Page 208 - Safety Memo

Administrative Controls

There are many times when engineering and other controls are not practical, and administrative
controls must be instituted for worker protection. One administrative control is limiting the work
time by prescribing a stay time based on the work, environment, and clothing requirements. Stay
times are generally selected to be conservative because they are (1) based on approximations of the
heat stress and (2) designed to protect most workers. As a result, most workers can work beyond the
stay time, and some workers can go much longer.

Auxiliary Body Cooling and Protective Clothing
Auxiliary cooling systems can range from such simple approaches as an ice vest, pre-frozen and worn
under the clothing, to more complex systems; however, cost of logistics and maintenance are
considerations of varying magnitude in all of these systems. Four auxiliary cooling systems are
presently available: (1) water-cooled garments, such as water-cooled vest, undergarments, hoods,
etc., all of which require a circulating pump, liquid container, and battery; (2) air-cooled garments,
such as suits and hoods, generally require a vortex tube, connecting hose and a constant source of
compressed air; (3) ice packet vests, which although frozen when put on, do not provide continuous
and regulated cooling and require the use of backup frozen units every 2 to 3 hours; and (4) wetted
over-garments, which can be as simple as cotton terry cloth coveralls worn over the protective
clothing and wetted down with water. The wetted overgarment works best when there is air blowing
across the wet garment to increase evaporation.

Work Practices
Work practices, such as providing a period of acclimatization for new workers and those returning
from two weeks of absence, can help reduce the risks of heat disorders. Making plenty of drinking
water available at the workplace and urging workers to drink as much as possible both before going
into containment and after leaving containment is another method used to reduce heat stress. In high
heat stress environments, an employee can lose as much as one quart of liquid per hour. Wherever
possible, some type of product that has been formulated to replace the electrolytes and match the
weight of the body fluids lost by the sweating process should be used. This is necessary to enable the
body to quickly absorb replacement minerals.
Training supervisors to recognize and be able to correctly treat heat stress disorders is absolutely
essential. Prospective workers physical conditions should also be considered when determining their
fitness for working in a hot environment. Older workers, obese workers, and those workers taking
some type of medication are usually at a greater risk.

Acclimatization

Acclimatization to the heat through short exposures followed by longer periods of work in the hot
environment can reduce heat stress. New employees and workers returning from an absence of two
weeks or more should have a five-day period of acclimatization. This period should begin with a less
than normal workload and time exposure on the first day and gradually build up to normal workload
and exposure on the fifth day.

Work / Rest Regimen
Alternating work and rest periods with longer rest periods in a cool area can help workers avoid heat
strain. Supervisors must be trained to detect early signs of heat strain and should permit workers to
interrupt their work if they are extremely uncomfortable. If the interior temperature of the enclosure
cannot be reduced to a tolerable work level, it may be necessary to rotate workers. In addition to
work and rest, in an extremely hot environment, a daily weigh-in/out program should be initiated to

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