I wrote about issues with N95 respirators with exhalation valves the other day, and decided to do a quick demonstration of the concerns.

Exhalation valves on some N95 masks are designed to make it easier to breathe out, because these one-way valves release exhaled air without forcing it through a filter.

• The mask still protects the wearer from breathing things in, but it does very little to prevent an infected person from spreading infectious droplets when they breathe out.
• That’s a big problem when the mask is meant to protect others FROM the wearer, which is why masks are recommended outside of specific healthcare situations in the first place.
• In particular, cloth masks are becoming widely used in these situations, as they’re meant to protect others. They reduce the risk by containing the wearer’s respiratory droplets within the mask.

However, I’ve seen ads for cloth masks with valves (see picture right). That’s a bit like someone marketing an umbrella that is less likely to get caught by the wind because they’ve cut big holes in it.

To make the concept a bit more visual, take a look at the picture below. I put on a cloth mask, a surgical mask, an N95 mask and N95 mask with an exhalation valve. I then held a culture plate in front of my face and exhaled forcefully and coughed. As you can see, there was no bacterial growth, except from the mask with a valve (where there was a lot).

So, unless you are using an N95 mask during a high risk healthcare procedure (where the only concern is what you’re inhaling, and not what you’re exhaling), don’t use a mask with a valve.