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645 Heat Injury and Illness Prevention: Employee Skip to main content

Preventive Measures

Ensuring Adequate Rest Breaks

When the adjusted heat index exceeds 80°F (WBGT > 70), employers must provide shaded, cool areas for rest and hydration breaks. The adjusted heat index is an accurate measure of how hot it really feels when the effects of humidity are added to high temperature.

This heat index chart shows risk levels for heat illness based on temperature and humidity.
  • Purpose: Rest breaks lower your body’s heat load by pausing work in a cooler spot.
  • Adjust with Heat: As heat levels rise above the action threshold, both the length and frequency of breaks should increase.
  • Optimize Recovery: Adding fans, misters, or air conditioning in the break area increases cooling and helps workers return to their tasks more comfortably—minimizing longer downtime.

The table below provides a simplified break schedule for workers that are acclimatized and unacclimatized to working in hot conditions (see ANSI A10.50-2024 Appendix 4). The chart identifies how many minutes per hour workers should work at specific temperatures.

Knowledge Check Choose the best answer for the question.

3-1. At what heat index are employers required to provide shaded, cool areas for workers to take rest and hydration breaks?