ASTM is undoubtedly one of the most important yet confusing aspect of face mask specifications. We'll break out what ASTM is and what you should look for when purchasing your face masks.
What is ASTM?
The American Society of Testing and Materials is actually a governing body that provides medical testing and rating of face masks products in the United States. Performance is based on bacterial filtration, synthetic blood penetration, breathing pressure, and sub-micron particulate filtration. It also tests and rates whether the materials used are flammable.
Difference in ASTM Levels
Is higher really better? Not quite.
In all of the levels above, it's easy to see that many mask manufacturers easily surpass the 95-98% PFE and BFE requirement to be certified by ASTM standards. The key difference, however, is in the fluid resistance. Level 1 masks provide basic resistance for bodily fluids caused by sneezing and coughing. Level 2 and above have much stricter requirements as they are considered surgical products and are used primarily by physicians, which tests and rates whether blood can penetrate the masks' layers, both inward and outward.
Level 2 and Level 3 masks are also often made from completely different meltblown and spunbond materials than Level 1 and should be worn only by professionals who work in medical environments.
But what about N95? Doesn't that just filter out 95%?
This is a completely different subject, but the key elements of why N95 respirators are useful against spreading airborne diseases is 1) the size of the particles it's able to filter, and 2) the mask's shape which provides a near hermetic seal. N95s are also not governed by ASTM, but rather NIOSH, the National Institute for Occupational Safety and Health.