Document OEMpve3OVeVNM90keDLpwyM11

1966 National Safety Congress cm be bad rather economically by passing the makeup air through an evaporative cooler. This is not mechanical refrigeration, as used in air conditioning, which is vastly more costly and requires recirculation of room air--an arrangement that cannot be permitted when air contaminants arc re leased in the workroom. Heat is probably the cause of more gen uine discomfort and complaint than any other environmental condition in industrial plants, and there arc several common mis conceptions about its control. A person's thermal comfort depends on four factors: air temperature, humidity, movement or velocity of air around him, and--the one most commonly misunderstood --presence of hot objects or surfaces sur rounding him. If these last arc at a tem perature of 95 or higher, heat will be radiated to the individual and will heat him up just as hot air docs. However, we can't usually tell just by the "feel" if it's hot air or radiant heat that's making us uncom fortable. This is why a simple instrument, the globe thermometer, assumes great im portance in evaluating industrial heat ex posures, but is far less widely used than it should be. Importance of radiant heat is that it is controlled in a totally different manner from what is used to drop the air temperature. Radiant heat is electromagnetic energy that docs no heating whatsoever until it strikes some object, like a person, where it is absorbed. No relief from it whatsoever results from blowing air around. The only protection is to set up an invisible infrared "shadow." This can be done by placing any kind of opaque shield or screen between the man and the radiating surface. Unless the screen itself, however, reflects radiant heat, it will absorb the energy, heat up and reradiate. Fortunately, commercial aluminum foil, aluminum sheets and corrugated alumi num siding arc all highly reflective in the infrared--and arc cheap. After locating the sources of radiant heat, shields placed be tween them and the employees will bring welcome relief. High level noise is an environmental con dition that has long been on the upturn, probably because each day we have more and faster machinery. Generally, noise is not the cause of complaints that heat is, but noise can cause irreversible damage to what some feel is the most precious of all our senses, hearing. Exposure to high noise over a period of years damages the nerve endings of the inner car, resulting in varying degrees of deafness which hearing aids cannot coun teract. High noise makes speech, the giving and hearing of instructions, and warning signals sometimes impossible. Finally, it may produce fatigue, annoyance, and other effects on the nervous system that arc no doubt real but as yet can't be measured. From the nurse's standpoint, everyone en tering on a job. in a nojsy plant, as well as those already working there, should be given an audiometric test of hearing as part of every complete physical examination. The testing area must be sufficiently quiet--most plant medical services arc not. This should be achieved by buying a commercial prefab audiometric testing booth. Such a booth is nearly always satisfactory, whereas a plantmade "sound proof" room invariably docs not lower the noise sufficiently and in the end costs more. The audiometer may be a manual one for giving air-conduction tests only (bone con duction and masking arc not used). How ever, the nurse's time will be saved, and a permanent graphic record will be obtained which is independent of the common vari ations in testing technics of different op erators, if a self-administering, or automatic, audiometer is acquired when the program is inaugurated. Audiograms should be given on job transfers, and on terminations either for job change or. retirement. There is a parallel between control of noise and control of air-borne dust: the noise may be lowered by a change in its source (for example, replacing a fan with excessively high tip speed by one of low tip speed); the source may be enclosed with a box or enclosure of high noise attenu ation; isolation of the source may be ac complished by time (shortening the exposure period) or distance (sometimes with sound absorbing baffles hung from the ceiling to reduce spread of noise elsewhere in the room); or by personal protective equipment in the form of car plugs or muffs. When any occupational health hazard can not be brought under control, personal pro tective equipment must be relied on. But this must always be regarded as a last re- 148