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Physical Environment: Heat Stess

Choosing the right personal protective equipment can be a complex task. This guide can help you choose equipment that keeps workers safe and healthy, and makes your facility more productive.

When preparing to work in extremely hot or cold environments, take the same care you would if you were crossing an icy lake: ease in and watch carefully for signs of trouble. Experts advise having workers slowly ease into the heat or cold so their bodies can become acclimated.

After working in 90-degree temperatures all summer long, for example, a sudden cold spell can throw the body off. By spending two or three hours a day outdoors instead of eight, workers can build a tolerance to the heat or cold. The human body usually adjusts to the change in climate within five to seven days, according to the National Institute for Occupational Safety and Health (NIOSH).

Education and training is the safety manager's best assurance that workers know how extreme heat and cold can affect them. Address proper attire for weather conditions and make sure workers know how to be prepared for the conditions.

In cold environments, workers should change wet shoes and socks as soon as possible. It is important to eat often throughout the day and to drink plenty of fluids (the U.S. Army recommends 16 ounces before every meal). It is also important to keep active while outdoors in cold climates. During breaks, seek shelter or at least find a way to be shielded from wind and precipitation.

In hot environments, hourly breaks to cool down are recommended and frequent drinks are necessary to keep the body from dehydrating. NIOSH recommends workers drink five to seven ounces of fluids every 15 to 20 minutes in the heat. Workers who feel lightheaded should sit in a shady place and drink water or electrolyte replacement drinks often.

Clothing can make a big difference in protecting workers from extreme cold or heat.

In cold environments, experts say the only way to stay warm is to dress in layers. They suggest wearing an outer layer of a waterproof windbreaker material, which will act as a buffer against the wind. Next to the skin workers should wear a light, airy, dry shirt. Some experts say that it is important to have ventilation in the cloth next to the skin so the body can sweat freely. Frostbite tends to attack extremities first, so be sure to protect hands, fingers, feet, ears and nose from the cold.

In hot environments, it is important to ensure that clothing keeps workers cool and prevents dehydration. Experts suggest clothing that is light in color and fabric, and fits loosely to allow sweat to evaporate. Natural woven fabrics help assist in the evaporation of sweat. Wide-brimmed attachments on helmets or hard hats can be effective in deflecting direct sunlight away from the head.

Also important is the need for clean clothes. Dirty clothes, especially when they are next to the skin, do not insulate well and do not allow sweat to evaporate, according to the U.S. Army.

Some industries are turning to cooling vests to help prevent heat stress. Cooling vests can absorb the extra body heat, keeping workers' internal temperatures within a safe range.

Studies by the U.S. Navy have shown that crewmen using safety vests can safely work in hot environments for twice as long as those without them. The workers wearing the vest showed no thermal strain, the studies found.

There are two basic types of cooling vests on the market: passive and active.

Passive devices generally involve water-based or liquid chemical solutions packaged in sealed sectional plastic strips that can move with a worker. Once frozen, the packs are inserted into insulated vests. Frozen strips and gel packs generally last for two to eight hours before they need to be replaced, according to Sandra Steele, president of cooling vest manufacturer Steele Inc. of Kingston, Wash.

Vests containing chemical solutions are generally designed to maintain a constant temperature to help cool the worker. Ice pack-based products, on the other hand, change temperature as the ice melts. For these kinds of vests, wear a protective layer such as a T-shirt or cut-off sweatshirt under the cooling vest, recommended Chris Kairys, manager of strategic communications for MSA, Pittsburgh.

The most common active cooling device circulates cool water over the body using a power-generated pump. "All it is really is long underwear with a bunch of tubes in it," Kairys said. The tubes carry chilled water through the vest and recirculate water warmed by the body to an ice water reservoir where it is recooled.

Another version pushes compressed air through vortex tubes that separate hot air from cold air, and make sure that the cold air is spread over the body.

Dealing with temperature extremes due to weather or working conditions does not mean every environment has to feel like room temperature. However, the proper protection helps make most environments more tolerable, which is essential for worker protection and productivity.

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