Document JNQyKNv5jQ4mm7yNbOnBDYxMv

346 FRANK A. PATTY i;(| preferable in that it 'has a longer life and provides more economical prpt The useful life of the universal, type N, canister is limited by the lif| drying agents used to protect the catalyst from moisture (2 to 6 hours* 1 diagrams a typical type N canister. The continued use of a partially exf Attachment tor onion to gas mask Figure 1. A type N canister. (Courtesy Bureau of Mines, U. S. Department of Lhe'.Ini^ __ canister may be permissible in gases or vapors having distinct warning-1'c^r iatics, provided it is used near an uncontaminated area so that the wfl. reach safety quickly after detecting leakage, because the end of the is not sharp, but rather gradual. Any used canister should always tilff with a new one before the mask is used in an unusually hazardous situaf RESPIRATORS AND RESPIRATORY DEVICES 347 ` 2. Chemical Cartridge Respirators I" .gffgmical cartridge respirators usually consist of a small canister attached l^^^'half-mask facepiece. The fills are similar to those used in gas masks, pplplthese respirators may be considered miniature gas masks. Filters for w^glarticulate matter may be incorporated. These respirators are designed |TMlc>ngi?d use in light exposures where workmen could work without proteciibii'iAv. here prolonged daily exposures might prove harmful to health. The ^jriuimiiconcentration of gases or vapors for which such devices are approved "Wpjrh., 0.1 per cent by volume. Only a relatively few chemical cartridge Ijuirs-iinve been granted approval certificates, and the protection afforded by g^^Bnapproved articles is open to question. Recently, cartridge respirators J~ mproved for use against solvent vapors.. A word of caution should be ver, that these do not protect against lead mists, often associated with ||fj|||jjiDor8 in paint spraying. Where lead mists are involved no cartridge I'l-ratur^is approved, nor should any be depended upon; until further advances llome air-supplying device is required. Respirators approved for Mad mists as well as solvent vapors and mists have not yet appeared. fchanical Filter Respirators {for Dust, Fume, Fog, or Mist) leiijiajiical filter respirators usually consist of a fibrous filter, such as felt or ulljjrted cellulose fiber paper, secured in a holder and connected directly ^f^irfask-facepiecer-The-filterJs-a_maze_Qf. fine,. QlosebLpacked fibers that Skufgpvbrk of microscopic passages. When air is drawn through this maze, of the suspended dust, fume, mist, and fog is removed by physical Kn;un|jfer,hc=e filters are approved for various uses, but not all of them are n't* ts*v w-iV?* BViV'lfeir^sinaller particle size, require a finer mesh filter.' Fumes, it must be ''^L^are-particulate matter formed by volatilization and condensation, as with use or plugging. Increased breathing resistance is the filter's life. These devices are intended for-pj:olpnged use szffifirc, fa~r,c 'light,in weight and compact. They do not seriously interfere with l7M5[jjlffiirvjduties. To say that they are comfortable is stretching the imagina- optrol by other means is feasible, control by personal respiratory method of Choice. Rather, mechanical-filter respirators are .either temporary or last-Tesort measures; but they certainly 'rl mended for any workman who is obliged to work in an atmosphere " ShS? :- MM