[semi-extrinsic]

I don't understand why anyone would DIY an air filter, when you can get e.g. a pair of 3M 6092x cartridges for $20.

[Scene_Cast2]

As comfortable as 3M half-face respirators are, having people in the room wear a mask until vapors subside is a hassle - especially if the room is in the basement or a northern climate where opening a window isn't possible or desirable.