Hello
I work in the research arena. We use paprs which have hepatitis filtered cartridges. Charcoal isn't used as much. Also there are a variety of filter types depended on the gas or organism you want to have protection from. Certainly an old charcoal filter wouldn't protect you against SARS for example. It may protect you from a gas like riot control cs gas. But new ways are made every several years to protect you. When I see people run out and buy old world war 2 masks I sticker to myself. The fools.