This is also very true for the air filters on your home furnace/heat pump, if you have one. Even if you aren’t running the heat, if you are running the furnace/heat pump’s fan to circulate air periodically (which you should be doing to avoid stagnation), air is still passing through the filter. I live in the Seattle area, and our furnace filter comes out absolutely filthy black after every bout of wildfire smoke. It nasty.
This is also very true for the air filters on your home furnace/heat pump, if you have one. Even if you aren’t running the heat, if you are running the furnace/heat pump’s fan to circulate air periodically (which you should be doing to avoid stagnation), air is still passing through the filter. I live in the Seattle area, and our furnace filter comes out absolutely filthy black after every bout of wildfire smoke. It nasty.