Where to put this? HVAC? Environmental? OMG! IT'S MOLDY!

[Jerry Peck]

Oh Great! NOW WHAT?

https://buildingscience.com/documents/building-science-insights/bsi-109-how-changing-filters-led-condensation-and-mold-problem?

[Gunnar Alquist]

I sure am glad that I live in California where all we have to worry about is earthquakes and extreme wildfires. None of this scary mold stuff.

BTW, as far as I know, HVAC contractors are still putting filters in return air grilles out here.