florida: analysing the problem!

Jules in Florida explained that he had an aircraft hangar that suffered from condensation and mold. They installed an exhaust fan to aid in ventilation. But due to the location, it can happen that the humidity outside can be greater than the one inside. And if that’s the case, you don’t want to bring extra-humid air inside!

So the logic in this case is:

  • If “Hangar Humidity” more than 60%
  • AND “Outside Humidity” less than 60%
  • THEN “Fan Switch” ON
  • else “Fan Switch” OFF

How are we going to measure these things?

Jules originally used the following devices:

  1. Inside humidity monitored by an Aeon Labs multisensor.
  2. Outside humidity monitored by AccuWeather Connect SmartApp
  3. Fan switched by GE Z-Wave switch

They can all be controlled through Smart things, which is controllable through IFTTT, so we know we could trigger things in IFTTT when we were over the threshold for humidity.

You could achieve a similar result with any two humidity sensors and a switch or plug that work with Tuya, or IFTTT, or via webhooks, the logic is all the same.

Working out the variables and conditions in Apilio


  • Create two Boolean variables in Apilio, one called “humidity_inside_above_60” and the other called “humidity_outside_above_60”
  • For each of those two variables, you need two IFTTT Applets (so 4 in total), to set it to false or true:
    • If humidity above 60, set Boolean variable to true
    • If humidity below 59, set Boolean variable to false


  • Create two conditions
    • inside_conditions_good_for_venting
      • connected to the variable “humidity_inside_above_60”
      • required state: true
      • (this conditions will return true if inside humidity is above 60)
    • outside_conditions_good_for_venting
      • connected to the variable “humidity_outside_above_60”
      • required state: false
      • (this condition will return true if outside humidity is below 60)


  • Connect it to the two conditions
  • If positive, switch fan on (via an IFTTT action Apilio, set an event name that you will use in an applet to turn the fan on via IFTTT)
  • If negative, switch fan off (via an IFTTT action in Apilio, to turn it off via IFTTT)


I think this is a fantastic example of quite a simple implementation with two sensors and a switch, but that needs that Apilio comparison to make it work in the conditions. Here’s the original post.

Let me know if you have any questions or if this was helpful as an idea! :smiley: