Reference

Assigned protection factors differ by country: OSHA credits every half mask 10, the UK runs a 4/10/20/40 ladder, EN 529 defines nominal factors with national APFs beneath, and Australia gates P3 to full facepieces. One master table, the three cross-border traps, and a four-jurisdiction worked selection example.

Face fit testing is the UK's proof that tight-fitting RPE actually seals. This guide covers INDG479's seven-exercise protocol, qualitative vs quantitative methods, Fit2Fit accreditation, the UK's 4/10/20/40 protection-factor ladder, CE vs UKCA status after Brexit, and a worked example fit-testing a site crew with a qualitative kit.