Is it possible to create a logic that detects a rapid rise in humidity? I have a “Aeotek Multisensor 6” which is mounted in the bathroom. I want it to detect that someone is showering or bathing, but the challenge is that the lower humidity value varies. Now it is winter in Norway and we often have low humidity, in summer it is higher. However, it can vary, depending on, among other things, the outdoor temperature. This makes it difficult to set a cut-off value for when you want a flow to be triggered. In addition, the sensor is located 2-3 meters from the bath and shower due to access to electricity, thus it takes a little longer before the humidity increases significantly. Therefore, I prefer it to respond to a rapid increase in humidity instead of just a static value. Is it possible to make a logic via e.g. “Better Logic”?
You can place another humidity sensor outside the bathroom, so you can calculate the difference between the ambient humidity and the bathroom humidity.
I have made following logic to control the shower ventilation
Make the ventilation higher if:
- Shower relative humidity is over 65% and
- Shower absolute humidity is higher than outdoor absolute humidity and
- Shower relative humidity is 13% higher than average indoor relative humidity****
or
- Shower relative humidity is over 65% and
- Average indoor absolute humidity is higher than outdoor absolute humidity
Make the ventilation lower if:
- Shower relative humidity is less than 55%
or
- Outdoor absolute humidity is higher than shower absolute humidity
or
- Shower relative humidity + 10% is higher than average indoor relative humidity
It works, but maybe, just maybe I have overdone it. 
A bit late, but maybe the app Insight Trends comes in handy.
It can detect how fast or how slow a sensors’ value changes over time.
Hi did you find a good way to control this?
Like Jan wrote, you can use an other humidity sensor to compare the values with.
I chose to use the same humidity sensor.
Flow1
When I enter the bathroom, the current humidity value is saved to a predefined variable.
Flow2
When the hot shower is running, compare the change in humidity, and if it is X % higher than the saved value, fire the action cards. For me, using an increase of 6% works fine.
sounds good i will try it 
