Document 1bK8GBxZgk2QyOLg3dGMZVpa

INDUSTRIAL HYGIENE as well as localized damage, can result from an exposure of sufficient intensity and time. In addition, flammable gases and vapors may ignite when they are inside metallic objects located in a microwave beam Power intensities for microwaves are grven m units of watts per sq cm. Areas having a power intensity of over 001 watt per sq cm should be avoided In such areas, dummy loads should be used to absorb the energy output while equipment is being op erated or tested. If a dummy load cannot be used, adjacent populated areas should be protected b> adequate shielding. Losers emit beams of coherent light of a smgie color or wavelength and frequency, m contrast to conventional light sources, which produce random, disordered light wave mixtures of various frequencies The laser (Light Amplification by Stimulated Emission of Radiation) is made up of light waves that are nearly parallel to each other, all traveling m the same direction Lightemittmg atoms are "pumped" full of energy and stimulated to fall to a lower energy level, giving oS light waves that are direct ed to produce the coherent laser beam The maser, die laser's predecessor, emits microwaves instead of light. Some compa nies call their lasers "optical masers " Pro posed uses for the laser include machining and cutting of metals, welding of micro scopic parts, and systems for higb-capaaty mmmimieAhrmf Since the laser is highly collimated (has a small divergence angle), it can have a large energy density in a narrow beam Di rect viewing of the laser should therefore be avoided The work area should contain no reflective surfaces (such as mirrors or highly polished furniture) for even a re flected laser beam can be hazardous. Suit able shielding to contain the laser beam should be provided Infrared radiation does not penetrate be low the superficial layer of the skin so that its only effect is to heat the skm and the tissues immediately below it Except for thermal burns, the health hazard is negli gible. Excessive exposure of the eyes to radia tion, mainly visible and infrared radiation, bom furnaces and similar hot bodies has been raid for many years to produce "glass blower's cataract" or "heat cataract" This condition is an opacity of the rear surface of the lens of the eye It was first reported among the hand blowers of glass in England m 1903 and became compensable m England m 1908 An investigation* conducted m an old plant producing boroalicate glass, where the heat exposure is much higher than it is m the production of the soft glasses on which heat cataract was first observed, failed to show any cases, although many of the em ployees have been exposed to the work for more than thirty years Although this investigation concerned only one company and too small a number of employees to be conclusive, the exposure was at least double that in the soft glass works from which the original reports were made, and the exposures of many of the workers had been long enough to throw a good deal of doubt on the production rf the condibon m the modem glass industry. This doubt should not, however, he per mitted to obscure the necessity for the pro vision of proper eye protection for men ex posed to high visible glare There is no doubt whatever that powerful visible glare can harm the eyes, as "eclipse blindness" demonstrates. Visible radiation and ultraviolet radiation also do not penetrate appreciably below the skm, their effects are essentially heating on the surface. The effects of the ultraviolet waves are much more violent than are those of the visible or infrared--a severe burn can be produced with no warning whatever. Since ultraviolet radiation in industry may be found around electric arcs, they should be shielded by materials opaque to the ultraviolet Opacity in the ultraviolet has no relation to opacity m the visible part of the spectrum Ordinary window glass, for instance, is almost completely opaque to die ultraviolet although transparent to the visible A piece of plastic dyed a deep ledviolet may be almost entirely opaque in the Dunn, Karl L. "Cataract from Infrared Rays (Glass Worker's Cataract)." Archives of Industrial Hygiene and Industrial Medi cine. 1-168-180 (February 1950). 39-16