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HoobieHoo t1_itjo3r2 wrote

Glasses fogging isn’t reliable as even N95 masks allow water vapour to pass. With the huff test, a well sealed mask will collapse and expand slightly as you inhale and exhale, respectively. If it doesn’t do that, then it isn’t sealed properly.

Regular surgical masks aren’t designed to fit with a seal like N95s are.


randxalthor t1_itkbtj4 wrote

You seem to have ignored my comment about how surgical masks aren't designed to seal.

Also, the fog test for N95s was the quick and dirty solution. It does, in fact, work, though it's not a good substitute for the aspartame test, as I pointed out. If your nose bridge fits properly and your straps are properly placed over your head, breathing out will not create enough positive pressure to push the mask away from your skin. The nose bridge is also the most critical part of the mask for fit because of the tight curvature, which is why it's a decent rule of thumb.

The water vapor you breathe out with a good seal will thus be forced to travel more evenly through the mask and not concentrate on your glasses. Many medical professionals wear glasses with N95s without worrying about fogging precisely because their masks fit well around the nose.

And in case you're wondering why I know all this, it's because I worked before and during the pandemic in bioweapons defense designing vapor and aerosol filters, and my SO worked as one of the aforementioned medical professionals treating COVID-positive patients.