I think it was 160F or 170 F for 20 min (be careful not to melt or char the elastic in the straps of the masks)
Hmmm. I’ve been running 165F for 20 minutes (basically because that’s the lowest temp I can reliably get my toaster oven to maintain. It is supposed to be able to do 150 deg. F, but I have not figured out how, yet.) It is a big oven and runs the elements at a low power when low (not just adjusting the timing of full on / off cycles, so adverse radiative heat effects seem low.
165 deg. F causes no visible damage, to my eyes, anyway, but I suppose it could affect the media on a microscopic scale, or perhaps decrease its electrostatic action?
That decrease in efficiency is still concerning, as I only have 5 masks (2 at Mom’s and 3 @ home) but, OTOH, I highly doubt I’ll run into high levels of aerosols at the grocery store.