Recognizing Heat Stress Hazards: Tips for Effective Training

Sept. 1, 2003

Heat Stress and the Aircraft Maintenance Industry:
General guidelines for preventing heat stress

By Justin Bruursema


Heat stress is a serious workplace hazard for millions of workers across the nation. The dangers of heat stress include rashes, fainting, exhaustion, and even death. On average, excessive heat exposure causes 34 worker deaths and 2,420 occupational injuries and illnesses involving days away from work per year, according to 2002 data from the Bureau of Labor Statistics. The Occupational Safety and Health Administration reported that five of the workers died from heat-related injuries during a single 14-day period between late July and early August of 2000. This brief article aims to help employees understand the risks associated with heat stress and best safety practices to avoid suffering from adverse effects of heat.

Workers in the aircraft maintenance sector are particularly at risk given their regular exposure to high temperatures, heated metals, and over-heated confined spaces. Additionally, high temperatures can hamper the precision required for many aircraft maintenance tasks.

Heat also presents many secondary hazards. We all know from experience that too much heat makes us irritable, uncomfortable, and less alert. Accidents can also occur due to the slipperiness of sweaty palms, dizziness, or fogging safety glasses. The potential for burns from accidental contact with hot surfaces is also a possibility.

Proper safety training on heat stress and its associated hazards is vital for the health and well-being of workers. It is good business as well as a humane approach to be sure employees are alert to the warning signals their bodies issue under heat stress and are prepared to respond for their personal health and safety - and that of their co-workers, as well.

Heat stress: Risk factors

The central factors that contribute to heat stress are temperature, humidity, air movement, physical activity, clothing worn, and the radiant temperature of the surroundings. Temperature alone seldom causes heat stress. Hazardous situations are usually caused by a combination of factors.

When heat is combined with other stresses such as hard physical labor, loss of fluids, or fatigue, the potential for heat stress increases. You do not need to be in a tropical climate or a hot desert to suffer the effects of heat stress. Heat stress disorders can occur in boiler rooms, confined spaces, during HAZMAT rescue operations, and in many other work situations.

Situations involving aircraft maintenance present their own unique heat stress risks. Aluminum and other sheet metals and alloys used for aircraft bodies, wings, and other parts are easily heated by the sun and or high air temperatures. Often aircraft maintenance requires entry into tight and confined spaces where temperatures can be significantly higher than normal working conditions.

Anyone can suffer from heat stress. Many workers assume that because they are young and in good physical shape that they are immune to heat stress. While some people are at a greater risk of developing symptoms than others, anyone could become a victim of heat illness if environmental conditions overwhelm your body's ability to regulate its temperature.

Your body is constantly working to maintain a normal internal temperature of about 98.6 F. But when heat causes your temperature to rise faster than your body can cool itself off, you can become vulnerable to heat stress. Heat stress is any condition caused when environmental conditions overwhelm your body's temperature regulating abilities. Your body can't cool itself off fast enough - causing you to overheat.

Heat stress: Effects on the body

To understand how heat stress occurs, let's look at how the body regulates its temperature. The human body continuously works to maintain its core temperature at 98.6 F (37 C). The body compensates for small upward or downward changes in temperature by activating its built-in thermoregulatory system, controlled by temperature sensors in the skin. When the body is hot it has to get rid of excess heat. It does this in two ways: increasing blood circulation and sweating.

The body's initial reaction to temperature rises is to lower internal body temperature by increasing the blood circulation to the skin so that excess heat can escape through the skin. But if the body's muscles are being used for physical activity, less blood is available to flow to the skin.

Sweating is another way the body releases heat. When increased blood flow does not lower the core temperature, the body will produce sweat. When this moisture reaches the skin surface, it evaporates and cools the body down. Sweating is only effective if humidity levels are low enough to allow evaporation to take place, and if the fluids lost by the body are replaced.

If the body cannot reduce its temperature through increased blood circulation and sweating, it will begin to store the heat. When this happens, you run the risk of serious health hazards.

