Excellent advice, and links Philbert. Please note, if you have any facial hair below your lips, the N95 mask is not acceptable for any "true" filtrant of your breathing air. I can't believe the amount of people that think they are safe with some of the mask they wear. My goatee is only 1/4 " of hair, and I tried 10 times to get the n95 to work, and it never past the test. This is why I have to wear the CAPR face mask with every patient I encounter for Covid testing. Think of it as an air filter that has a hole, or loose fit, the majority of every bit of intake of air comes thru the path of least resistance, same goes for masks.