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Heat Stress Prevention

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Heat Stress Prevention


Working in hot conditions may pose special hazards to safety and health. Since 1936, 30,000 people have died from heat related illnesses. On average, 384 people die each year during normal hot temperatures.

How the Body Handles Heat

Four environmental factors affect the amount of stress a worker faces in a hot work area: temperature, humidity, radiant heat (such as from the sun or a furnace) and wind speed. Individuals with high blood pressure or some heart conditions and people who take diuretics (water pills) may be more sensitive to heat exposure.

The body defends itself from heat through three mechanisms: breathing, sweating, and changing the blood flow. The first reaction is to circulate blood to the skin, which increases skin temperature and allows the body to give off some heat. During heavy work, muscles need more blood flow, which reduces the amount of blood available to flow to the skin and release the heat.

Sweating also helps the body to cool off, but only when the humidity levels are low enough to allow the sweat to evaporate and if water and salts lost through sweating is replaced.

At Risk Employees
Some employees are more likely to experience heat disorders than others. Younger employees and those more physically fit are often less likely to experience problems. Employees 65 years of age and older may not compensate for heat stress efficiently and are less likely to sense and respond to change in temperature. Employees with heart, lung or kidney disease, diabetes and those on medications are more likely to experience heat related stress problems. Diet pills, sedatives, tranquilizers, caffeinated drinks and excessive alcohol consumption can all exacerbate heat stress effects.

It often takes two to three weeks for employees to become acclimated to a hot environment. This acclimation can subsequently be lost in only a few days away from the heat. Thus employees should be more cautious about heat stress after coming back from a vacation, when beginning a new job, or after the season's first heat wave. In short, precautions should be taken anytime there are elevated temperatures (approaching 90 degrees Fahrenheit) and the job is physically demanding.

Other Factors
Other heat stress factors are also very important. In addition to temperature, increased relative humidity, decreased air movement, lack of shading from direct heat (radiant temperature), the type of clothing worn will all affect the potential for heat stress

Heat Stress Disorders
High temperatures and humidity stress the body's ability to cool itself, and heat illness becomes a special concern during hot and/or humid weather. There are three major forms of heat illness: heat cramps, heat exhaustion, and heat stroke. The following table identifies each condition, the signs and symptoms, and recommended first aid.

Heat Stress Disorders

Condition Signs and Symptoms First Aid
Heat Rash
Usually occurs in hot and humid environments where sweat cannot evaporate easily. If a rash covers a large area it may become very uncomfortable.

* Rash characterized by small pink or red bumps;
* Irritation or prickly sensation; and
* Itching
* Keep skin clean and dry to prevent infection;
* Wear loose cotton clothing;
* Take a cool bath or sit in the air conditioning to ease irritation;
* Some lotions help ease the pain and itching

Heat Cramps
Muscle spasms which usually affect the arms, legs, or stomach and generally occur from heavy exercise or intensive works done in hot environments. Inadequate fluid intake often leads to heat cramps.

* Cramping or spasms of muscles;
* May occur during or after work or a few hours later

* Rest briefly in a cool or shaded area and cool down;
* Drink an electrolyte containing drink such as Gatorade;
* If the cramps are severe or do not go away after 1 hour, seek medical attention

Heat Exhaustion
Is more serious than heat cramps. It occurs when the body's internal air-conditioning system is overworked, but hasn't completely shut down. It occurs because the body has lost large amounts of water and salt through excessive sweating.

* Cool, moist skin, ashen complexion;
* Headache;
* Intense thirst;
* Dizziness,
* Feeling faint;
* Low grade fever;
* Heavy sweating;
* Weak or tired;
* Rapid pulse rate, and/or low blood pressure.

* Move the person to a cool location and have them lie down with feet slightly elevated;
* Loosen or remove the person's clothing and apply cool wet cloths or direct a fan towards them;
* Drink cool water or an electrolyte containing drink such as Gatorade. Make sure the drink is not too cold and avoid caffeinated beverages such as colas, iced tea or coffee;
* Monitor the person closely. Heat exhaustion can quickly become heat stroke. If the person has a fever greater than 102° F, faints, has confusion or seizures call 911 for medical assistance

Heat Stroke
This is the most serious health-related illness. It is life threatening with high death rate if it is onset. Heat stroke occurs when the body has depleted its supply of water and salt and the victim's body temperature rises to deadly levels. The body is not able to regulate its core temperature.

* The victim stops sweating
* Rapid heartbeat;
* Rapid shallow breathing;
* Throbbing headache;
* Confused, has convulsions, and/or appears unconscious; and
* High body temperature of 104° F or higher
* Call 911 ASAP;
* Remove any unnecessary clothing and place the person on their side to expose as much skin surface as possible;
* Move to a cool area, out of direct sunlight;
* Cool the person by sponging or spraying with cool water;
* Fan vigorously to increase cooling;
* Apply ice packs to the groin, neck and arm pits;
* Monitor body temperature; and
* Do not give them fluids to drink

Heat Stress Prevention

* Allow time for employees to adjust to the summer heat. 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;
* Reduce the workload. Increase the use of equipment on hot days to reduce physical labor. Also, reduce the use of equipment that produces excess heat;
* Establish a schedule for work and rest periods during hot and humid days;
* Inform employees how to recognize signs and symptoms of heat stress disorders and be prepared to give first aid if necessary; and
* Avoid placing "high risk" employees in hot work environments for extended time periods. Realize individual employees vary in their tolerance to heat stress conditions.

* Use the Heat Stress Disorders table to recognize the signs and symptoms of heat stress;
* Pre-hydrate by drinking plenty of water or electrolyte containing drinks before work in hot environments is started. You should drink at least 8 oz of fluid every 20-30 minutes to stay hydrated. Drink BEFORE you are thirsty;
* Pace the work, taking adequate rest periods. The breaks should take place in an air conditioned environment. If air conditioning is not available, seek shelter in a cool or shady area;
* Keep shaded from direct sunlight or other heat sources where possible, for example, wear a hat and apply sunscreen;
* Work by using the buddy system on hot, humid days; and
* Wear light colored, loose (unless working around equipment with moving parts) clothing.

General Tips

Wear loose-fitting, lightweight clothing to allow sweat to evaporate. Light colors absorb less heat than dark colors. Wear a hat with a brim to keep the sun off head and face.

Drink plenty of fluids to replace fluids lost during sweating. Drink water and/or electrolyte containing drinks and avoid caffeinated beverages. Drink 16-32 ounces of cool fluids each hour. Drink BEFORE you are thirsty.

Work Schedule
Heavy work should be scheduled during the cooler parts of the day whenever possible. Rather than be exposed to heat for extended periods of time during the course of a day, employees should, wherever possible, be permitted to distribute the workload evenly over the day and incorporate work-rest cycles. Work-rest cycles give the body an opportunity to get rid of excess heat, slow down the production of internal body heat, and provide greater blood flow to the skin. Take more frequent breaks when working in extreme temperatures or at the first sign of heat stress symptoms.

Body Weight
Workers may be at greater risk if they lose more than 1.5% or their body weight in a single day from sweating.

Heat Stress Index
The heat stress index is a measure of how hot it really feels in degrees Fahrenheit when relative humidity is factored with the actual air temperature. This chart has been adapted from the National Weather Service's "heat index".

To read the table: find the temperature on the left hand side, and then move to the right until you find the column for the approximate relative humidity. That number will be the temperature that it will "feel" like. Example: A temperature of 95 degrees and relative humidity of 50% will "feel" like 107 degrees. Add up to 15 degrees if in the direct sun.