Prevent Heat Illness with Acclimatization
Make sure workers drink enough liquids, and give them rest breaks. You should also acclimatize your workers by gradually increasing the time they work in hot environments.
A recent Morbidity and Mortality Weekly Report presented 20 cases of heat-related illnesses or death of workers. In most of these cases employers had no program to prevent heat illness, or programs were deficient. Acclimatization was the most common program element missing and most clearly associated with worker death.
Tips for Acclimatizing Workers
Workers become acclimatized to heat when they gradually work for longer periods in a hot environment. Benefits of acclimatization include physiological adaptations, such as increased sweating efficiency and stabilization of the circulation. Employers must make certain that workers acclimatize to heat by gradually increasing the time they work in hot environments.
Acclimatizing workers requires following a plan:
- New workers, and workers returning from an absence of more than a week, should follow a schedule to gradually acclimatize to the hot conditions. Begin with 20% of the usual duration of work in the hot environment on the first day, increasing gradually by no more than 20% each day that follows.
- Experienced workers should begin on the first day of work in excessive heat with 50% of the usual duration of work. They should work 60% on the second day, 80% on the third day, and 100% on the fourth day.
- Depending on individual or environmental factors, it might take up to 14 days or longer for a worker to become fully acclimatized.
Other Tips for Preventing Heat-Related Illness and Death
Employers should check on workers throughout their shift to make sure they are drinking enough liquids, getting enough rest, and not showing signs of heat-related illnesses. Urge workers to take regularly scheduled rest breaks in shaded or air-conditioned areas, and provide them water. A worker should drink about 1 cup every 15 to 20 minutes during moderate activities in moderately hot temperatures. Employers should regularly monitor the worksite temperature using the heat index and/or wet bulb globe index. Employers should modify work schedules to reduce heat exposure when possible. All workers and managers should be trained to recognize signs and symptoms of heat-related illnesses and know what to do for basic first aid.
NIOSH is working to revise a guidance document with more recommendations for safety and health professionals and employers. Check the NIOSH website in the future for the updated NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments. The draft version is currently publicly available on the NIOSH Heat Stress website.