The University of Iowa
Environmental Health and Safety

Heat Stress

What is Heat Stress?

Heat stress occurs when the body cannot get rid of excess heat. When this happens, the body's core temperature rises and the heart rate increases. As the body continues to store heat, the person begins to lose concentration and has difficulty focusing on a task, may become irritable or sick, and often loses the desire to drink. The next stage is most often fainting and even death if the person is not cooled down.

Factors that contribute to heat stress are high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, and strenuous physical activities.

Contact information and areas of expertise can be found on the Contact Us page.

Documents

Heat Illness and Injury Prevention Plan 

Training

  • Heat Stress - W552OS 
    • This course covers the signs, symptoms and treatment of heat-related illnesses and how to prevent them from happening.
    • Audience: All employees working for more than 15 minutes in an area (inside or outside) with a heat index above 80°F are required to take this training annually. Supervisors and departmental safety staff are recommended to take this course on a yearly basis. 

For further training and registration information, go to EHS Safety Training. 

Heat Rash

Also known as prickly heat, is skin irritation caused by sweat that does not evaporate from the skin. Heat rash is the most common problem in hot work environments.

Symptoms

  • Clusters of red bumps on skin
  • Often appears on neck, upper chest, folds of skin

First Aid

  • Try to work in a cooler, less humid environment when possible
  • Keep the affected area dry

Heat Cramps

Are caused by the loss of body salts and fluid during sweating. Low salt levels in muscles cause painful cramps. Tired muscles—those used for performing the work—are usually the ones most affected by cramps. Cramps may occur during or after working hours.

Symptoms

  • Muscle spasms
  • Pain

First Aid

  • Have worker rest in shady, cool area
  • Worker should drink water or other cool beverages
  • Wait a few hours before allowing worker to return to strenuous work
  • Have worker seek medical attention if cramps don't go away

Heat Exhaustion

Is the body's response to loss of water and salt from heavy sweating? 

Symptoms

  • Cool, moist skin
  • Heavy sweating
  • Headache
  • Nausea or vomiting
  • Dizziness
  • Light headedness
  • Weakness
  • Thirst
  • Irritability
  • Fast heartbeat

First Aid

  • Have worker sit or lie down in a cool, shady area
  • Give worker plenty of water or other cool beverages to drink
  • Cool worker with cold compresses/ice packs
  • Call 911 if signs or symptoms worsen or do not improve within 60 minutes.
  • Do not return to work that day

Heat Stroke

The most serious form of heat-related illness happens when the body becomes unable to regulate its core temperature. Sweating stops and the body can no longer rid itself of excess heat.

Symptoms

  • Confusion
  • Fainting
  • Seizures
  • Excessive sweating or red, hot, dry skin
  • Very high body temperature

Treatment

  • Call 911
    • Then
      • Place worker in shady, cool area 
      • Loosen clothing, remove outer clothing
      • Fan air on worker; cold packs in armpits
      • Wet worker with cool water; apply ice packs, cool compresses, or ice if available
      • Provide fluids (preferably water) as soon as possible 
      • Stay with worker until help arrives 
  • Monitor the heat index or wet bulb globe temperature throughout the day.
  • Allow time for employees to adjust to hot jobs when possible. It often takes two to three weeks for an employee to become acclimated to a hot environment.
  • Adjust the work schedule, if possible. Assign heavier work on cooler days or during the cooler part of the day.
  • Establish a schedule for work and rest periods during hot days with break areas being cooler than the work areas.
  • Train workers to recognize signs and symptoms of heat stress disorders and be prepared to give first aid if necessary.
  • Drink at least one quart of fluids per hour of work in the heat.

To determine if it is too hot the wet bulb globe temperature (WBGT) or the heat index need to be measured and compared to the initial and high heat triggers in the Heat Illness and Injury Prevention Plan.   

The heat index for outside locations can be found on most weather apps as well as on the OSHA NIOSH Heat safety tool app for Android or IOS. 

External Links

Occupational