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Acclimatization is the beneficial physiological adaptations that occur during repeated exposure to a hot environment. These physiological adaptations include:

  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • The ability to perform work with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.

To acclimatize workers, gradually increase their exposure time in hot environmental conditions over a 7-14 day period. New workers will need more time to acclimatize than workers who have already had some exposure.

Acclimatization schedule

  • For new workers, the schedule should be no more than a 20% exposure on day 1 and an increase of no more than 20% on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than a 50% exposure on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.

In addition, the level of acclimatization each worker reaches is relative to the initial level of physical fitness and the total heat stress experienced by the individual.

Maintaining acclimatization

Workers can maintain their acclimatization even if they are away from the job for a few days, such as when they go home for the weekend. However, if they are absent for a week or more then there may be a significant loss in the beneficial adaptations leading to an increased likelihood of heat-related illness and a need to gradually reacclimate to the hot environment.

Some additional information on maintaining acclimatization:

  • It can often be regained in 2 to 3 days upon returning to a hot job.
  • It appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits which also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.