Reference

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.

OSHA 1910.134(f) requires annual fit testing for all tight-fitting respirators. This guide covers 4 QLFT protocols (isoamyl acetate, saccharin, Bitrex, irritant smoke), 3 QNFT protocols (generated aerosol, PortaCount, CNP), pass/fail fit factor thresholds, the facial hair rule, recordkeeping, and a 6-step full-face APR onboarding example.

What Happens If a Respirator Doesn't Fit: A respirator that does not seal properly against the face stops working as rated. Fit failure collapses the assigned protection factor (APF) - a half-face respirator with an APF of 10 can deliver as little as 2× protection if the face seal leaks.