Heat Stress – Recommendations

Control of Heat Stress | Training | Acclimatization | Hydration | Rest Breaks

Control of Heat Stress

Employers should reduce workplace heat stress by using engineering and administrative (work practice) controls. An engineering control could be a change to the design of the workplace that reduces exposure to heat. Administrative controls are changes to tasks or schedules to reduce heat stress.

Engineering controls might include those that:

• Increase air velocity.
• Use reflective or heat-absorbing shielding or barriers.
• Reduce steam leaks, wet floors, or humidity.

Work practice recommendations include the following:

• Limit time in the heat and/or increase recovery time spent in a cool area.
• Reduce the metabolic (physically difficult) demands of the job.
• Use tools intended to minimize manual strain.
• Increase the number of workers per task.
• Train supervisors and workers about heat stress.
• Use a buddy system where workers observe each other for signs of heat-related illnesses.
• Require workers to conduct self-monitoring and create a work group (i.e., workers, a qualified healthcare provider, and a safety manager) to make decisions on self-monitoring options and standard operating procedures.
• Provide adequate amounts of cool, potable water near the work area and encourage workers to drink often.
• Use a heat alert program whenever the weather service forecasts a heat wave.
• Institute a heat acclimatization plan and encourage increased physical fitness.

Training

Train workers before hot outdoor work begins. Tailor the training to worksite conditions.

Employers should provide a heat stress training program for all workers and supervisors about the following:

• Recognition of the signs and symptoms of heat-related illnesses and administra­tion of first aid.
• Causes of heat-related illnesses and steps to reduce the risk. These include drinking enough water and monitoring the color and amount of urine output.
• Proper care and use of heat-protective clothing and equipment and the added heat load caused by exertion, clothing, and per­sonal protective equipment.
• Effects of other factors (drugs, alcohol, obesity, etc.) on tolerance to occupational heat stress.
• The importance of acclimatization.
• The importance of immediately reporting any symptoms or signs of heat-related illness in themselves or in coworkers to the supervisor.
• Procedures for responding to symptoms of possible heat-related illness and for contacting emergency medical ser­vices.

Supervisors should also be trained on the following:

• Implementing appropriate acclimatization.
• What procedures to follow when a worker has symptoms of heat-related illness, including emergency response procedures.
• Monitoring weather reports.
• Responding to hot weather advisories.
• Monitoring and encouraging adequate fluid intake and rest breaks.

Acclimatization

Acclimatization is the result of beneficial physiological adaptations (e.g., increased sweating efficiency, etc.) that occur after gradual increased exposure to a hot environment. Employers should ensure that workers are acclimatized before they work in a hot environment.

• Gradually increase workers’ time in hot conditions over 7 to 14 days.
• For new workers, the schedule should be:

• • No more than 20% of the usual duration of work in the heat on day 1.
  • No more than 20% increase on each additional day.

• For workers with previous experience, the schedule should be:
  • No more than 50% of the usual duration of work in the heat on day 1
  • No more than 60% of the usual duration of work in the heat on day 2
  • No more than 80% of the usual duration of work in the heat on day 3
  • No more than 100% of the usual duration of work in the heat on day 4.
• Closely supervise new employees for the first 14 days or until they are fully acclimatized.
• Workers who are not physically fit need more time to fully acclimatize.
• Acclimatization can be maintained for a few days of non-heat exposure.
• Taking breaks in air conditioning will not affect acclimatization.

NIOSH Acclimatization Fact Sheet

Hydration

Employers should provide the means for appropriate hydration of workers.

• Water should be potable, <15°C (59°F), and made accessible near the work area.
• Estimate how much water will be needed and decide who will get and check on water supplies.
• Provide individual drinking cups for each worker.
• Encourage workers to hydrate themselves.

Workers should drink an appropriate amount to stay hydrated.

• For moderate activities in the heat that last less than 2 hours, drink 1 cup (8 oz.) of water every 15–20 minutes.
• If sweating lasts for several hours, drink sports drinks containing balanced electrolytes.
• Avoid alcohol and drinks with high caffeine or sugar.
• Generally, fluid intake should not exceed 6 cups per hour.

NIOSH Hydration Fact Sheet

Rest Breaks

Employers should ensure and encourage workers to take appropriate rest breaks to cool down and hydrate.

• Permit rest and water breaks when a worker feels heat discomfort.
• Modify work/rest periods to give the body a chance to get rid of excess heat.
• Assign new and unacclimatized workers lighter work and longer, more frequent rest periods.
• Shorten work periods and increase rest periods:
  • As temperature, humidity, and sunshine increase.
  • When there is no air movement.
  • If protective clothing or equipment is worn.
  • For heavier work.

NIOSH Work/Rest Schedules Fact Sheet