Workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational illnesses and injuries. Heat stress can result in heat stroke, heat exhaustion, heat cramps, or heat rashes. Heat can also increase the risk of injuries in workers as it may result in sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam.
Workers at risk of heat stress include outdoor workers and workers in hot environments such as firefighters, bakery workers, farmers, construction workers, miners, boiler room workers, factory workers, and others. Workers at greater risk of heat stress include those who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat.
Prevention of heat stress in workers is important. Employers should provide training to workers so they understand what heat stress is, how it affects their health and safety, and how it can be prevented.
TYPES OF HEAT STRESS:
Heat stroke is the most serious heat-related disorder. It occurs when the body becomes unable to control its temperature: the body's temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. When heat stroke occurs, the body temperature can rise to 106 degrees Fahrenheit or higher within 10 to 15 minutes. Heat stroke can cause death or permanent disability if emergency treatment is not given.
Symptoms of heat stroke include:
Take the following steps to treat a worker with heat stroke:
Heat exhaustion is the body's response to an excessive loss of the water and salt, usually through excessive sweating. Workers most prone to heat exhaustion are those that are elderly, have high blood pressure, and those working in a hot environment.
Symptoms of heat exhaustion include:
Treat a worker suffering from heat exhaustion with the following:
Heat syncope is a fainting (syncope) episode or dizziness that usually occurs with prolonged standing or sudden rising from a sitting or lying position. Factors that may contribute to heat syncope include dehydration and lack of acclimatization.
Symptoms of heat syncope include:
Workers with heat syncope should:
Heat cramps usually affect workers who sweat a lot during strenuous activity. This sweating depletes the body's salt and moisture levels. Low salt levels in muscles causes painful cramps. Heat cramps may also be a symptom of heat exhaustion.
Muscle pain or spasms usually in the abdomen, arms, or legs.
Workers with heat cramps should:
Heat rash is a skin irritation caused by excessive sweating during hot, humid weather.
Symptoms of heat rash include:
Workers experiencing heat rash should:
Recommendations for Employers
Employers should take the following steps to protect workers from heat stress:
Recommendations for Workers
Workers should avoid exposure to extreme heat, sun exposure, and high humidity when possible. When these exposures cannot be avoided, workers should take the following steps to prevent heat stress:
NIOSH: Criteria for a Recommended Standard: Occupational Exposure to Hot Environments (Revised Criteria 1986)
This document presents the criteria, techniques, and procedures for the assessment, evaluation, and control of occupational heat stress by engineering and preventive work practices. Included are ways of predicting health risks, procedures for control of heat stress, and techniques for prevention and treatment of heat-related illnesses.
NIOSH: Working in Hot Environments
Workers who are suddenly exposed to working in a hot environment face additional and generally avoidable hazards to their safety and health. This publication discusses the safety and health consequences of heat stress.
Health Hazard Evaluations
Other Government Resources
Occupational Safety and Health Administration (OSHA) Safety and Health Topics: Heat Stress
Provides a guide to information regarding the recognition, evaluation, control, and compliance actions involving heat stress.
OSHA Technical Manual Section III: Chapter 4 - Heat Stress
Provides descriptions of heat disorders, investigative guidelines, sampling methods, control, and PPE.
OSHA Sawmills eTool: Heat Stresses
Provides information on the hazards of heat stress and possible solutions or controls.
OSHA Fact Sheet: Protecting Workers from Effects of Heat [PDF - 22 KB]
Provides information that will help workers understand what heat stress is, how it may affect their health and safety, and how it can be prevented.
OSHA Fact Sheet: Working Outdoors in Warm Climates [PDF - 25 KB]
Hot summer months pose special hazards for outdoor workers who must protect themselves against heat, sun exposure, and other hazards. Employers and employees should know the potential hazards in their workplaces and how to manage them.
NOAA: Heat Wave - A Major Summer Killer [PDF - 268 KB]
Provides general information regarding the recognition and control of heat stress.
Mine Safety & Health Administration (MSHA): Heat Stress - What to Do.
Provides documents related to heat stress in the mining industry.
United States Department of Agriculture (USDA): Wildland Fire Safety - Heat Stress
This brochure focuses on the risks of heat stress, and what the firefighter should do to minimize those risks.
American National Standards Institute (ANSI) - Ergonomics of the Thermal Environment: Analytical Determination and Interpretation of Heat Stress Using Calculation of the Predicted Heat Strain
This document specifies a method for the analytical evaluation and interpretation of the thermal stress experienced by a subject in a hot environment. It describes a method for predicting the sweat rate and the internal core temperature that the human body will develop in response to the working conditions.
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ANSI - Ergonomics of the Thermal Environment: Medical Supervision of Individuals Exposed to Extreme Hot or Cold Environments
This International Standard provides advice to those concerned with the safety of human exposures to extreme hot or cold thermal environments.
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ANSI - Hot environments: Estimation of the Heat Stress on Working Man, Based on the WBGT-index (Wet Bulb Globe Temperature)
This document gives a method, which can easily be used in an industrial environment for evaluating the stresses on a individual. It applies to the evaluation of the mean effect of heat on man during a period representative of his activity but it does not apply to very short periods, nor to zones of comfort.
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