Safeguarding against heat hazards.

Heat stress occurs when the body cannot release heat and cool itself. When the air temperature is as warm as or warmer than a person's skin, blood brought to the skin's surface cannot efficiently release heat. Working hard in high heat impedes the body's ability to cool itself because the muscles need extra blood, thus decreasing the amount of blood available to circulate to the skin and internal organs. Alertness, stamina, and productivity suffer; the body's core temperature and heart rate rise.