When you continue to labor at the same pace in growing heat, your body loses fluids and becomes fatigued. The increasing heat stress results in poorer job performance by lowering your alertness and slowing physical responses. As the brain loses vital blood fuel that has gone off to fight the heat, you may no longer be able to even recognize your body's natural warning symptoms.

Symptoms of heat-related illnesses can range from rashes and sunburns to cramps, exhaustion, and heat stroke. Heat rashes, sunburns, and heat cramps can be painful and uncomfortable, but they are not life threatening. Heat exhaustion and heat stroke are more serious conditions. If a co-worker suffers from a heat illness, your ability to recognize the symptoms and apply the proper treatment can be vital to saving a life. Let us take a closer look at some of the physical symptoms.

Heat rash

Early warnings of approaching heat stress often are overlooked as routine heat discomfort. An example is heat rash. Some call it "prickly heat," which develops when the skin remains wet, as sweat does not evaporate. It's common during humid periods of heat when sweat on the skin is slow at evaporating. This clogs the sweat ducts, and a skin rash appears. Relief comes from bathing the affected areas, then drying the skin. Heat rash involves discomfort more than danger.

Fainting and fatigue

If you feel dizzy or faint, it likely is a result of standing upright and motionless in the heat. Not moving causes blood to pool-a tendency for blood to flow through heat-enlarged blood vessels and collect in the lower areas of the body, leaving the brain without adequate replenishment. Often walking or moving around can offset the dizziness. At the first sign of dizziness or fainting, lie down. If that is not possible, sit down and put your head between your legs. As your head clears, get back on your feet and start moving around to prevent continued blood pooling. In any case, don't ignore any bodily warnings, as they can lead to more serious levels of heat stress:

Heat cramps

Heat cramps are painful muscle spasms that are caused by lack of salt in the body. They usually result from sweating heavily and drinking large amounts of water without replacing the body's salt loss. While water is needed to keep the body from dehydrating, drinking large quantities of it dilutes the body's fluids. This shortage of salt in the muscles causes sudden, painful spasms in the affected areas. Cramps usually affect tired muscles first, and sometimes don't hit until after work hours. Cramps may hurt, but they alert you that you need to ease up the work pace before the problem advances to the more dangerous areas of heat exhaustion and stroke. Replace the salt your body has lost by drinking a .5 percent solution of salt water or a sports drink. Rest in a cool place away from the sun. Lightly massaging the cramped muscles can bring some relief.

Heat exhaustion

Continued loss of fluid and salt from sweating can lead to heat exhaustion. The victim sometimes mistakes the symptoms for the flu. Symptoms can include heavy sweating, cool and moist skin, and a weak pulse. Other symptoms can include possible fainting, weakness, dizziness, nausea, diarrhea, blurred vision, and a normal or slightly high body temperature. The advanced stages of heat exhaustion can cause vomiting or loss of consciousness.

Heat exhaustion is a step away from heat stroke, and treatment can be more effective because the victim often remains conscious. Move the victim into a cooler, shaded area. Recline the victim with the feet elevated. Loosen clothing. A conscious person can replenish lost body fluids by drinking cool beverages, slowly but steadily. Avoid the use of ice or cold liquids. Pouring cool water over their body may help the victim. If untreated, heat exhaustion can develop into heat stroke.

Heat stroke

Heat stroke is the most serious of the heat illnesses. When sweating no longer helps the body regulate its internal temperature, the body has no choice but to halt cooling efforts and store the heat. The victim may be slightly confused and disoriented. Body temperature may be 105 F or higher. Other symptoms are delirium, convulsions, or even unconsciousness. This condition can be life threatening. There are two main types of heat stroke: classic and exertional.

