exhalation

If a full face mask doesn’t fit well, forming a tight seal around the nose and mouth with exit vents for exhalation, you risk breathing potentially dangerous levels of CO2 back into the mask, which you could then inhale with your next breath.

Some restaurants are experimenting with tabletop filters that can suck in diners’ exhalations and send the filtered air skyward instead of toward a dining companion’s face.

If CO2 levels reach above 700 parts per million, that means people’s exhalation is filling up the room.

Numerous experts — epidemiologists, virologists and engineers — supported the notion of using exhalation as a conservative proxy to show potential transmission risk in various settings.