There is still lots of confusion about what use of different types of masks is supposed to do in different situations. As I’ve said before, it comes down to thinking about who the mask is meant to protect – the user, or people around the user. This dictates what type of mask should be used.
- These masks protect others from the user’s respiratory droplets – the little liquid particles that we expel when talking, breathing, coughing or doing similar things. Exposure to such droplets is the biggest risk for transmission of SARS-CoV-2. Cloth masks help contain droplets. While they will help protect the user to some degree, they are mainly to protect others FROM the user.
- These are meant to protect others FROM the person wearing the mask (same as cloth masks).
- These masks can help protect both the user and those around the user. IF they are properly fitted to create a seal around the mouth and nose (unfortunately many people don’t realize these masks need to be fit-tested to be effective), then they will help protect the user. However, the user also needs to protect the eyes – it makes little sense to cover some mucous membranes on your face (nose and mouth) and leave two others just above those wide open and unshielded.
- N95 respirators can also protect others FROM the wearer, since they are good filtering masks, IF they don’t have an exhalation valve.
What is an exhalation valve?
An exhalation valve makes it easier to breathe by allowing air to leave the mask without passing through a filter. That’s fine if the mask is being worn to protect the user, who inhales filtered air and is presumably not exhaling infectious droplets. However, if the person is infected and there is virus in the expelled air, an N95 with an exhalation valve will not protect others FROM the user. Since most community mask usage is designed to protect others from people expelling infectious droplets, in situations where mask use by everyone is mandated to reduce the risk of exposing others, N95 masks with exhalation valves should not be used.