Classic heat stroke may take days to develop and usually affects the poor, elderly, chronically ill, overweight, and alcoholics. Victims of classic heat stroke are not usually sweating. Exertional heat stroke affects healthy people who work or play hard in a warm environment. These victims are usually sweating when they develop heat stroke. Because it occurs rapidly, there usually isn't time for severe dehydration to occur. The skin will be hot, and it may or may not be dry. It is often red or spotted.

Heat stroke is a medical emergency. If a heat stroke victim does not receive the proper treatment quickly enough, death can occur. Do whatever you can to cool the victim off immediately. This includes moving the person into the shade, submerging him in water or pouring water on him, and fanning the victim. Avoid ice or very cold water, which constricts the blood vessels of the skin and prevents heat from escaping through the skin. While someone is cooling the victim down, another person should call for medical attention. If the victim is still conscious, try to get him to take sips of cool water.

Understanding and recognizing the causes and symptoms of heat stress disorders is an important part of heat stress safety. But the key is using measures to prevent heat stress from occurring in the first place. Heat stress is a stress on the body. The heat can affect your physical abilities and mental alertness. So it is not surprising that accidents in the workplace increase as the temperature rises. Let's take a look at what you can do to prevent heat stress.

Best safety practices for preventing heat stress

Engineering measures should be the first means of controlling this hazard. The most effective control measure when indoors is reducing the temperature of the work area. When this is not possible, other measures such as shielding or ventilation should be used. Use a fan or open a window to increase air movement.

The loss of fluids is the major contributor to heat illnesses. Under normal conditions your body loses about 2 quarts of water every day. When exposed to excess heat while working, a person can lose almost 2 quarts in one hour through sweating. This is why it is important to drink plenty of liquids before, during, and after working in warm environments.

If you know you will be working in a warm environment, you should begin drinking fluids before you start work. While working, you should drink at least 8 ounces of fluid every 20 to 30 minutes - even if you don't feel thirsty. Thirst is not a good indicator of when to drink fluids. If you wait until you are thirsty before you drink, you will be more likely to become dehydrated. Avoid alcoholic beverages and caffeine drinks because they increase water loss and cause dehydration. The best fluids to drink are water and sports drinks.

Since sweating is an important cooling mechanism, the moisture vapor transport rating of material used for protective clothing should be considered when selecting and using personal protective equipment. When hazard protection is not a concern, select clothing that is light weight, loose, and breathable. Wear light colors because they tend to reflect the heat. When working in the sun make sure you wear a hat and don't give in to the temptation to remove clothes. A sunburn may look healthy, but it greatly reduces the skin's ability to shed excess heat.

Most heat illnesses occur in the first few days of working in the heat. To prevent this, acclimation (adjusting to the heat) is very important. Gradually increase your exposure to warm temperatures. Most people are completely acclimated in four to seven days.

Take more frequent breaks when working in the heat and at the first sign of heat stress symptoms. Don't overdo it. Work at a comfortable pace. If you can, alternate job tasks so you are not in the heat for extended periods of time. Schedule more physical tasks for the morning or evening hours when temperatures are cooler. Reduce manual labor by using mechanical assistance whenever possible.

A healthy diet and body can help prevent heat illness. Excess weight traps heat in your body and forces your heart and glands to work harder to get rid of it. Other risk factors include alcohol consumption, caffeine, and old age. Exercise regularly and eat a healthy, balanced diet. Consult your doctor about exposure to heat if you have an existing medical condition, or are taking medication, or are overweight.


The above guidelines should be part of any heat stress prevention training program. Creating a respect and awareness of the hazards heat stress presents will greatly reduce the amount of heat stress related incidents and accidents.

As an aircraft maintenance professional, you need to adapt the above best safety practices to the specifics of your job functions. No one knows your specific situations better than yourself. Apply best safety practices to meet your exact workplace needs.

Justin Bruursema is a producer at Summit Training Source, for the past 22 years, the leading provider of environmental, health, and safety training programs. Summit offers over 600 training programs in multiple formats, including interactive CD-ROM and online training. You can preview any Summit program by going to