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194 CHAPTER 10 _________ 1946 Guide Table 6. Approximate Limits of Flammability of Single Gases and Vapors In Air at 'Ordinary Temperatures and Pressures a Gas or Vapor Lower Limit Per cent by Volume l Upper Limit Per cent by Volume Closed Cup . Flash Point F Deg. Acetaldehyde-- _ Acetone_________ --__ ___ _ Acetylene1* Aliyl alcohol Ammonia ' 4.0 2.1 2.5 2.4- 16.0 .57 13.0 80 . 27.0. ' -17 0 70 Amvl alcohol Amyl chloride Amvlene . Benzene (benzol)___________ Benzyl chloride____________ 1.2 1.4 1.6 1.4 1.1 8.0 91 12 140 Butane . Butyl acetate______________ Butvl alcohol Butylene............................... .... Carbon disulfide - 1.6 , 1.7 1.7 1-7 , 1.0 8.5 15.0 9.0 50 ' -76 72 84 '-22-. Carbon monoxide Crotonaldehyde ... Cyclohexane Cyclopropane__________ ____ Decane.... ...................._......... 12.5 2.1 1.3 ' 2.4 0.67 . 74 15.5 8.4' 10.3 . 2.6 55 1 115 ` Dichloroethylene (1, 2)____ Diethyl selenide____________ nirtvan F.thane Ether (diethyl)........................ 9.7 . 2.5 : 2.0 , .......... 3.1 1.7 . - 12.8 22.2 < 15.0. 48.0 .... , 43 65 . -20 Ethyl acetate... Ethyl alcohol.______________ Ethyl bromide ................... .. Ethyl cellosolve____________ Ethyl chloride 2.2 3.3 6.7. 2.6 3.6 ! 11.5 19.0 . 11.3 . 15.7. ' , 14.8" ' 24 - .; . 55.. 104 " '--58 ' Ethylene....Ethylene dichloride._______ Ethyl formate-_____________ Ethyl nitrite. Ethylene oxide. __ _ . ... . 3.0. ' . 6.2 . 2.7 "3.0' " 3.0 : 34.0 15.9, 16.5 ` -* 80 ,, 55 . -4 -31 . Furfural (125 C) Gasoline Heptane._____________ '._____ Hexane. .............. .......... Hydrogen cyanide_________ 2.1 `1.3 - 1.0 1.2 5.6: . , ,6.5 6.0 6.9 40.0 '. " 140, . , -50 ` 25 -7 ' -0 . Hydrogen__________ !________ Hydrogen sulfide....:_______ Illuminating gas. _____ ... Iso-butyl alcohol-- Iso-pentane.............................. 4.r- ' ` 4.3 -- .. 5.3 - 1.7 1.3 Iso-propyl acetate______ ...... Iso-propyl alcohol_________ : Methane** .......... - 1.8' : . 2.5 . 5.0 - ' 74' 45.5 31.0 ------- ; 7:8 .' 15.0 . 82 43 ; 53 . "Adapted from: Limits of Inflammability of Gases and Vapors, by H. F. Coward and G. W. Jones (U._S. Bureau of Mines. Bulletin No. 279. 1939); Properties-of Flammable Liquids, Gases anH Solids (As* sodated Factory Mutual Fire Ins. Cos.; January. 1940); and National Fire Codes for Flammable Liquids, Gases, Chemicals and Explosives--1945' {Nationdl'Pire Protection Association). ' " bTorbulent mixture. - ,. - *Closed cup refers to the equipment used in flagK point determinations'. ` Air Contaminants 195 > Table 6. Approximate Limits of Flammability of Single Gases and Vapors In Air at Ordinary Temperatures and Pressures (Continued) Gas or Vapor Lower Limit Per cent by Volume Methyl acetate. -- ----- . Methyl alcohol. -- . ... Methyl butyl ketone. '.------Methyl chloride___ -........... 3.1 6.0 13.5 . 1.2 8.0 Methyl cyclohexane. Methyl ethyl ether.------------Methyl ethyl ketone............. Methyl formate--- -------------- Methyl propyl ketone.-------- 1.1 2.0 1.8 5.0 . 1.5 Natural gas.........................-- Naptha (benzine)______ -- Naphthalene_______________ Nonane_____________________ Octane.....................-........... -- 4.8 1.1 0.9 0.74 0.84' Paraldehyde..... .............-- Propyl acetate...... .--............ Propyl alcohol.........- 1.3 1.4 2.4 1.8 2.5 Propylene dichloride___ -- Pyridine (70 C)________ ___ Toluene (toluol)........... ......... - 2.0 .3.4 2.1 T.8 1.3 Vinyl ether___ ________ ____ Vinyl chloride-___ ___________ Water gas (variable)_______ Xylene (xylol)........... ............. 0.8 1.7 : 4.0 6.0 . 1.0 -- Upper LiMrt , Closed Cup Per cent by Flash Point Volume -F Dbg. 15.5 36.5 14.5 8.0 19.7 15 54 - ..... 10.1 11.5 22.7 8.2 25 --35 30 : -2 . -- 13.5 6.0 2.9 3.2 20-45 174 88 56 ____ ' 8.6 \ 9.5 8.0 1 58 59 11.1 14.5 21.5 12.4 7,0 59 . 68 40 27.0 22.0 70 6.0 - 95 ... 63 ` meter 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: Investigations on the flammable.characteristics.of dusts are currently made at 0.1 and 0.5 oz per cubic foot15-*1. ATMOSPHERIC POLLEN The properties of pollen grains discharged by weeds, grasses and trees and responsible for hay fever are-of, special interest to engineers who design equipment for their removal from indoor air (see Allergic Dis orders in Chapter 13, and Air Cleaning Devices, .Chapter 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 pf 15 to 25 microns. Pollen grains can be removed from the air more readily than the parti cles of dust prevalent in outdoor air and found near dusty industrial 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