Prevention of Heat Stress
The human body gains or loses heat in four ways: radiation (infra-red rays from hot objects), convection (transfer to or from air moving over the skin), conduction (direct transfer of heat or cold through direct contact), and evaporation of sweat from the skin. In hot work environments, conduction, radiation and convection often cause the body to gain heat instead of losing it. Then, evaporation of sweat becomes the body's most important, and often only, cooling method. Most people will lose about a quart of sweat an hour while working in extreme heat, making it vitally important that a person drinks plenty of fluid. Therefore, when working in hot environmental conditions, it is important to drink cool, not ice-cold water every 15 to 20 minutes, even if not thirsty (thirst is not a reliable guide to the body's need for water in hot work conditions). As a rule of thumb, a person needs to drink sufficient water to insure urination about once every two hours during working hours (whether one is sweating or not!). Failure to urinate for four hours or more in extreme heat indicates a severe dehydration situation, and plenty of water should be immediately consumed to prevent onset of heat stress symptoms and to restore and assure routine urination.
Heat exhaustion develops from excessive loss of fluid and/or salts from the body as workers get to a state where they are "not thirsty". The complexion becomes pale or flushed as the worker begins to experience weakness, clammy skin, fatigue, confusion, dry mouth, dizziness, muscle incoordination, nausea, and/or headache. The solution is simple: upon recognition of one or more of these signs in yourself or a co-worker, the affected person should remove themselves from the exposure, rest in a cool shaded place and drink plenty of appropriate fluids. If these symptoms persist, consult Employee Occupational Health Services.
Sweating results in the loss of not only body fluids, but also minerals, particularly among those persons who are not yet acclimated to the heat, or those with certain health problems such as high blood pressure. Such mineral losses can result in "heat cramps"(painful spasms of the bone muscles) if these salts are not replaced by food or water. Certain commercial drink mixes (such as Gatorade, Squincher, Powerade, etc.) are available which are designed to provide these electrolytes with water, and may be helpful.
Other factors, which are important in the prevention of heat exhaustion/stress are: the avoidance of coffee, alcohol or other dehydrating fluids; the eating of light, nutritious meals (fatty foods are harder to digest in hot weather), the wearing of loose light-colored, comfortable, cotton clothing; the use of shady areas, cooling fans or air conditioning, if and when available; getting used to the heat gradually over several days (proper acclimatization); getting enough sleep.