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Human bodies dissipate heat in one of three ways: by <br />varying the rate and depth of blood circulation; by losing <br />water through the skin and sweat glands; and by <br />panting. As the blood is heated to above 98.6°F, the <br />heart begins to pump more blood, blood vessels dilate <br />to accommodate the increased flow, and the bundles of <br />tiny capillaries penetrating through the upper layers of <br />skin are put into operation. The body's blood is <br />circulated closer to the surface, and excess heat is <br />released into the cooler atmosphere. At the same time, <br />water diffuses through the skin as perspiration. The skin <br />handles about 90% of the body's heat dissipating <br />function (Darling). <br />Heat disorders generally have to do with a reduction or <br />collapse of the body's ability to cool itself by circulatory <br />changes and sweating, or a chemical (salt) imbalance <br />caused by too much sweating. When the body cannot <br />cool itself, or when it cannot compensate for fluids and <br />salt lost through perspiration, the temperature of the <br />body's inner core begins to rise and heat -related illness <br />may develop. Studies indicate that, other things being <br />equal, the severity of heat disorders tends to increase <br />with age. Heat cramps in a 17 -year-old may be heat <br />exhaustion in someone 40 and heat stroke in a person <br />over 60 (Darling). <br />When the temperature gets extremely high, the National <br />Weather Service has increased its efforts to alert the <br />general public as well as the appropriate authorities by <br />issuing Special Weather Statements. Residents should <br />heed these warnings to prevent heat related medical <br />complications. As a result of the latest research <br />findings, the National Weather Service has devised the <br />"Heat Index" (HI). The HI, given in degrees Fahrenheit, <br />is an accurate measure of how hot it really feels when <br />relative humidity is added to the actual air temperature. <br />The National Weather Service will initiate alert <br />procedures when the HI is expected to exceed 105EF <br />for a least two consecutive days. Possible heat <br />disorders related to the corresponding HI are listed <br />below (Darling). <br />Indian River County Comprehensive Emergency Management Plan Basic Page 17 <br />