Protecting Your Workers from Heat Stress

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National Institute for Occupational Safety and Health (NIOSH)

Summary Statement

This NIOSH poster explains the importance of gradually getting workers up to speed on a hot job. This process, acclimatization, is critical to avoid heat-related illnesses. The poster recommends that employers create a specific acclimatization plan that covers new workers and those with experience on the hot job.
July 2014

Develop an acclimatization plan

Acclimatization is the result of beneficial physiological adaptations (e.g., increased sweating efficiency and stabilization of the circulation) that occur after gradual increased exposure to a hot environment.

Tip 1

Gradually increase the time spent in hot environmental conditions over a 7-14 day period.

Tip 2

For new workers, the schedule should be no more than 20% exposure to heat on day 1 and an increase of no more than 20% exposure on each additional day.

Tip 3

For workers who have had previous experience with the job, the acclimatization schedule should be no more than:

  • Day 1 - 50% Exposure
  • Day 2 - 60% Exposure
  • Day 3 - 80% Exposure
  • Day 4 - 100% Exposure