US respirator standards

OSHA 29 CFR 1910.134 — Assigned Protection Factors

The legally binding US standard. The Table 1 assigned protection factors were established by OSHA’s Assigned Protection Factors Final Rule (71 FR 50122, effective November 22, 2006) and remain current and unchanged as of 2026. The rule also defines the maximum use concentration: MUC = APF × exposure limit. APFs apply only when the respirator is used within a complete, effective respiratory-protection program (training, medical evaluation, fit testing, and maintenance).

See the full table on the how it works page, or the primary source: eCFR 29 CFR 1910.134.

ANSI/ASSP Z88.2-2015 — Practices for Respiratory Protection

A voluntary consensus standard (not law) and the latest edition (2015), now cited as ANSI/ASSP after ASSE renamed to ASSP in 2018. It goes beyond OSHA with a fuller program-management framework: its own APF/MUC selection logic, respirator-selection guidance for bioaerosols, mandatory wearer seal checks, required periodic program audits, and definitions harmonized with OSHA, NIOSH, and ISO. Employers under OSHA must still comply with 1910.134; Z88.2 is used as best-practice guidance. Source: ANSI webstore.

NIOSH Respirator Selection Logic (2004)

NIOSH Publication No. 2005-100 (October 2004) — still current. It guides respirator selection from a hazard assessment using the N/R/P filter classes (N95–P100), NIOSH-assigned APFs and MUCs, IDLH values, oxygen deficiency, and warning properties. It draws PEL/REL/IDLH values consistent with the NIOSH Pocket Guide to Chemical Hazards. Note: it is not intended for infectious agents or CBRN-terrorism agents. Source: NIOSH RSL 2004.

Recent activity (2023–2026)

• No changes to the OSHA APF table, OSHA PELs, or NIOSH REL/IDLH values relevant to selection during 2023–2026.
• 2024 — NIOSH proposed a rule (42 CFR Part 84) to establish a Combination Unit Respirator class by incorporating NFPA 1987. This is a device-approval standard, not a change to selection or APFs.
• 2025 — NIOSH NPPTL cut respirator-approval processing time by ~35% and granted 528 new approvals. Certification-throughput only; no effect on APFs, PELs, or selection logic.

A note on exposure limits

Many OSHA PELs date to 1971 and can be less protective than NIOSH RELs or ACGIH TLVs. The OSHA Annotated PEL tables list OSHA, Cal/OSHA, and NIOSH values side-by-side. This calculator lets you enter whichever exposure limit your program uses.

Reference only. Standards summaries here are for orientation; consult the primary sources and a qualified professional. This site is independent and not affiliated with OSHA, ANSI/ASSP, or NIOSH.