Our pantry foam is stapled onto the metal grille over the pantry.
We bought more of the Duck brand foam filter in the AC section of WM. Since the foam gets dirty so fast, it seems to be the best option for dust collection. They are easy to wash and reuse. Unlike the paper filters in residential vents. I usually wash mine every 3-4 wks in summer.
I cut a new set so can switch, wash the dirty and let it dry. So the vents are never without foam filters.
Besides foam -3M Filtrete can be cut to fit and is available at Amazon:
http://www.amazon.com/s?ie=UTF8&page...ter%20Material