Masks for fires and earthquakes aren't necessarily good for pandemics

I haven't posted an article in a while because I've been spending a lot of time handling various impacts of COVID-19 on my "day job" research, but I wanted to surface briefly to mention an important point.  Many people have face masks in their emergency kits in case they need to deal with rubble and dust after a quake.  In places like California that have had major wildfires recently, even many people who don't prepare for quakes have N95 respirators left over from those smoke episodes, and many of those masks have a "cool valve" one-way vent that opens outward and makes breathing more comfortable.

It's important to realize that these masks protect the wearer from outside hazards (including germs from other people), but do not protect other people from the wearer.

Click image to get full sized version suitable for sharing

This is crucial because the point of wearing face coverings in public, which is becoming common guidance around the world, is not so much to protect you (they don't do a great job of that) but more to protect other people from you if you are infected but don't know it, and are producing large respiratory droplets full of virus.  Many people who have the virus don't have any symptoms and don't realize they have it, but can still be contagious, and this is now being estimated to account for a huge amount of community spread.

If you are exhaling virus, and you wear a mask with a one-way vent, then you are exhaling that virus unimpeded at anyone else who is nearby, and most of the point of wearing the mask is wasted.

(This is not a concern if a healthcare worker is wearing a mask to protect them from an infectious patient; then it's appropriate.)

So please, even if you feel fine and are wearing a mask out in public (and especially if you are wearing a mask because you are sick and want to prevent exposing other people in the home), do not use masks with one-way valves!  Please share the graphic that I put together.  Better to spread the word, than to spread the virus.


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