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Safety Article #11
It's summertime! Heat Safety
Many people spend at least part of their working day in a hot environment. Workers in foundries, laundries, construction projects, utilities, and bakeries - to name a few industries - often face hot conditions which pose special hazards to safety and health.
Environmental factors
Four environmental factors affect the amount of stress that workers face in hot work areas:
High temperatures (90 degrees 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).
Physical factors
Some of the most important factors affecting stress are personal characteristics such as age, weight, fitness, medical conditions, and acclimatization to the heat. The body reacts to high external temperature by circulating blood to the skin which increases skin temperature and allows the body to give off excess heat. However, if the muscles are being used for physical labor, less blood is available to flow to the skin and release the heat.
Sweating is another means the body uses to maintain a stable internal body temperature. Sweating is effective only if the humidity level is low enough to permit evaporation, and if the fluids and salts lost are adequately replaced.
Steps to reduce the risk of heat stress include moving to a cooler place, reducing the work pace or load, or removing or loosening some clothing. If the body cannot dispose of excess heat, the body's core temperature rises and the heart rate increases.
As the body continues to store heat, the individual begins to lose concentration and has difficulty focusing, may become irritable or sick, and often loses the desire to drink. Heat disorders include heat stroke, heat exhaustion, heat cramps, fainting (heat syncope), and heat rash.
How to keep cool in summer heat
Most heat-related health problems can be prevented or the risk of developing them reduced. The two most important methods are hydration and acclimatization, which increases the body’s ability to tolerate heat stress. Engineering and administrative controls are also important.
Engineering controls to lower heat levels include general ventilation and spot cooling by local exhaust ventilation at points of high heat production; shielding to provide a source of protection from radiant heat sources; and evaporative cooling and mechanical refrigeration. Additionally, you should:
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 - can help reduce the risk of heat disorders. Train first aid workers to recognize and treat heat stress disorders.
Consider an individual'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 greatest risk.
Alternate hot work with break periods in cool areas. 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.
Acclimatize to the heat starting with short exposures and building up to longer periods of work in the hot environment. A physiological adaptation occurs with repeated exposure to hot environments:
Heart rate will decrease,
Sweating will increase,
Sweat will become more dilute, and
Body temperature will be lower.
About one week of gradually increasing the workload and time spent in the hot environment usually leads to full acclimatization. On the first day the worker performs 50 percent of the normal workload and spends 50 percent of the time in the hot environment. For 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.
A little knowledge goes a long way
Workers need to know what to do to reduce the risk of extremely elevated body temperature. Training will help them to be aware of the need to replace fluids and salt lost through sweat and to recognize dehydration, exhaustion, fainting, heat cramps, salt deficiency, heat exhaustion, and heat stroke as heat disorders.
Together, informed employers and their employees can reduce or eliminate heat hazards and keep the working environment a safe and healthy place
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