Document qOmMYQO1mMKk3ByM9ybvbZXR

146 Turcnty-fifth National Safety Cotigress Droplets of mill arc mcrtnrilv micro scopic in sice or they would .sot retnain m suspension. At soon as several drop* lets collide and form a Urge drop Ike li quid settles out. Therefore, it is possi ble to dispel a true mist very readily by snntily slirrine up the air--ventilation or dilution ts unnecessary. Mist droplets can be filtered out by or dinary dust respirators--that is. the visi ble Ionian of a fog is easily removed by filtration--but the gaseous* constituent mar pass through the filter. If the mitt happens to he eorrosive to fabrics the re sultant effect upon a dust respirator is bad. Paint spraying' generates a mist and a certain amount of vapor. Protec tion usually consists of an air-line res pirator but it is not at all uncommon to use cartridge respirators containing acti vated charcoal and a filter. A gas contains no solid or liquid partides under ordinary atmospheric condi tions. The filter units of any of the common makes of respirators are inef fective against gases. Respiratory pro- lectin equipment which catches gases al ways consuls in some chemical agent which cither absorbs the gas or converts it into some other substance which can be absorbed. Because one can rarely be sure of the gas concentration to be en countered it is common practice in ex ploring man holes, for instance, to use devices supplied with air or oxygen in order that the wearer may be safe, re gardless of the conditions he finds. The gas mask, however, and its outgrowth, the chemical cartridge respirator have a definite plaee in industry and are in wide use today. The U. S. Bureau of Mines has helped in the manufacture and use of respiratory protective equipment greatly by its issu ance of specifications for permissible equipment. Their present schedules do not include the air-supplied respirators such as those used in paint spraying or sand blasting but both the Bureau and the American Standards Association will issue such specifications presently. Discussion following the address was based on these points: 1. What protection is provided against a dangerous accumulation of air pressure in the ordinary fresh air hose mask? The helmet is not rigid. Air trill leak out long before a dangerous pressure ac cumulates. or a safety link, provided in some types of hose mask, will blow out. 2. Would a protective mask approved for lead dusts fiber out sine .vide? Yes. However, almost any type of mask will filler out xinc oxide, since these particle* arc easily trapped. S. Will the simple face mask filter out ordinary smoke or will it absorb it? ' ft Is impossible to answer such a ques tion. There are as many types of ordinary masks as there are ordinary dusts. A mask must be purchased to fit a specific need. This is not difficult, however, since all types are available. Glass Used for the Protection of the Eyes Against Injurious Radiation By k d. tillyer Sonthbridge, Uu The effect of excess visible light on the eye is immediately felt. If there is tou rourh. anyone except the sun gazers Im mediately turns away, doses the eyes or seeks some kind of relief. There is a tendency to use too dark glasses in weld ing. inherited from the days when even the blackest glasses gave practically no protection from the insidious invisible radiations. A proper rule is. use a shade number which gives good, immediately comfortable vision and insist that this glass give protection against the invisible radiations. The effects of the ultra-violet and the infra-red radiations are not as quickly noticed as the risible. We cannot say* as we said for the visible, "get good im mediately comfortable vision" because the first noticed effect of the ultra-violet oc Safety Equipment 147 curs several hours after the exposure and the infra-red effect is usually longer de layed. One outstanding piece of research was that of Sir Ww. Crookes on glasses to protect the eyes of glass workers. From statistical data. Crookes arrived at the conclusion that the ultra-violet and/or the mfra-red produced cataract in the human eye. This was important, but the real importance of his research was that he found that the infra-red was absorbed by iron in the ferrous state in ordinary glass. Also, he found that a cerium compound when added to glass was an excellent absorber of the ultra-violet. These two discoveries were important fat the manu facture of good absorbing glasses, al though full advantage was not taken im mediately because Crookes found no ultra-violet, but only infra-red. present In the radiations to which glass blowers were subjected during their working hours. These last fonr words should be underlined from the indications of mod ern research. A very important paper was published by Von der Hocvc of Leyden in 1920 which showed the tendency of ultra-violet to produce other cataract or macular de generation. Macular degeneration has not been considered as frequently as cata ract in the literature. Probably it occurs more frequently after the removal of the crystalline lens in the cataract operation. The crystalline lens is in many cases, although not always, an effective screen cutting out ultra-violet. Dr. Janet Clark has published an out standing research paper which appears to tie together both ultra-violet and infra red m its more serious forms of injury to the human eye. that is, cataract. She says: "The initial process of light dcnaturation may therefore occur in the lens without any risible opacity, and it is prob able that there is always some denatured protein present as the result of exposure to sunlight." . . . "The second step in tight coagulation by proteins Is very much accelerated by heat and occurs rap idly at 40* C <10f" F.) . . . It is prob able therefore that the higher incidence of cataract in workers exposed to moften glass and metals ts due to an increased *Msny elher condition* ouy predme eatirsct beside* arcssire radiation* rate of precipitation of light denatured protein when the lent is heated above body temperature by exposure ' to large sources of radiant heat, and when low concentrations of calcium or other sub stances producing a similar effect are present** We always have some ultra-violet in untighL In welding, especially arc weld ing, we have extremely intense ultra violet Add to this the infra-red from hot metal or "radiant heat" and combine this with a very slight excess of calcium and we have the necessary and sufficient conditions to produce cataract* We have considered the more serious results of radiations. The less serious, although extremely uncomfortable at times, are more often experienced. The most common Is "sand in your eyes.** from ultra-violet falling on the conjunc tiva. This is not comfortable to say the least and frequently is caused by reflec tions from the original source reaching the side of the eyeball. Some white punts do not reflect the nltra-riolet while others do. One of the best reflectors is an oxi dized aluminum surface, one of the poor est is a highly polished silver surface, quite different from the way these mate rials refleet visible radiation. The first felt action of infra-red on the eyes varies among different fasdhrMaala and with different regions of the infra red. The long wave infra-red (longer than about 13) is absorbed by the water in the tears or the conjunctiva at the very surface of the eyeball, since water is ex tremely opaque to these radiations. Shorter wavelength radiations than this, but longer than the visible waves, pene trate deeper and deeper into the eye. The simplest way to avoid the different types of eye troubles so produced Is Co elimi nate both types of infra-red radiations. The early glasses used for protection were a delusion and a snare. The visible was reduced so much that the work could not be seen, in the hope that the eye would be protected. Sometimes the ultra violet would be eliminated, sometimes not. The infra-red was usually well trans mitted. about as well as with two or three layers of ordinary window glass. The infra-red was another matter, rarely being reduced much by accident. Only two eases do I remember, one an