Course 602 - Heat and Cold Stress Safety

Safety guides and audits to make your job as a safety professional easier

Heat Stress and Safety

Safety Memo - Hot Enough For You?


People suffer heat-related illness when the body’s temperature control system is overloaded. The body normally cools itself by sweating. However, in some conditions, sweating isn’t enough. In such cases, a person’s body temperature rises rapidly. Very high body temperatures may damage the brain or other vital organs.

Several factors affect the body’s ability to cool itself during extremely hot weather. When the humidity is high, sweat will not evaporate as quickly, reducing the body’s ability to release heat quickly.

Other conditions that can limit the ability to regulate body temperature include:

  • Old age
  • Youth (ages 0-4)
  • Obesity
  • Fever
  • Dehydration
  • Heart disease
  • Mental illness
  • Poor circulation
  • Sunburn
  • Prescription use
  • Alcohol use
Occupational Safety and Health Administration

OSHA Regulations

Although there is not a specific OSHA standard for heat stress, employees are protected under the “General Duty Clause of the OSH Act” because heat –related illnesses are a serious hazard.

The general duty clause states that employers are required to “… provide a place of employment free from recognized hazards that are causing or likely to cause death or serious physical harm to its employees.”

sweaty worker
Sweating is necessary for the body to get rid of excess heat.
Make sure you drink enough cold liquids if you are working in extreme heat.


For the human body to maintain a constant internal temperature, the body must get rid of excess heat. This is achieved primarily through sweating. The evaporation of sweat cools the skin, releasing large amounts of heat from the body. As surrounding temperatures reach normal skin temperature, cooling of the body becomes much more difficult. If the air temperature is warmer than the skin, blood brought to the body surface cannot lose its heat. Sweating doesn’t cool the body unless the moisture is removed from the skin by evaporation. When there is high humidity, the evaporation of sweat from the skin is decreased and the body’s efforts to maintain a normal body temperature may be impaired.

Affected by Heat

Workers, who are exposed to hot and humid conditions, including the outdoors, factories and hot kitchens, are at the most risk for heat illness. Workers doing heavy work or wearing bulky protective clothing and equipment are also at risk. Some workers also might be at a greater risk than others if they haven’t built up a tolerance to hot conditions. Humans are able to adjust to the heat. Employers can reduce the chance of employees experiencing heat-related illnesses by gradually exposing them to hot environments for longer periods of time. This process usually takes about 5-7 days.

Heat-Related Illnesses

Excessive exposure to hot environments can cause a variety of heat-related health problems. Body temperature can rise to dangerous levels if precautions are not taken immediately. Heat illnesses can range from heat rash and cramps to heat exhaustion and heat stroke.

Heat Rash

Heat rash occurs in hot, humid environments.
Heat cramps are painful muscle spasms.

Heat rash often occurs in hot, humid environments where sweat doesn’t evaporate from the skin. The sweat ducts become clogged and result in a rash. Heat rash can be very uncomfortable. Victims of heat rash will see clusters of red bumps on the skin. The rash usually appears on the neck, upper chest and folds of the skin. To prevent heat rash, employees should work in cooler and less humid environments, if possible. Also, make sure to keep the affected area dry.

Heat Cramps

Heat cramps may happen alone or with other heat-related illnesses. They are painful muscle spasms caused by dehydration while performing hard physical labor in a hot environment. The cramps may be caused either by too much or too little salt. Tired muscles are also very susceptible to heat cramps.


If a worker experiences heat cramps, (usually caused by too much salt in the body due to sweating) employers should:

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

Heat-Related Illnesses (Continued)

Heat Exhaustion

Heat exhaustion causes weakness or light-headedness.

Heat exhaustion is caused by the loss of large amounts of fluid. This can happen by sweating and sometimes with an extensive loss of salt. An employee suffering from heat exhaustion still sweats, but may also experience the following symptoms:

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


Have the affected worker lie down or sit in a cool or shady area. The victim will need to drink plenty of cool liquids, preferably a sports drink with carbohydrates and electrolytes. You should also spray water or apply cool, wet cloths to the victim’s head and torso. Using a fan can also speed evaporation and lower the body temperature. If signs or symptoms get worse or do not improve in about an hour, the patient should be taken to a medical clinic or hospital to be evaluated by medical staff.

Real-Life Scenario

A young worker arrived for her shift at a vineyard. She was pregnant, and her job required her to spend long hours tying grapevines in the sun. As the day wore on, the temperature soared, eventually reaching triple digits. After nine hours of work, she collapsed from heat exhaustion. Two days later, she was dead. She was 17 years old.

Heat-Related Illness (Continued)

Heat Stroke

Heat stroke is the most serious heat-related illness. It occurs when the body’s temperature-regulating system fails and sweating becomes an inadequate way of removing excess heat. Heat stroke requires immediate medical attention and can result in death. When heat stroke doesn’t kill immediately, it can shut down major body organs causing acute heart, liver, kidney and muscle damage, nervous system problems, and blood disorders.

Signs an employee may be suffering from heat stroke are:

Heat stroke is the most serious heat-related illness.
  • Confusion
  • Fainting
  • Seizures
  • Excessive sweating or red, hot, dry skin
  • Very high body temperature
  • Unconscious


There are several steps to take when you notice someone showing the signs of heat stroke. Once you have called for emergency help, lay the victim on his or her back unless he or she is unconscious. Make sure to remove any objects close by if the victim has a seizure. If the worker is conscious, provide cool water to drink. Also, place ice packs under the armpits and in the groin area to cool them down.

