Work out work rest cycle in heat instantly with clear inputs, formula shown and shareable results.
Threshold limit values for heat set a WBGT ceiling for continuous work that falls as metabolic rate rises and is lower for unacclimatised workers. Above that ceiling the permissible work fraction falls, and the standard response is a work rest cycle within each hour, taken in a cooler recovery area so the body sheds accumulated heat.
Continuous work ceiling
Ceiling WBGT falls about 1.5 °C for every 100 W above 300 W metabolic rate, and is 2 °C lower for unacclimatised workers
Work fraction
Fraction falls approximately 25 percent per °C of WBGT above the ceiling
Preliminary estimate only. Work rest scheduling in heat must follow the applicable heat stress standard and be supervised by a competent person with physiological monitoring where appropriate.
Ceiling WBGT falls about 1.5 °C for every 100 W above 300 W metabolic rate, and is 2 °C lower for unacclimatised workers. Threshold limit values for heat set a WBGT ceiling for continuous work that falls as metabolic rate rises and is lower for unacclimatised workers.
Yes, ideally. Resting in the same conditions allows only limited recovery, so the rest fraction has to be much larger. A shaded, ventilated or air conditioned recovery area is the effective control.
This calculator takes 3 inputs: Wet bulb globe temperature, Metabolic rate, Worker status. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.