Document DROB3KmY3O7Ybakrrgr7q3Bn

578 JBVING HARTMANN Sometimes it is also possible to make use of high atmospheric humidity 'ifj the equipment or room containing flammable dust. It may reduce somewhat till ease of dispersion and might make ignition slightly more difficult. As a rule, hotj ever, reliance on this practice or on the effect of a small amount of moisture in du| is not recommended, because the dust still can he thrown into suspension afi ignited by a strong source of ignition. The usefulness of high humidity lie! chiefly in preventing or reducing the accumulation of static electricity on the dusTM 7. With respect to fire prevention and fire extinguishing in flammable dustf in addition to the usual recommendations for fire prevention, the following point! should be noted: (a) Attention should be directed to the hazard of possible spoi|l taneous heating in many powdered products, particularly after grinding. (fil Efforts should be made to detect and eliminate smoldering particles in dust dpi posits, especially before periods of plant shutdown, (c) First-aid protective equipff ment should be installed that is suitable for fires in combustible dusts, such all small hose, water pails, soda-acid extinguishers, and hand-operated water pump! tanks. A small hose equipped with a spray-type nozzle is satisfactory for mora Ifdusts. The fine spray wets the dust and is not as apt to produce a dust cloud as a solid stream, (d) Large hose streams of fire-department sizes should be use:ffi only with great caution where combustible dusts are involved, because dust migp be thrown into suspension by their use, with a consequent explosion. Plant errif ployees and the fire department should be advised of this danger in advance ?c trouble, (e) Spray or fog nozzles can be used without danger of disturbing dujj deposits, and nozzles of this type should be available with all hose used for fire! protection where combustible dust is present. (/) Small fires in magnesium, minum or other metal powders are best extinguished by sand, talc, soapstone, other dry inert materials applied gently to surround and smother the fire, or' 3 some circumstances by the use of such materials as hard pitch, which comple seal the powder from the air.22 " H. R. Brown, I. Hartmann, and J. Nagy, U. S. Bur. Mines Rept. Invest. No. 3672, : CHAPTER XVII Physiological Effects of Abnormal Atmospheric Pressure* HEINZ SPECHT I. Introduction--Historical Background The effects of the pressure exerted by the atmosphere upon the body, lespecially those that follow changes in this pressure, for convenience are con sidered in two classes, linked by the common physical attributes of gases. They jfcomprise those found (I) in the range from normal barometric pressure to positive pressures met in diving and caisson work and (S) in the range from pdrmal to the reduced pressures incident to ascent into the atmosphere, respec tively. As will be seen subsequently, certain details of the response to these two alterations in atmospheric pressures are different and necessitate separate dis cussion. In general, however, there is a continuity of response that has permitted feiirataa'l_ffjrceleration"bfTmderstanding'of-problems-arising-in these -fields. Historically, the elucidation of essential factors under both conditions rests flh observation and practices of long standing, on the one hand in the diving Kndustry, and on the other hand in agriculture and mining in mountainous areas, thich have been implemented from ancient times by special knowledge, uncritical Sough it may seem in the light of more recent observation and experiment. W It iB probable that peafl and sponge diving offered-the earliest and most Ifrequent industrial encountering of effects of compressed air. It seems likely that fno realization of the physiological aspects existed until the time of Aristotle,1 and Ithen only to the extent that he wrote of the practicality of inverting a.kettle of Ifir over the head as an aid in prolonging diving operations. Roger Bacon is jrtefi to'have:invented -a~diving-bell-aboutT250 A.D.^ -it-was bot-until the The author wishes to acknowledge the helpful criticism of the text by Dr. J. N. Stan dard, Lt. U. S. N. R, Research Division, Bureau of Medicine and Surgery, Washington, D. C., St. W. J. Bowen and Dr. H. L. Andrews of the Industrial Hygiene Research -Laboratory, Noffional . Institutes of ..Health,. Bethesda,. Maryland, Much helpful discussion on .controversial jS|>ihts waB carrieH-on witHTEKTsfaT^thVTtviStion^^ihiBr-XJinrdFtire'indastrteFHygiene ISesearch Laboratory, National Institutes of Health. *R. Heller, W. Mager, and H. Schrotter, Lujidruckerkrankungen mit besonderen Ruck-., chtigung der sogennanten Caissonkrankheit, Vol. I. Holder, Vienna, 1900. `Heller et al., op. cit., Vol. II. 679