My company (Amaris Company) has been using motion detectors in the garage to turn on the exhaust fan.
- The exhaust fan runs anytime there is motion in the garage, which I think might be the best idea.
- It will run when a car is moving in or out of the garage or if you are simply walking around in the garage.
This might mean you run the fan more often, but I believe it might add extra protection for home occupants and at the end of the day, that is why we are putting exhaust fans in the garage.
For more information:
Read Jesse Terzi's Q&A "How can we prevent car fumes from polluting our house through the attached garage?"