When selecting protective garments, there are two primary ways to evaluate chemical barrier performance: permeation testing and the less-known and less-understood penetration testing.
Permeation testing typically applies to Level A garments that protect against unknown hazards or gaseous/vapor phase chemicals that represent the highest level of respiratory and skin threats. The penetration test method applies to Level B and Level C garments that protect against moderate-skin-threat liquid chemicals. (Note that there is no difference in EPA garment recommendations between Level B and Level C protection, because both levels provide protection from moderate skin threats. The difference is the type of respiratory protection provided.)