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.

Assigned protection factors (APF) are the protection levels OSHA assigns to each respirator class in 29 CFR 1910.134 Table 1. This guide decodes the APF table from quarter mask to pressure-demand SCBA, shows how APF and the exposure limit set the maximum use concentration, and works an example of picking a respirator from a measured exposure.

Most OSHA PELs derive from 1968 ACGIH TLVs and have not been updated since 1971 — ACGIH updates TLVs annually. For many chemicals the TLV is 5–20× lower than the PEL, requiring a higher APF respirator. ANSI/ASSP Z88.2 directs employers to use the most protective OEL. This guide covers the practical selection implications.

OSHA 29 CFR 1910.134 governs respiratory protection programs across general industry and construction. This guide covers every major section: written programs, APF selection, medical evaluations, fit testing, user seal checks, cartridge change-out, IDLH requirements, training, recordkeeping, and a step-by-step compliance example.