As summer continues to keep its grip on most of the U.S.,
roofing contractors and workers must be increasingly vigilant to
avoid health problems caused by high temperatures. Two heat-induced
disorders of significant concern are heat exhaustion and heat
To keep internal temperature in a safe range, the human body
rids itself of excess heat through evaporation and radiation.
During evaporation, the sweat glands move water to the skin's
surface to be cooled by surrounding air, reducing the internal body
temperature. Heat is dissipated by radiation when the heart pumps
more blood; blood vessels near the skin surface expand, bringing
more blood to the surface to be cooled by surrounding air.
These mechanisms can be stressed and possibly rendered
ineffective during hot, humid weather conditions. When humidity is
high, sweat does not evaporate and cool the body. Similarly, if the
outside temperature is high, no heat transfer occurs as the body
continues to move more blood to the skin surface in an effort to
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