Hi. I’m new to Home Assistant and yet planning my first attempt to automate something. I have a mechanical ventilation system at home that basically sucks the inside air from the toilets and kitchen, an Echo device, and 4 Shelly relay switchs that some friends gave me as a present to ensure I didn’t lose the opportunity to get into the automation world.
I’m planning the following - please let me know it that’s crazy and should start with something simpler or should give it a try 
- Plug a Shelly relay into the mechanical ventilation system.
- Install few window sensors on the windows oposite to the mechanical ventilation extraction grids, to ensure the ventilation flows through the rooms. The ventilation should have had installed the external air grids but for some reason the builders got rid of them, so I depend on the windows being open.
- Install 2 air quality monitor (the house has 2 floors).
Setup the system as follows:
- If any of the air quality monitors CO2, VOC and/or humidity levels are above a certain threshold:
- AND Required windows are open:
- Trigger the mechanical ventilation system.
- AND Required windows are closed:
- Send a message through the Echo every few minutes to alert that the windows should be open.
- AND Required windows are open:
Excuse me if I’m talking non-sense, as I just discovered Home Assistant and I’m just trying to build my first setup. I’ve anyone has done something similar and can recommend sensors, I’m glad to learn from others experiences.