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604 CHAPTER 33 1948 Guide emanating from, animals and people, some of the gaseous constituents of combustion, alcohols, ketones, esters, and , gaseous products of .putre faction. The selective action of charcoal with admixture of water vapor and organic gases is shown in Fig. 4. ,- Charcoals differ widely in their adsorptive capacity; Those which have marked adsorption characteristics, such as properly, prepared coconut shell charcoals, are sometimes c^led activated charcoals or activated carbon. These materials can adsorb approximately 50 per cent of their own weight of many, organic gases at 70 F. The charcoal may be used for a long time by reactivation at high temperatures, under which condition it gives up the adsorbed gases. Temperatures of approximately 1000 F are desirable for reactivation. Charcoals for use in air handling systems should be able to stand physical handling, including reactivation, without excessive loss by breakage or dusting. As applied in air handling systems, the charcoaj is placed in perforated metal containers which are grouped in frames and set in the air stream. The percentage removal of an organic gas, such as carbon tetrachloride, is 95 per cent or above when placed in intimate contact with the carbon at 70 F. In commercial apparatus there may be' a by-pass effect which depends on the physical arrangement of the charcoal containers. This by-passing reduces the percentage removed in the total gas passing through the adsorber. Resistance to air flow is usually selected within the general range of resistance of impingement filters.- The required quantity of recirculated air to be treated is determined by the requirements for contaminant-free air, minus the' outdoor air, divided by the fraction denoting the percentage removal of the gas in question in the adsorber bank which is to be used. Adsorbers may be applied to reduce objectionable gases entering .through the outdoor air inlet. They may also be used to reduce the odors caused by exhausts from processing. Adsorber beds, in all cases, should be protected from dust, free oil and grease. Air Cleaning Devices 60S REFERENCES: *--Bronchial Asthma and Allied Allergic Disorders, by S. S. Leopold and C. S. Leopold ([Journal of the American Medical Association, March 7, 1925, Vol. 84, p. 731-734). 2--Dirt Patterns on Walls, by R. A.' Nielsen (A.S.H.V.E. Transactions, Vol. 46, 1941, p. 247). 3--industrial Dust, by Philip Drinker and Theodore Hatch (McGraw-Hill Co., New York, N. Y.). 4-- A.S.H.V.E. Standard Code for Testing and Rating Air Cleaning Devices Used-in General Ventilation Work (A.S.H.V.E. Transactions, Vol. 39. 1933, p. 225). s--a Test Method for Air Filters, by Richard S. Dill (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 379). ^ BIBLIOGRAPHY Design and Application of Oil-Coated Air Filttts, by H. C. Murphy (A.S.H.V.E. Transactions, Vol.. 33, 1927, p. 73). Operation and Maintenance of Air Filters, by W. G. Frank {Healing, Piping and Air Conditioning, May. 1931, p. 378). and Characteristics of Air-Borne Impurities, by W. G. Frank {Heating, Piping and Air Conditioning, January, 1932, p. 35). Fundamental Principles in the Design of Dry Air Filters, by Otto Wechsberg (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, April, 1933, p. 217). ` The Economic Factors in Converting Recirculated Air for Ventilation, by H. E. Ziel and Henry Sleik (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, July, 1943, p. 367). Operation, Maintenance of Cloth-Screened Dust Collectors, by W. F. Terry {Heating, Piping and Air Conditioning, May, p. 259, June, p. 304, 1933). Testing and Rating of Air Cleaning Devices Used in General Ventilation Work, by Samuel R. Lewis (A.S.H.V.E. Transactions, Vol. 39, 1933, p. 277). A.S.H.V.E. Research Report No. 1094--Air Filter Performance as Affected by Kind of Dust, Rate of Dust Feed, and Air Velocity Through Filter, by F. B. Rowley and R. C. Jordan (A.S.H.V.E. Trans actions, Vol. 44, 1938, p. 415). A.S.H.V.E. Research ReportNo. 1122--Air Filter Performance as Affected by Low Rate of Dust Feed, Various Types of Carbon, and,Dust Particle Size and Density, by F. B. Rowley and-R. C. Jordan, (A.S.H.V.E. Transactions, Vol. 45, 1939, p. 339). \ A.S.H.V.E. Research ReportNo. 1145--The Effect of Lint on Air Filter Performance, by'F. B. Rowley and R; C. Jordan (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 25). A.S.H.V.E. Research Report No. 1169^-Comparison of the Weight, Particle Count.and Discoloration Methods of Testing Air Filters, by F. B. Rowley and R. C. Jordan (A.S.H.V.E. Transactions, VoL 47, 1941. p. 29). A.S.H.V.E. Research Report No. 1187--Economical Air Velocities for Mechanical Air Filtration, by F. B. Rowley and R. C. Jordan (A.S.H.V.E. Transactions, Vol. 47. 1941, p. 391). A.SH.V.E. Research Report No. 1218--Overloading of Viscous Air.Filters During Accelerated Tests, by F. B. Rowley and R. C. Jordan'(A.S.H.V.E. Transactions, Vol. 48, 1942, p. 437). ,.. The Dust-Free Space Surrounding Hot Bodies, by H. H. Watson {Transactions of.the Faraday Society, Vol. 32, 1936. Pt. 2, p.1073). ` A New Electrostatic Precipitator, by G. W. Penney {Electrical Engineering. January, 1937, p. 159). ' Electrostatic Precipitation for Aircraft, by Howard E. Corbitt and Norman J. Clark {Aero Digest, December, 1940, p. 132). Cleaning of Air and Gas by Thermal Repulsion, by Samuel C. Blacktin {Journal Society of Chemical Industry, 68, 1939, p. 334-8, 69, 1940,p. 153-4). . ... Pointers on Selecting Equipment for Industrial Gas Cleaning, by C. E. Miller {Chemical and Metal lurgical Engineering, 46, March, 1938, p. 132-5). . Electrical Precipitation, by W. A-. Schmidt and E. Anderson {Electrical Engineering, 57, 'August, i938, p. 332-338). .. Electrostatic Precipitation for'Cleaning Industrial Gases, by H. W. Wagner {Fuel'Economist, 10-, 1935, p. 895-9, 942-5, 971-3). Dust Precipitation, by M. Pauthenier and Mme. Moreau-Hanot {Electrician, US, August 10, 1934, p. 187-9). Alternating Current Precipitators for Sanitary Air Analysis: II. Add Formation in EldAnc Predpitators, by W. G. Hazard and Tomoyoshi Ishikawa {Journal of Industrial Hygiene, October, 1932, p. 367-70).. Electrical Predpitation, by A. W. Simon and L. C. Kron {Electrical Engineering, 61, February, 1932, p. 93-5). The Mathematical Theory of the Cottrell Electric Predpitator, by A. W. Simon {Iron and Steel Engi neering, 6, 1929, p. 143-6). Progress in the Art of Elertrical Predpitation Since 1900, by P. E. Landolt {Transactions American Electrodiem. Society, 61, 1927). Some Factors and Prindples Involved in the Separation and Collection of Dust, Mist and Fume from Gases, by Evald Anderson {Transactions American Institute of Chemical Engineers, 16, 1924, Pt. 1, p. 69-86). Electrical Predpitation of Solids from Smelter Gases, by Ross B. Rathbun {Transactions American Institute of Electrical Engineers, 41, 1922, p. 815). Electrical Engineering Features of the Electrical Predpitation Process, by G. H. Horne {Transactions American Institute of Electrical Engineers, 41, 1922, p. 808).