Nest Thermostat "when fan turns on/off" flow

Is it possible to create a flow for a Nest Thermostat to turn on a device “when fan turns on” and off again “when fan turns off”? I am researching scent diffusers and only want them to dispense when the fan in my HVAC system is running. Thank you

It think so.
When I got it right, something like this:

When…


And…

(mode = hvac?)
Then…
turn on fan Y
Else…
turn off fan Y

An alternative trigger could be something like:
When…
every X minutes

Hi Peter, Thank you for your response. The problem is, the modes do not include “fan”. Normally, the temperature setting and mode would stay consistent. In A/C mode, the compressor would kick in and the fan would then turn on until the desired temperature is reached and turn off again. The diffuser would continue to run without the fan dispersing the scent. Therefore wasting the scent oil. I currently use a diffuser that is connected to a HVAC air switch connected to a forced air duct which turns the diffuser on and off as needed. The problem is, that is a very expensive diffuser and I want to install a much smaller and less expensive unit that does not have that capability in my vacation home. The geek in me of course thinks this should be an easy option but of course, I’ve already spent more time trying to figure it out than it will ever be worth…

YW!
I guess you’d request Athom for a flowcard / extra mode detection for the ‘fan’ mode.
Unfortunately ‘official’ Athom apps can be very basic.

For example, this is available with the tadoZones community app:
‘When’ cards:

‘And’ card: