Exhaust Ventilation Sucks Wildfire Smoke Right into a House. Not Good.
Exhaust Ventilation is extremely common in in almost all states including California. Operation of an exhaust ventilation system decreases the air pressure inside a home’s breathing zone, where people live. As a result indoor air pressure becomes less than outdoor air pressure which sucks smokey outdoor air into the breathing zone through any openings that may exist in the home’s exterior. That is why experts advise against use of ventilation systems (exhaust systems) during periods of wildfire smoke.