Does the air flow (and thus the air filter) for forced hot air furnace go in the same direction for heat & air
I know that the arrow on the filter must face the same way as the air flow, but don't know if the air flows into furnace or out of furnace at the point where the filter is placed. Also think maybe it is different when I run the air than when I run the
You can test it easily enough. Turn on the system, then hold a paper napkin or something similar in the opening where the filter goes. see which way the airflow pulls the paper.



