- High temperatures (90°F or above can cause heat stress);
- High humidity (sweat doesn’t evaporate rapidly);
- Intense radiant heat (such as from the sun or a furnace); and
- Low air velocity (lowers the rate at which sweat evaporates).
- Mental confusion, delirium, loss of consciousness, convulsions or coma;
- Rapid pulse;
- Body temperature of 106°F or higher; and
- Hot dry skin which may be red, mottled, or bluish.
- A variety of engineering controls including general ventilation and spot cooling by local exhaust ventilation at points of high heat production can lower heat levels. Shielding provides a source of protection from radiant heat sources. Evaporative cooling and mechanical refrigeration will reduce heat. Additionally:
- Eliminate steam leaks;
- Use cooling fans;
- Modify equipment;
- Use power tools to reduce manual labor; and
- Provide personal cooling devices or protective clothing to reduce the hazards of heat exposure.
- Work practices such as providing plenty of drinking water — as much as a quart per worker per hour — at the workplace can help reduce the risk of heat disorders. Train first aid workers to recognize and treat heat stress disorders. Provide the names of trained staff to all workers.
Consider an individual worker’s physical condition when determining his or her fitness for working in hot environments. Older workers, obese workers, and those on some types of medication are at greater risk.
- Alternating work and rest periods with longer rest periods in a cool area can help workers avoid heat stress. If possible, schedule heavy work during the cooler parts of the day and provide protective clothing. Train supervisors to detect early signs of heat stress. Allow stressed workers to interrupt their work if they are extremely uncomfortable.
- Acclimatization to the heat through short exposures followed by longer periods of work in the hot environment can reduce heat stress. A physiological adaptation occurs with repeated exposure to hot environments:
The ability to acclimatize varies among workers. Generally, individuals in good physical condition acclimatize more rapidly than those in poor condition.
- Heart rate will decrease,
- Sweating will increase,
- Sweat will become more dilute, and
- Body temperature will be lower.
Approximately one week of gradually increasing the workload and time spent in the hot environment will usually lead to full acclimatization. On the first day the individual performs 50 percent of the normal workload and spends 50 percent of the time in the hot environment. Each day an additional 10 percent of the normal workload and time is added, so that by day six, the worker is performing the full workload for an entire day. The exposure time should be at least two hours per day for acclimatization to occur.
Acclimatization is lost when exposure to hot environments does not occur for several days. After a one week absence, a worker needs to reacclimatize by following a schedule similar to that for initial acclimatization. The acclimatization will occur more rapidly, so increases in workload and time can increase by approximately 20 percent each day after the first day, reaching normal work conditions by day four.
New employees and workers returning from an absence of two weeks or more should have five-day period of acclimatization. This period should begin with 50 percent of the normal workload and time exposure the first day and gradually building up to 100 percent on the fifth day.
- Employee education is vital so that workers are aware of the need to replace fluids and salt lost through sweat and can recognize dehydration, exhaustion, fainting, heat cramps, salt deficiency, heat exhaustion, and heat stroke as heat disorders. They need to know they should be drinking at least five to seven ounces of cool water every 15-20 minutes and to avoid taking salt tablets. Salt tablets irritate the stomach and can lead to vomiting, which can result in further dehydration.
What happens to the body?
What should be done?
What happens to the body?
What should be done?
- Slowly build up tolerance to the heat and the work activity (usually takes about two weeks).
- Perform the heaviest work in the coolest part of the day.
- Take frequent short breaks in cool shaded areas. This allows their body’s to cool down.
- Drink plenty of cool fluids.
- Taking certain medications. Have employees check with their doctor, nurse, or pharmacy to find out if any medicines they are taking are affected by hot environments.
- Individuals have had a heat-induced illness in the past.
- Wearing personal protective equipment (like respirators or protective suits).