Many employees work in occupations where they are exposed to hot, humid environments. In addition, some use special protective clothing and equipment that interferes with the body’s ability to dissipate heat and effectively maintain normal body temperature. Heat stress and heat-related illnesses can occur when the human body is exposed to hot temperatures for prolonged periods of time. When employees work in such environments, precautions should be taken to prevent heat-related illnesses. The concern is not merely for comfort, working in hot environments can cause sickness and even death if precautions are not taken to prevent overheating.
Normally, the human body maintains a constant internal temperature by regulating blood circulation and sweat glands. When the body is exposed to hot temperatures, or warm temperatures with high humidity, several things happen: first, the body increases circulation of blood to the skin’s surface to be cooled, much like the fluid in a car radiator. Then, the sweat glands begin to produce more sweat to cool the skin’s surface by evaporation.
If the air temperature near the skin’s surface is the same or warmer than normal core body temperature, the body is not able to cool itself effectively. If there is no air movement near the surface of the skin, or if the air is humid, sweating will continue, depleting the body of fluids and electrolytes, and the core body temperature will begin to rise higher than normal. When this occurs, it can be life-threatening. It is important to recognize the hazards of working in hot environments and the signs and symptoms of heat-related illnesses.
The most deadly heat-related illness is heat stroke. It occurs when the body has exhausted its ability to cool itself through sweating and circulation. The temperature regulatory system fails and sweating stops. This may occur with little warning to the employee and leave them unaware that a crisis stage has been reached. When heat stroke occurs, employee’s skin is hot, usually dry, red, or spotted. Their body temperature will be around 105 degrees or higher, and they can be mentally confused, delirious, in convulsions, or unconscious. Unless the employee receives rapid and appropriate treatment, brain damage and/or death can occur.
If signs or symptoms of heat stroke exist, call emergency medical services immediately and administer first aid. Move the employee to a cool area, thoroughly soak their clothing with water, and vigorously fan their body to increase cooling. Obtain further treatment at a medical facility to ensure recovery. Remember, heat stroke can be life-threatening.
Heat exhaustion is less serious than heat stroke, but may lead to heat stroke if not treated immediately. Heat exhaustion is caused by the loss of large amounts of fluid by sweating, sometimes causing excessive loss of salt and electrolytes. An employee suffering from heat exhaustion still sweats but experiences extreme weakness or fatigue, giddiness, nausea or headache. Their skin is clammy and moist and their complexion is pale or flushed. Body temperature is normal or only slightly elevated. In more serious cases, the employee may vomit or lose consciousness. An employee with heat exhaustion should rest in a cool place and drink plenty of liquids. With this treatment, those with mild cases usually recover spontaneously. Those with severe cases may require medical care by a physician.
Heat cramps are painful spasms of the muscles that occur when a person sweats profusely in a hot environment, tries to replace the body fluid by drinking water, but does not replace the salt loss. Drinking large quantities of water tends to dilute the body’s fluids, and the low salt level in the muscles causes painful cramps. All muscles may be affected, but usually the muscles performing work are most susceptible to cramps. Drinking salted liquids may relieve heat cramps.
Heat rash, also known as prickly heat, occurs when sweat is not easily removed from the surface of the skin by evaporation, and the skin remains wet most of the time. The sweat ducts become plugged, and a skin rash develops. The rash may spread or be complicated by infection. To prevent heat rash, rest in a cool place periodically throughout the day, and bathe and dry skin regularly.
Other Heat-Related Concerns
In addition to the heat-related conditions mentioned above, some employees may experience fainting. This can occur when an employee who is not accustomed to hot environments stands erect and immobile for long periods of time. The blood vessels in the skin and lower parts of the body enlarge to regulate the body’s temperature, and blood may pool rather than return to the heart to be pumped to the brain. Lack of blood to the brain causes fainting. To avoid fainting, move around and shift body weight from one leg to the other.
Employees who have heart problems, or are on a low sodium diet under the recommendation of a physician, should consult with their physician on how to handle working in hot, humid environments.
Prevention of Heat Stress
If your company has hot and/or humid work environments, take steps to protect employees from heat stress hazards. Establish a program for gradually acclimating employees to the hot environment. Consider the following elements in a program:
- Train employees to recognize heat-related illnesses. Train them in preventative measures and in proper first aid techniques to treat these illnesses.
- Encourage employees to drink five to seven ounces of water every 15 to 20 minutes throughout the day. In the course of a day’s work, the body may produce as much as two to three gallons of sweat. These fluids should be replaced at nearly the same rate as they are lost. Cool, clean, palatable drinking water should be readily available. Employees should not depend on thirst to signal when or how much water to drink since thirst is a poor indicator of the actual need for fluids.
- Where possible, use engineering controls such as mechanization of a process, installation of heat shields, or installation of ventilation, to remove the heat and/or humidity from the work environment.
- Allow new employees and those returning from an illness or vacation to gradually become accustomed to the heat. Require them to work for short periods in the heat and then work in other cooler jobs. The human body becomes acclimatized to the heat in about five to seven days. During this time, the body will undergo changes that will enable it to better withstand heat and humidity. The body will sweat more and will not lose electrolytes as quickly.
- Implement a program of work-rest cycles. Shorter work-rest cycles are required for more strenuous physical work and hotter environments. Work periods should be followed by periods of rest in a cooler environment (about 76 degrees). The American Conference of Governmental Industrial Hygienists (ACGIH) specifies ways to measure heat and humidity and outlines recommended work-rest cycles for different work loads in hot/humid environments. For more detailed information on this, consult the most recent TLV and BEI booklet published by the ACGIH. This booklet is published annually and can be ordered by calling (513) 742-2020 or by visiting acgih.org.
- Encourage employees to add extra salt to food if salt replacement is needed. Salt tablets should not be used.
- Use protective equipment such as reflective clothing, reflective face shields, or insulated or ventilated suits when necessary. There are vests and clothing available from safety equipment suppliers that utilize air streams or water inside of tubes to cool the employee. There are also items of clothing that contain pockets in which ice can be placed.
National Institute on Occupational Safety and Health (NIOSH), Working in Hot Environments, publication number 86-112. Copies are available at cdc.gov/niosh/homepage.html, or by calling (800) 35-NIOSH.
WCF Insurance Safety Department
NOTICE: This guide may make reference to the Occupational Safety and Health Administration (OSHA) regulations; however the guide is not legal advice as to compliance with OSHA or other safety laws, codes, or regulations. Compliance with OSHA and other safety laws codes or regulations, and maintaining a safe work environment for your employees remains your responsibility. WCF Insurance does not undertake to perform the duty of any person to provide for the health or safety of your employees. WCF Insurance does not warrant that your workplace is safe or healthful, or that it complies with any laws, regulations, codes, or standards.