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ITT )| !! 4ifii. . sr I ? t 1 t, i I ( 164 CHAPTER 8 1950 Guide Table 6. Approximate Limits of Flammability of Singlb Gases and Vapors In Air at Ordinary Temperatures and Pressures* Gas ob Vapor Lowes Limit Per cent bt VoLUMB Upfbb Limit Per cent bt Volume Closed Cup Flash Point F Daob Acetaldehyde....... Acetone................. Acetylene.............. AllyLi-alcohol........ Ammonia.......... Amyl alcohol-- Amyl chloride... Amylene................ Benzene (benzol) Benzyl chloride.. Butane............ Butyl acetate. Butyl alcohol. Carbon monoxide.................. Crotonaldehyde...................... Cyclohexane............................ Cyclopropane.......................... Decane...................................... Dichloroethylene (1,2).... Diethyl selenide.................... Diox&ne.................................... Ethane...................................... Ether (diethyl).................... . Ethyl acetate.......................... Ethyl alcohol......................... Ethyl bromide....................... Ethyl celloeolve..................... Ethyl chloride..................... Ethylene.................................. Ethylene dichloride............. Ethyl formate....................... Ethyl nitrite........................... Ethylene oxide..!................ Furfural (125 C)................... Gasoline (variable).............. Heptane................................. Hexane.................................... Hydrogen cyanide................ Hydrogen............................... Hydrogen sulfide................. Illuminating gas (coal gas) Isobutyl alcohol................... Isopentane............................. Isopropyl acetate................. Isopropyl alcohol.................. Methane................................. Methyl acetate..................... Methyl alcohol..................... Methyl bromide................... Methyl butyl ketone.......... Methyl chloride.................... Methyl cyclohexane............ Methyl ethyl ether.............. Methyl ethyl ketone........... Methyl formate..................... Methyl propyl ketone........ Natural gas (variable)........ Naphtha (benzine).............. Naphthalene............... ......... Nonane................................... Octane..................................... Paraldehyde.......................... Pentane.................................. 4.0 2.5 2.5 2.5 15.5 1.2 1.6 1.6 1.3 1.1 1.8 1.4 1.7 2.0 1.2 12.5 2.1 1.3 2.4 0.67 9.7 2.6 2.0 3.1 1:8 2.2 3.3 6.7 2.6 4.0 2.7 6.2 2.7 3.0 3.0 2.1 1.4-1.5 1.0 1.2 5.6 4.0 4.3 5.3 1.7 1.3 1.8 2.0 6.0 3.1 6.7 13.5 1.2 8.2 1.1 2.0 1.8 6.0 1.5 4.3 . 1.1 0.9 0.83 0.95 1.3 1.4 57 12.8 80 26.6 7.7 6.8 8.4 15.0 9.7 50 74.2 15.5 8.4 10.5 2.6 12.8 22.2 12.6 36.5 11.6 19.0 11.3 15.7 14.8 28.6 15.9 16.5 50 80 7.4-7.6 6.0 6.9 40.0 74.2 45.5 33.0 7.8 i6.0 15.5 36.6 14.5 8.0 18.7 io.i 9.5 22.7 8.2 13.6 6.0 2.9 3.2 7.8 -17 0 70 100 i2 140 84 -22 55 1 iis 67 54 -49 28 54 io4 --58 66 -4 -31 140 -50 25 -15 - 82 43 53 14 52 25 -35 30 -2 20^-iio 176 88 56 Air Contaminants 165 Table 6 Approximate Limits of Flammability of Singlb Gases and Vapors 1 In Air at Ordinary Temperatures and Pressures" (Concluded) Gas ob Vapor Lower Limit Per cent bt Volume Ufpeb Limit Peb centbt Volume Closed Cup FlashPoint F Deo5 . -t TuijMutino ... . . . . / * tt.N ..................................... 2.1 1.8 2.1 2.0 3.4 2.0 1.8 1.3 0.8 1.7 4.0 6.0 1.0 10.1 8.0 13.5 11.1 14.5 22.0 12.4 7.0 27.6 21.7 - 70 6.0 58 59 66 74 40 95 63 * Adapted from: Fire and Explosion Hazards of Combustible Gases and Vapors, by G. W. Jones; Chapter 13 Industrial Hygiene and Toxicology, edited by F. A. Patty, (Interscience Publishers, 1948); Properties of Flammable Liquids, Gases and Solids (Associated) Factory Mutual Fire Ins. Cos., January (1940); and National Fire Codes for Flammable Liquids, Gases, Chemicals and Explosives--1945 (National Fire Protec tion^ Association). .... . . , , . ... b Closed cup refers to the equipment used in flash point determinations. of air. Maximum pressures generated have been reported as high as 500 psi, although they are more likely to be of the order of 50 psi. Investiga tions on the flammable characteristics of dusts are currently made at 0.1 and 0.5 oz per cubic foot.16-21 ATMOSPHERIC POLLEN Properties of pollen grains discharged by weeds, grasses and trees and responsible for hay fever are of special interest to designers of air cleaning equipment (see Allergic Disorders in Chapter 7, and Air Cleaning, Chap ter 33). Whole grains and fragments transported by the air range chiefly between 10 and 50 microns in size, but some have been measured as small as 5 microns, and others over 100 microns in diameter. Ragweed pollen grains are fairly uniform in size within the range of 15 to 25 microns. Pollen grains can be removed from the air more readily than the particles of dust prevalent in outdoor air or produced by dusty processes, since the latter predominate in the range of 0.1 to 10 microns in size. Most grains are quite hygroscopic and therefore vary in weight with the humidity. Illustrations and data on individual pollen grains are available in the botanical literature.22'23i 24 Geographical distribution of plants known to produce hay fever is also recorded.25'26 The quantity of pollen grains in the air is generally estimated by exposing an adhesive-coated glass plate outdoors for 24 hr, and then counting cali brated areas under the microscope. Methods are available for determin ing the number of grains in a measured volume of air25'27128 but their greater accuracy has not caused them to replace the more simple gravity slide method used for most pollen counts. Counting technics vary some what, but the daily pollen counts reported in local newspapers during the hay fever season usually represent the number of grains found on 1.8 sq cm of a 24-hr gravity slide. Hay fever sufferers may notice the first symptoms when the pollen count is 10 to 25, and in some localities the maximum figures for the seasonal peak may approach 1000 for a 24-hr period, depending upon the sampling