Reference

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.

Choosing a half mask respirator means matching the mask to your hazard, your face, and the cartridges you need - not just grabbing a popular model. This guide covers the assigned protection factor, elastomeric vs disposable, sizing, cartridge compatibility, the mandatory fit test, and the major brand series side by side.

A PAPR uses a blower to push filtered air into a hood or mask, giving higher protection and far more comfort than a tight-fitting respirator, often without a fit test. This guide explains how a powered air-purifying respirator works, its assigned protection factor, how it compares to half- and full-face respirators, and who actually needs one.

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.

OSHA 29 CFR 1926.103 is the construction respiratory protection standard. It requires all construction employers to comply with 29 CFR 1910.134 — including written programs, medical evaluations, and fit testing. This guide covers APF selection, silica and asbestos rules, common citation triggers and a worked example for concrete grinding.

OSHA requires a respirator under 29 CFR 1910.134 when engineering controls can't keep airborne exposure below the PEL, when a substance-specific standard mandates it, or in IDLH and emergency atmospheres. This guide covers the PEL trigger, required vs voluntary use, the written program, fit testing, APF selection, and a worked 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.