Document Moa6z5dbjg1o2nGQgXN2zMk57

788 S. K. GUTH AND E. A. LINSDAY there is a measurable period of time between exposure and development of injurji deep burns may be endured without immediate discomfort. The severity of t burn depends upon the spectral distribution of energy in the ultraviolet region the intensity, and the time of exposure. Certain wave lengths are more effecti in producing discomfort and injury than others. Figure 41 illustrates the relati effectiveness of various wave lengths in producing erythema. i Figure 41. The selective effectiveness of various wave lengths in producing erythema.| Considerable discomfort can be produced in the eye by exposure to radia below..about 3100 A. The absorption of this radiation by the outer layers eye (cornea and conjunctiva) produces conjunctivitis, which occurs 4 to f after exposure and may last several days. While conjunctivitis itself is ijj|i serious, great care should be taken to avoid secondary infection. Protective glasses should be worn by all personnel when they may be exp to erythemally effective radiation. Furthermore, opaque shielding should ' around welding areas to protect other persons. It has been suggested87 that 0.5 microwatt per square centimeter permissible amount of ultraviolet for a 7-hour continuous exposure or 0.1 watt per square centimeter for 24 hours. " Council on Physical Therapy, J. Am. Med. Assoc., 122, 503 (1943). vti" CHAPTER XXI Heat Control in the Hot Industries T. F. HATCH This chapter is concerned with the protection of workers in the so-called hot industries where heat exposures are increased substantially above the normal levels fixed by the local climate because of the extra heat added to the environment by the hot processes. Industrial heat exposures may be classified as either? hot-dry or warm-moist. (1) In the hot-dry industries, such as steel mills, forge shops, and glass manufacturing plants, the thermal load on the worker is increased by the sensible heat that escapes from the process equipment into the surrounding work (space. The major component is radiant heat from the surfaces of tanks; hot metals, and the like; the heat-load contributed by the surrounding hot air is secondary. 1 s-vNo moisture is added to the air so that there is no loss in the evaporative cooling Vf^capacity of the atmosphere. The requirements for sweating and evaporation, are ^increased, however, because of the added radiant and convective loads. For men a^xposed^(rsuchn3m'dititm-s7-hMrh^lSffc:d',.iTmamtamFa^ The ey^p'orktibn of .* psweat. (Z) In the warm^moist industries, such' as laundries, dye houses, and deep ^mines with extensive use of water for dust" control, water,vapor ,is added to the t!air from wet processes or as escaping steam. Relatively little*sensib]e heat,escapes, 3|but evaporative cooling capacity is greatly reduced. In"6tequence, th$ worker '`jSSmay be unable to dispose of his metabolic heat plus the,.small additional heat ^gained from the environment. AS, . fj. The amount of heat or-water vapor added to the environment in the hot in dustries is usually substantial so that it is not economically feasible to provide insufficient cooling of, the air to offset completely the added-thermal load;- Thus, the tSfP^rt standards that hgye b^en. es1^1;l|she^,.{pjc. ^ned-offices-and-Irght^ljdnstrfegr-(gifa^tgrv\Hli) 'doTi,6thecess'ariiyrapply'"tb"the` design of heat-control measures for the hot industries. Different standards, above the' limits of simple-comfort, are required and these will vary in respect, to,,,the physiological and psychological criteria on which They are based^feft^Wtijpbn at>bkmd-ofrindustEyta>nd=thejnatuxteofthe'WorkrThe level-of-heat^exnbSnrRWfptatffhR , within safe limits to prevent serious physiological disturbance-or, injury-to `health. It will be necessary to go further toward the comfort zone'-in `certsJin in,., dustries where impairment of efficiency and other physiological disturbances,inter- i