You can see the fit-testing on youtube. It’s pretty involved and not something you can do at home—they put a hood over your head and spray in a bunch of super-sweet aerosol, and if you can taste it through the mask then the fit isn’t good enough.
On the other hand, they do that once a year, just to make sure that model is capable of fitting your face shape. The masks are supposed to be one-size-fits most. On a daily basis, the fit procedure is to put it on and blow out and see if you can feel any air escaping around your nose. This seems very achievable and likely to give a decent fit for most people.
You can see the fit-testing on youtube. It’s pretty involved and not something you can do at home—they put a hood over your head and spray in a bunch of super-sweet aerosol, and if you can taste it through the mask then the fit isn’t good enough.
On the other hand, they do that once a year, just to make sure that model is capable of fitting your face shape. The masks are supposed to be one-size-fits most. On a daily basis, the fit procedure is to put it on and blow out and see if you can feel any air escaping around your nose. This seems very achievable and likely to give a decent fit for most people.