Reference

OSHA permissible exposure limits live in three separate tables that work three different ways, and 29 CFR 1910.1000(d) supplies the arithmetic for deciding whether a measured exposure is over the limit. This guide works both formulae with real numbers, decodes the ceiling and peak columns, and explains why most PELs date from 1971.

Ototoxic chemicals — certain solvents, metals, asphyxiants and medications — damage hearing on their own and multiply the risk of noise-induced hearing loss, sometimes below exposure limits. Covers the OSHA/NIOSH 2018 bulletin, the chemical classes, affected industries, and how to fold ototoxicants into a hearing program.

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.

Respirator cartridge colors follow ANSI K13.1 (required by 42 CFR 84.193): black = organic vapor, white = acid gas, magenta = P100 HEPA. This guide decodes all ten color classes, combination cartridge color bands, brand-by-brand model number mapping for 3M, Honeywell North, and Moldex, and what the colors do not tell you about a.

Can You Reuse an N95: N95 filtering facepiece respirators (FFRs) are designated as single-use devices under NIOSH's 42 CFR Part 84 approval system. NIOSH does not approve any N95 for routine reuse.

NIOSH vs. OSHA Explained (2026 Guide): NIOSH (National Institute for Occupational Safety and Health) is a research and certification agency within the CDC that approves PPE and sets recommended exposure limits.