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NIOSH REL/RAL Logarithmic Curve — Heat Stress Screening Thresholds

NIOSH REL/RAL screening equations for acclimatized and unacclimatized workers.

Open NIOSH REL/RAL Logarithmic Curve in the interactive Guidance Wiki →

Authority
NIOSH
Jurisdiction
Global
Legal status
Guidance
Rule type
Screening Limit
Standard ID
HGC-005

Governing formula

RAL = 59.9 - 14.1 log10(M); REL = 56.7 - 11.5 log10(M)

Screening thresholds

Acclimatized workers

WBGT (°C)Light
180 W		Moderate
300 W		Heavy
415 W		Very heavy
520 W
2430.8°C limit28.2°C limit26.6°C limit25.5°C limit
2530.8°C limit28.2°C limit26.6°C limit25.5°C limit
2630.8°C limit28.2°C limit26.6°C limit25.5°C limit — exceeded
2730.8°C limit28.2°C limit26.6°C limit — exceeded25.5°C limit — exceeded
2830.8°C limit28.2°C limit26.6°C limit — exceeded25.5°C limit — exceeded
2930.8°C limit28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3030.8°C limit28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3130.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3230.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3330.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3430.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3530.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded
3630.8°C limit — exceeded28.2°C limit — exceeded26.6°C limit — exceeded25.5°C limit — exceeded

Unacclimatized workers

WBGT (°C)Light
180 W		Moderate
300 W		Heavy
415 W		Very heavy
520 W
2428.1°C limit25°C limit23°C limit — exceeded21.6°C limit — exceeded
2528.1°C limit25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
2628.1°C limit25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
2728.1°C limit25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
2828.1°C limit25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
2928.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3028.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3128.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3228.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3328.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3428.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3528.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded
3628.1°C limit — exceeded25°C limit — exceeded23°C limit — exceeded21.6°C limit — exceeded

Inputs

Required inputs: wbgtC, metabolicRateW

Optional inputs: acclimatization

Sources

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