That is a very convoluted way to show that your beard should not cross the seal.<p>If you want to get the message across, diagrams like this are not very helpful. It leads to people checking for which part of it might apply to them without making them aware of the underlying reason for it.
I have a short full beard but seem to be able to form a seal. If I follow the directions for checking the seal — blocking the intake and breathing in, checking for the mask to collapse in, then blocking the outlet and checking for it to balloon out — it works. So do I have a seal or not?
Looks like this has been around a while.
<a href="https://blogs.cdc.gov/niosh-science-blog/2017/11/02/noshave/" rel="nofollow">https://blogs.cdc.gov/niosh-science-blog/2017/11/02/noshave/</a>
Every firefighter knows this. Which is why you never see firefighters with beards. (Or sometimes you do but we'll also be shaving on the way to the fire while the truck is bouncing down the road. Some lessons are learned the hard way.)