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Western Kentucky University

Environmental Health and Safety - Heat Illness

Heat Illness

High temperature and high humidity may lead to heat illness, which can be serious or even life threatening.

For people working outdoors in hot weather, temperature & humidity affect how hot they feel.  Temperature and humidity are factors in determining the heat index, or the "feels like" temperature. The higher the heat index, the hotter the weather feels. In addition, working in direct sunlight or wearing protective clothing can make conditions "feel" up to 15° F hotter than the heat index temperature!  Do you want to get the current heat index on your smart phone? There's an app for that!

Heat illness is preventable provided you get plenty of water, adequate rest, and frequent breaks in the shade.  Do not depend on thirst as a signal of when and how much to drink.  Instead drink five to seven ounces of fluids every fifteen to twenty minutes to replenish necessary fluids. Take frequent breaks especially if working outside, and find (or create) a shade to rest.

Heat stroke is the most serious heat-related disorder. It occurs when the body becomes unable to control its temperature: the body's temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. When heat stroke occurs, the body temperature can rise to 106° F or higher within 10 to 15 minutes. Heat stroke can cause death or permanent disability if emergency treatment is not given.


Symptoms of heat stroke include:

  • Hot, dry skin or profuse sweating
  • Hallucinations
  • Chills
  • Throbbing headache
  • High body temperature
  • Confusion/dizziness
  • Slurred speech

First Aid:

  • Call 911 and notify their supervisor.
  • Move the sick person to a cool shaded area.
  • Cool the person using methods such as:
    • Soaking their clothes with water.
    • Spraying, sponging, or showering them with water.
    • Fanning their body.


Heat exhaustion  is the body's response to an excessive loss of the water and salt, usually through excessive sweating. Workers most prone to heat exhaustion are those that are elderly, have high blood pressure, and those working in a hot environment. 


Symptoms of heat exhaustion include:

  • Heavy sweating
  • Extreme weakness or fatigue
  • Dizziness, confusion
  • Nausea
  • Clammy, moist skin
  • Pale or flushed complexion
  • Muscle cramps
  • Slightly elevated body temperature
  • Fast and shallow breathing

First Aid:

  • Have them rest in a cool, shaded or air-conditioned area.
  • Have them drink plenty of water or other cool, nonalcoholic beverages.
  • Have them take a cool shower, bath, or sponge bath.

 Other forms of heat illness include Heat Syncope (fainting) | Heat Cramps | Heat Rash

When working in the heat remember to pace yourself and drink plenty of fluids.  Avoid beverages that contain alcohol or caffeine.  Wear lightweight, light colored, loose-fitting clothing.  Be aware that poor physical condition, some health conditions and some medications increase the risk for heat illness.

Heat Index Risk Level Protective Measures
Less than 91°F Lower (Caution) Basic heat safety and planning
91°F to 103°F Moderate Implement precautions and heighten awareness
103°F to 115°F High Additional precautions to protect workers
Greater than 115°F Very High to Extreme Triggers even more aggressive protective measures

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 Last Modified 9/24/14