Predicted Heat Strain model estimating physiological strain from heat balance inputs.
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No standalone formula is published for this standard; see programmable logic and parameters below.
Baseline: mean radiant temperature = air temperature (no additional radiant load) · wind speed = 0.3 m/s · metabolic rate = 300 W (moderate work, FORMULAS.WORKLOAD_METABOLIC_W.moderate) · clothing insulation = 0.5 clo (this page does not supply a clothing value; computeISO7933 falls back to 0.5 clo when none is given — an internal calculator default, not a value specified by the ISO 7933 text itself).
| Air temp (°C) | 20% | 40% | 60% | 80% | 100% |
|---|---|---|---|---|---|
| 20 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr |
| 25 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr |
| 30 | 45 / 15 min work/rest per hr | 30 / 30 min work/rest per hr | 30 / 30 min work/rest per hr | 30 / 30 min work/rest per hr | 15 / 45 min work/rest per hr |
| 35 | 15 / 45 min work/rest per hr | 15 / 45 min work/rest per hr | 15 / 45 min work/rest per hr | Stop work | Stop work |
| 40 | Stop work | Stop work | Stop work | Stop work | Stop work |
| 45 | Stop work | Stop work | Stop work | Stop work | Stop work |
Required inputs: airTempC, meanRadiantTempC, relativeHumidity, windSpeedMS, metabolicRateW
Optional inputs: clothingInsulationClo
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Get notified when ISO 7933 Predicted Heat Strain (PHS) changes — threshold changes, scope and legal-status changes, additions and removals. Changes that permit more heat exposure than before are labelled as such.
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