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Heat Stress and Heat-Related Illness Prevention

Quick Tips #222

During the summer months, employers should be especially aware of the dangers associated with working in high-temperature environments. Heat and humidity combined with physical exertion can do more than just make employees uncomfortable—it can lead to a variety of heat-related illnesses that can debilitate employees.

Heat Cramps

Heat cramps are painful muscle spasms. They can occur after vigorous exercise or intense physical activity in extreme temperatures. Abdominals, calf and thigh muscles and the biceps/triceps are most frequently affected. If cramping occurs it is suggested to rest and cool down by drinking water with a teaspoon of salt per quart. Affected individuals may also feel faint and should be taken to a cool place and manual pressure applied to the cramped muscle.

Heat Rash

Heat rash, or prickly heat, appears as fine red spots or small bumps, usually found where clothing is somewhat restrictive (i.e., on the neck and upper back, chest or arms). This harmless rash is triggered by hot, humid weather when one is dressed too warmly for conditions. The rash develops when skin is persistently wet with perspiration. The small inflamed spots on the skin can become infected. The condition usually disappears when the skin is cooled and dried.

Heat Exhaustion

Heat exhaustion is a result of excessive heat and dehydration. It is generally caused by insufficient water intake, insufficient salt intake and a deficiency of the production of sweat, which evaporates on the skin to cool the body. Symptoms of heat exhaustion can have a sudden onset and include pale, clammy skin, fatigue, dizziness, nausea, vomiting, shallow breathing, rapid pulse and intense thirst. Syncope (fainting) is a milder form of heat exhaustion and is brought on by having to stand for long periods of time in a hot environment. It is caused by the pooling of blood in the heat-dilated vessels of the legs.

A victim of heat exhaustion should be cooled as rapidly as possible by placing the individual flat or with feet slightly elevated in front of a fan or in a cool room. Administer cool liquids (not icy), and seek medical attention. More severely exhausted patients may need I.V. fluids—especially if vomiting prevents them from keeping liquids down. Heat exhaustion is more difficult to diagnose than heatstroke, but its prognosis is far better unless circulatory failure is prolonged.


Heatstroke is caused by overexposure to extreme heat and a breakdown of the body's heat-regulating mechanisms. In the initial and most crucial stage of diagnosing heat stroke, a victim will exhibit an altered mental status, such as disorientation or confusion. This altered consciousness is the key to diagnosing heat stroke. All heat stroke victims will exhibit an altered mental state; this is not true for those suffering from heat exhaustion or extreme sunburn.

Victims of heat stroke often have hot, dry and flushed skin, a rapid heartbeat and abnormally high body temperature (i.e., a rectal temperature of 105.8°F or an oral temperature of 104.8 °F). The victim may appear confused or lose consciousness entirely. If body temperature is too high, death can occur.

Heat stroke is an extreme medical emergency requiring immediate medical attention. Until medical assistance is available, the victim should be cooled rapidly by placing him/her in a shaded area, submersing them in a cool bath or wrapping them in wet sheets. Air movement around the individual should be increased to improve evaporative cooling.

Another cooling method is to spray the victim with lukewarm water and fan the individual with a towel. The water evaporating from the skin will help cool the victim quickly. During the cooling process, the victim must be continuously monitored to prevent shivering. Once a victim's rectal temperature is reduced to 102.2°F (oral temperature of 101.2 °F), cooling methods should be stopped.

Even though it is important to replace fluids as soon as possible, liquids should NOT be administered to a victim in an altered mental state of heat stroke—there is a risk of these liquids being aspirated into the lungs. Medical professionals will give I.V. fluids to an individual suffering from heat stroke when they arrive at the scene.

Heat-Related Illness Prevention

Basic on-the-job heat-related illness prevention methods include the following:

  • Wear loose fitting clothing
  • Drink water often (don't wait until you're thirsty)
  • Schedule hot jobs for the cooler part of the day (early morning or late afternoon)
  • Schedule routine maintenance and repair work in hot areas during the cooler seasons of the year
  • Provide additional breaks and comfortable break areas
  • Add additional personnel to reduce exposure time for each member of a crew
  • Permit workers the freedom to interrupt work when they feel extreme heat discomfort

OSHA's Technical Manual discusses specific engineering and administrative control measures in great detail. It also outlines a variety of personal protective equipment that can be implemented to reduce the possibility of heat-related illnesses. This reference material is available from OSHA.

Understanding heat-related illness symptoms and prevention methods will help keep your employees safe and your workplace running smoothly during the summer months.

Commonly Asked Questions

Q.   There seems to be conflicting opinions on the use of salt tablets. When, if ever, are they appropriate for employee use?
A.   If the temperatures are extreme and the activity is intense, the use of a sport drink with sodium would be better than tablets. You need to have sodium because it helps the small intestine absorb water, getting it into the blood-stream faster. However, salt tablets are highly-concentrated doses of sodium that can interact with other medicines and health conditions and pose a health threat to employees if not administered by a health professional. Another reason to avoid tablets is that if the water lost through sweating is not replaced, salt can build up in your body and cause cramps. Too much sodium in your system can also cause fluid retention, which can cause your blood pressure to rise, predisposing you to such problems as swollen legs or arteriosclerosis. Generally, a fluid/electrolyte replacement sport drink is safer than tablets.
Q.   Are sport drinks any better than water for employees working in high temperature environments?
A.   The real key is to keep your self fully hydrated. According to a 1999 release from the Mayo Health Foundation, unless you are engaging in extreme exercise, water is your best bet. Sport drinks are generally not necessary unless you are exerting yourself for 90 minutes or more (60 minutes if the activity is particularly intense or temperatures are extreme). During physical work or exercise, it is recommended to replenish your fluids every 20 minutes. Your body has limits in its ability to adjust to fluid loss, so don't wait to be thirsty! Humans lose about 10 cups of fluid a day in sweat, urine, exhaled air and bowel movements. What is lost must be replaced to maintain balance. On the other hand, sport drinks really can’t hurt. There is some research that shows individuals will drink more of a sport drink than water, and that alone will help you stay adequately hydrated. Sport drinks quickly replace fluids and electrolytes that are lost in sweat. They also provide energy to working muscles. During extreme physical exertion or in very hot conditions, sport drinks are superior to water. While water is a good thirst quencher, it is not an efficient re-hydrator like a sport drink. This is because water can quench your thirst before you are completely rehydrated. Water also turns on the kidneys prematurely so you can lose fluid in the form of urine much more quickly than when drinking a sports drink. The small amount of sodium in most sports drinks aids your body to hold on to the fluid you consume rather than losing it through urine. The carbohydrates sports drinks contain make it more easily absorbed than water. One caution is to avoid the high-carbohydrate drinks, like soda, especially those in the 20% concentration range. Fluid carbohydrate levels exceeding 6 to 8% are actually more difficult for the body to absorb.



National Oceanic and Atmospheric Administration (Chart)

OSHA - Heat Illness Prevention Campaign

(Rev. 9/2014)

Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at

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Please Note:
The information contained in this publication is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This publication is not a substitute for review of the current applicable government regulations and standards specific to your location and business activity, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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