Reference

WBGT and the heat index are different quantities: one is a four-factor instrument reading occupational limits are written against, the other a shade-at-rest screen from temperature and humidity. This guide covers what each measures, the NIOSH workload limits, clothing adjustment factors, and when a phone weather reading fails a jobsite.

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.

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.