Well, you could suggest people perfume their masks. Maybe dried peels of orange, lemon, some cloves perhaps, a little basil and rosemary. Like a pomander, what the plague doctor's used to wear. Was all the rage back in the day, you know - get a priest to read some galders or spells over it for good measure too.

Worst case, they get zero protection but you don't have to smell their halitosis.