Real-Life Scenario #1

On August 1st, 2006, a 44-year-old Hispanic migrant farm worker died after succumbing to heat stroke while working in a tobacco field on a farm in North Carolina. The victim arrived on the farm from Mexico on July 21st, 2006 and he was assigned to work in the tobacco fields, where he worked for the next week. On August 1st, 2006, it was hot and humid with a heat index (a measure of the combined effects of high temperatures and high humidity on the body) between 100 and 110. He had been working in a tobacco field when around 3 pm, he complained to the crew leader that he wasn’t feeling well. The victim drank some water and was driven back to his housing and left alone to rest. A short time later, he was found unconscious on the steps of the house. Emergency medical service (EMS) personnel were immediately called and responded within five minutes. The victim was taken to the hospital where his core body temperature was recorded at 108 Fahrenheit and was pronounced dead. Heat stroke was listed as the death on the death certificate.

Real-Life Scenario #2

On June 27th, 2003, a 41-year-old male laborer died from heat stroke one day after being taken to the hospital. The laborer was working on an addition to a factory sawing boards to make concrete forms. He worked until 5:00 pm that day and was in the parking lot on his way to his car when he apparently collapsed. A worker on the second shift at the factory was taking scrap material outside to a dumpster when he found the victim on the ground. The company receptionist called EMS and the supervisor went to the parking lot to administer emergency care to the laborer until EMS arrived. When paramedics arrived, they recorded the laborer’s body temperature as 107 Fahrenheit. He was transported to a local hospital where he died the next day with an internal body temperature of 108 Fahrenheit.

To prevent similar incidents from occurring, investigators made the following recommendations:

  • Employers should train supervisors and employees to recognize symptoms of heat exhaustion/stroke when working in high heat index and/or humid conditions.
  • To avoid dehydration and heat stress/stroke, employees should be given frequent breaks and be provided water and other hydrating drinks when working in humid and hot conditions.
  • Work hours should be adjusted to accommodate environmental work conditions such as high heat index and/or high humidity.

Preventing Heat Illnesses


Remember these three simple words: water, rest, shade! Employers should educate their workers on how taking water breaks often and limiting the time in the hot weather can help prevent heat illnesses. They should also include these prevention steps in worksite training and plans. Employers should also teach employees to gradually build up to heavy work in hot conditions. This helps workers become acclimated to the heat or build a tolerance to the hot temperatures. Finally, during the first week of work, employers should gradually increase workloads and allow more frequent breaks.

Check out this short audio clip by Dan Clark of the Heat stroke, heat exhaustion, heat syncope, heat cramps and heat rash are all covered in this podcast. Dan tells you how to guard against them, and how to treat them.

Engineering Controls

The basic concept behind engineering controls is the work environment and the job itself should be designed to eliminate hazards or reduce exposure to hazards.

Engineering controls can be simple in some cases. They are based on the following principles:

  • If feasible, design the facility, equipment, or process to remove the hazard or substitute something that is not hazardous.
  • If removal is not feasible, enclose the hazard to prevent exposure in normal operations.
  • Where complete enclosure is not feasible, establish barriers or local ventilation to reduce exposure to the hazard in normal operations.
Installing an air conditioner, like this one, is a good example of an engineering control.

There are several engineering controls that can be used if employees work in a hot environment. The best way to prevent heat illness is to make the work environment cooler. In outdoor situations, this may be done by scheduling activities during the cooler times of the day. However, very early starting times may result in increased fatigue. Also, humidity tends to be higher in the early morning hours. Employers can also provide air conditioned or shaded areas close to work areas and allow frequent rest breaks.

Indoor workplaces may be cooled by using air conditioning or increased ventilation, assuming that cooler air is available from the outside.

Other methods to reduce indoor temperature include:

  • Providing reflective shields to redirect radiant heat
  • Insulating hot surfaces
  • Use of fans

Work Practices

Work practice and administrative controls are closely related attempts to change behaviors. They are management-dictated work practices and policies to reduce or prevent exposures to temperature factors.

There are several work practice controls an employer can do to try and prevent heat-related health effects. Here are some examples:

  • Train workers and supervisors about the hazards leading to heat stress and ways to prevent them.
  • Allow workers to get used to hot environments by gradually increasing exposure over a 5-day work period.
  • Provide workers with plenty of cool water in convenient, visible locations close to the work area.
Drinking Water
Employers need to remind workers to drink small amounts of water consistantly.

Employers need to remind workers to drink small amounts of water before they become thirsty to maintain good hydration. Simply telling them to drink plenty of fluids is not sufficient. During moderate activity, in moderately hot conditions, at least one pint of water per hour is necessary. Workers should drink about six ounces or a medium-sized glass-full every 15 minutes. Instruct workers that urine should be clear or lightly colored.

Last Words

That’s a lot of important information! In the next module, we will take a look at cold stress safety. For now, it’s time for the first module quiz! Good luck!


This exercise is optional. To complete the exercise you must speak to trainer John and answer his questions. To do so, you will need to select a response at the bottom of the screen. Do your best to answer his questions. Good luck!


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. According to the text, which of the following is NOT a condition that could limit the ability to regulate body temperature?

2. Sweating doesn’t cool the body unless the moisture is removed from the skin through _________________.

3. Heat exhaustion is the most serious heat-related illness.

4. Which of the following are symptoms of heat stroke?

Have a great day!

Important! You will receive an "error" message unless all questions are answered.