Line Contractor

How Heat Affects the Body

Heat Safety
Published On
Sep 8, 2021


Upon completing this training, the employee will be able to:

  • Understand how heat adversely affects their body

  • Know conditions and symptoms associated with working in hot weather

Your body temperature is meant to remain fairly constant no matter what is happening outside. To prevent the body from overheating, excess heat—from both external sources (i.e., hot weather) and what’s generated from working—must be removed. This removal is an automatic response that turns on when the body temperature is higher than 98.6°F. Cooling begins by sending more blood to the skin’s surface, which enables heat to be transferred from the body to the cooler air. As part of the cooling process, sweat glands produces sweat, which cools the skin and body as it evaporates. When the air temperature gets close to body temperature, this system doesn’t cool the body efficiently.

Sweating is the only way for a body to effectively cool itself. On days with high humidity, even sweating doesn’t work well. High temperature and high humidity combined reduce workers’ ability to get tasks done. Since so much blood goes to the skin to cool the body, there is less blood for the muscles, brain and other vital organs. This can result in a loss in overall strength and causes fatigue to set in. It also decreases alertness and ability to concentrate, which is likely to increase the potential for accidents. Heat can also cause slippery hands from sweating, dizziness and decreased physical performance. Higher body temperature and physical discomfort increases irritability, anger and emotional states. Workers can overlook safety procedures and practices as well as miss potentially hazardous situations.


Most heat-related health problems result from how well the body can process this excess heat. 

  • Heat stroke is the most serious hot-weather health issue. It occurs when sweating no longer effectively reduces body temperature. The situation can reach a crisis level quickly and with little warning. Someone suffering from heat stroke has skin that appears hot, dry, red or spotted. The body temperature will reach 105°F or higher, causing the victim to become mentally confused or delirious, sometimes convulsing or falling unconscious. Without immediate medical treatment, brain damage or death can occur.

  • Heat exhaustion can appear similar to the early symptoms of heat stroke. It is caused by dehydration and salt loss from excessive sweating. Unlike heat stroke, a worker with heat exhaustion will still sweat and have clammy, moist, pale or perhaps flushed skin. The body temperature remains near normal, but the worker experiences extreme weakness or fatigue, giddiness, nausea or headache. Resting in a cool place and drinking plenty of liquids can reverse this.

  • Dehydration and salt loss can also cause painful heat cramps. Low salt levels in the muscles will cause cramping. Tired muscles (those used to do the work) are most likely to cramp, but muscles of the legs, arms or abdomen can also be affected.

  • Heat can also cause less devastating issues. To a person unused to working in a hot environment, fainting and heat fatigue are possibilities. Lightheadedness and fainting can be remedied by lying down to send blood back throughout the body. Heat fatigue is discomfort and strain from prolonged heat exposure. It can be lessened with gradual adjustment to heat. 

  • Anyone suspected of suffering from any of these heat related problems should be taken seriously and treated promptly to reduce any further injury.

Discussion Questions:

  • How does the body prevent heat from building up in hot weather?

  • Why does extremely hot weather increase the potential for accidents?

  • What are the symptoms of heat stroke?

  • What are effective ways to deal with heat-related conditions?

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