Document J3Be8Qy78e4MegE2jYG7Yz9Ev

INDUSTRIAL HYGIENE usually is not an important means of cool ing because the conductivity of clothing and the heat capacity of air are usually low Conduction and convection become an im portant means of heat loss when the body is in contact with a good cooling agent, such as water. For this reason, when people are exposed to cold water, they become chilled much more rapidly and effectively than when exposed to air at the same temperature. Air movement cools the body by conduc tion and convection, but, more importantly, moving air removes from about the body the film of saturated air which is formed very rapidly by evaporation of sweat and replaces it with a fresh layer which is capable of accepting more moisture Details of this type of thermal control are discussed in Chapter 28, "Local Exhaust Systems and General Comfort Ventilation " Effects of high temperature are counter acted by the body's attempt to beep the in ternal temperature down by increasing the rate of heart beat The capillaries in the skin then dilate to bring more blood to the surface so that both the rate of cooling and, gradually, the body temperature are in creased. If the thermal environment is tolerable, these measures will rather soon lead to an equilibrium where the heart rate and die body temperature remain constant. If this equilibrium Is not reached until the body temperature is about 102 deg F, correspond ing to a sweating rate of about 2 L per hr, there is imminent danger of heatstroke Heatstroke (also known as sunstroke) is not necessarily the result of exposure to the sun It is caused by exposure to an environ ment in which the body is unable to cool itself sufficiently As a result, the body tem perature nses, and reaches a point where the heat-regulating mechanism breaks down completely The body temperature then nses rapidly The symptoms are severe headache, visual disturbances, rapid temperature nse, and loss of consciousness The condition is rec ognizable by the flushed face and high tem perature The victim should be removed from the heat immediately and his body cooled as rapidly as possible, most readily by being wrapped in cool wet sheets Since the condition may be quickly fatal, medical help should be obtained as soon as possible Heat cramps may result from exposure to high temperature for a relatively long time, particularly if accompanied by heavy exer tion, with excessive loss of salt and moisture from the body Even if the moisture is replaced by dnnkmg plenty of water, the excessive loss of salt may provoke beat cramps or heat exhaustion Heat cramps are characterized by the cramping of the muscles of either the skele tal system or the intestines In either case the condition may be relieved m a few hours under proper treatment, although soreness may persist for several days. Heat Exhaustion is a shock-like state re sulting, like heat cramps, from the 2os of salt and moisture Its signs are a relatively low temperature, pallor, weak pulse, a feel ing of restlessness or anxiety, and uncon sciousness. Heat exhaustion is a more se vere condition than heat cramps and is oc casionally fatal A person with either condi tion, if conscious, should be given a half teaspoonful of salt m a half glassful of water every fifteen minutes for three or four doses, and put under medical care as soon as possible Prevention of heat exhaustion and heat cramps has become almost routine since the introduction of the use of salt tablets in the hot occupations There is some resistance to the use of salt tablets on the part of a few individuals who say that they are nauseated by them. Usually, nausea results when the tablets are taken with an inadequate amount of water so that an excessive concentration of salt is built up m the stomach To prevent nausea, a full 8-oz glass of water should be taken with each tablet It can also be prevented by the use of entenccoated tablets which do not dissolve until they have passed the stomach or by die use of tablets impregnated with cellulose which dissolve very slowly in the stomach contents Experience has shown that men do not stand a hot job very well at first, but de. velop tolerance rapidly and acquire full en durance in a week to a month Atmospheric pressure It has been recognized from the beginning of caisson work, about 1850, that men work ing under pressures greater than normal atmospheric are subject to various ills con nected with the job. The main effect (de- 39-11J