In the US, NIOSH (National Institute for Occupational Safety and Health) approved N95 respirators or filtering facepiece respirators (FFR) need to be marked with an approval number which can be verified on the NIOSH Certified Equipment List (CEL) or the NIOSH Trusted-Source page. NIOSH-approved FFRs will always have one the following designations: N95, N99, N100, R95, R99, R100, P95, P99, P100.