Heat kills more outdoor workers than any other weather hazard — and PPE makes it worse. Impermeable coveralls and multi-layer clothing trap body heat, so the air temperature alone understates the strain. Enter your conditions below and get work/rest guidance per hour in the style of OSHA / NIOSH / ACGIH heat-stress programs.
Effective heat value = heat index (°C) + ACGIH clothing adjustment (°C). Simplified NIOSH-style bands for acclimatized workers; your site's heat-illness prevention plan governs.
| Effective °C | Light work | Moderate work | Heavy work |
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Sweat is the body's air-conditioning. Evaporation carries heat away from the skin — but only if air can reach it. Vapor-barrier coveralls and multi-layer ensembles block that airflow, which is why ACGIH adds up to +11 °C to the WBGT for vapor-barrier suits. Two crews in the same weather can face very different risk: one in work shirts, one in chemical suits.
Acclimatization matters. These bands assume workers acclimatized to heat (roughly 1–2 weeks of progressive exposure). New or returning workers need a ramp-up schedule — OSHA recommends increasing workload gradually over 7–14 days. When in doubt, use the next stricter band.
Use it as a trigger, not a verdict. If the calculator says 30/30 and your crew is fine, keep watching — heat illness is individual. If anyone shows headache, dizziness, nausea or confusion, stop work and cool them immediately regardless of what any calculator says. Pair this with buddy checks, shaded rest areas, and your written heat-illness prevention plan.
Breathable, heat-conscious workwear and gloves — OEM/ODM from the manufacturer, matched to your hazard assessment.
Request bulk / OEM quote →Disclaimer: This tool provides general work/rest guidance based on published OSHA, NIOSH and ACGIH heat-stress concepts (NOAA heat-index regression, ACGIH clothing adjustment factors, NIOSH-style work/rest bands). It is not medical advice and does not replace your site's heat-illness prevention plan, a qualified EHS professional, or local regulations. On-site EHS judgment always governs.