Heat Stress Index
Heat Stress Index — Occupational Heat Exposure Assessment
Overview
The Heat Stress Index is a composite measure used to evaluate the thermal stress experienced by workers in hot environments — combining air temperature, radiant heat, humidity, and air movement to produce an index value that reflects the actual heat burden on the human body rather than air temperature alone. Multiple heat stress indices exist — including the Wet Bulb Globe Temperature, the Belding -Hatch Heat Stress Inde x, and the Predicted Heat Strain model — each with specific applications and validity ranges. In occupational settings, heat stress indices are used to determine safe work -rest ratios, identify when conditions exceed safe working thresholds, and assess the risk of heat exhaustion and heat stroke in workers performing physically demanding tasks in hot environments.