The human body functions best within a narrow internal temperature range of 36 to 38 degrees Celsius. In hot environments, more blood is directed toward the skin surface and perspiration increases to help cool the body. When heat loss or gain becomes more than the body can balance, internal systems will begin to fail and shut down, leading to illness and possibly death.

Dehydration is a common concern when working in a hot environment. It is caused by failure to replace the salt and water lost through perspiration. Although perspiring helps the body cool, it is necessary to replace lost fluid and salt.

On average, one to two cups of water per hour are required to replace fluid lost from heavy perspiration. Sugary drinks such as soda pop, and fluids containing caffeine and alcohol should be avoided. Cool, but not cold, water should be provided in a location convenient to workers. Because the feeling of thirst may not be enough to ensure adequate water intake, workers in hot environments should be encouraged to drink at least one cup per hour. Too much water (more than two cups) should not be taken at one time since workers may develop abdominal cramps.

Most people consume enough salt as table salt and as naturally occurring salt in foods. Fruit and vegetable juices can be good sources of natural salt. Encourage workers on salt-restricted diets to discuss salt needs with their doctor. Salt tablets should only be taken on a doctor's advice.

Factors other than the environment and workload can influence the body's ability to cope with heat. To avoid heat related illness, such factors should be taken into consideration when assigning worker tasks and deciding on control measures.

Workers should ask a health professional whether any drugs being taken may increase the risk of heat illnesses. Age generally brings a decrease in efficiency of sweat glands, heart and lungs (after age 45). Gender is an influencing factor since men tend to have a higher sweat rate and larger oxygen intake, and therefore tend to acclimatize better than women. Fitness, size and other factors affect the differences in people's ability to cope.

Personal protective equipment may be necessary, including:

Wear insulated or cooled clothing for short-term exposure such as maintenance jobs

Wear clothing that allows free movement of airflow

Wear heat reflective clothing near heat sources such as a hot furnace

Wear light-filtering eye protection when work involves hot objects such as molten metals

Use sunscreen and sun block when working outdoors

Wear a hat and light clothing to protect skin when working in the sun