adlted by
MALCOLM M. RENFREW University of ldaho
MOSCOW,ldaho 83843
Flammable Liquids-Why
the Hazard?
Arthur Stevens Consultant, GCAIPrecision Scientific, Chicago, Illinois Twenty-five percent of all school and college fires begin when flammable or combustible liquids ignite accidentally, according to the 14th Edition of the "Fire Protection Handbook." oublished bv the National Fire
these questions we must be familiar with the basic chemistry of fire along with the characteristics of flammable liquids themselves.
~ h b m i s t of r ~Fire While combustion is more complex than illustrated by the traditional fire triangle, (see fieure). it will suffice as a euide to our undtmrnnding. Three essentml i n g r r d i r ~ n ~ musr comt,inr in wrrrrt proportims to p w mil a tire orru-fuel, u x y p n , and heat. Htmwe any one of rhrsc elements and chwe can ht nt, fire. Srpararion ~rftherlemrntsuf the triangle is the ohirctiw in dcvelu~mp. methods and equipment to provide fo; th; safe handling of combustible materials.
Oxygen
Flammable Liquid Characteristics A r t h u r M. Stevens received his B.A. from Denison University. In 197f he established Stevens Associates a: a business communications and marketing firm t o serve the needs 01 manufacturers of industrial fire pmteetion and safety equipment. He is the author of articles on handling flammable liquids for Notional Safet3 News, Professional Safety, Indusfrioi Research, Research and Deoeloprnent, and several other trade publications.
Flammable liquids themselves are not the problem. It is the vapors they emit that cause difficultv. Mixed with air. vaoors of flamspeed of heat generation, with its aecompanying accelerated formation of vapor, causes uncontained flammable liquid fires to be fast-spreading and violently destructive. Terms describing vapor concentrations and emissions indicate the relative hazard of different liquids. (Continued on page A123)
Volume 56,Number 3, March 1979 1 A l l 9
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hazardous concentrations of vapor will he minimal; or (c) he installed in a location subject to positive ventilation inherent in the refrigeration which prevents aecumulations of hazardous concentrations of vapors."
Noihpwn: ts the l.west trmprmrurc at which a liqutd g l v w off sufiirwnt v.,pors to f#xman ignitahle mixture with the air near the surface of the liquid. By definition, all liquids with a flashpoint below 10O0F. are Unfortunately, many laboratories using designated as "flammable," In the laboratory refrizerators fail to reeoenize the laneuaee " - " of they are normally handled a t temperatures this standard. Confusion reiens! " hieher than the flashnoint. Huucehold refrigrruturs, altlwu~h1trtr:d hy l ' r p l m , t c ,,r t'lnrnmahlr Knntc l a the 1'nrlrrur:trrs I.ahurator~e\, u r r e n c w r d r prrrentadp rangr 01' IlquiJ vapor in mr. !,I manufactured, tested, or approved for \ h m r , uithin uhwh ~ ~ n ~ t : o n r o n < k c u r . T h signed, r commercial use. extremities are known as the lower and upper "Commercial refrigerators" are UL listed flammable or explosive limits. If the percent for food storage, not the storage ofhazardous volume of vapor is less than the lower limit, chemicals. the mixture kill not ignite because it is too The "safety or erplosion-safe" refrigerators lean. Conversely, if the percent volume of used in times vast have not been tested and vapor exceeds the upper limit, the mixture is approved by any nationally recognized aptoo rich to burn. The flammable range varies proval agency. widely among common liquids. For exThere no longer is any reason for uncerample: tainty about refrigerators acceptable for use in laboratories. Underwriters Laboratories responded to the specifications outlined in % in mixture with air NFPA 45 and developed extensive testing Gasoline 1.4- 7.6 procedures to assure that listed refrigerators Acetone 2.6-12.8 could he made available. oravidine a means Ethyl Alcohol 3.3-19 fiw eomnlianee with OSHA reeulat;ons. (The Carbon Disulfide 3.3-50
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Vapor Density is an extremely important
characteristic to be recognized when establishing protective measures far storing and handling flammahle liquids. As used by workers in fire protection, vapor density is the weieht of a volume of oure eas cornoared
in pmkets and accumulate, forming explosive mixtures near the floor. Since practically all flammahle liquids have a vapor density greater than 1,ventilation systems must have their intakes a t floor level for maximum ef-
appliances must he located above the region of dangerous vapor eoncentralion and en,.l,>.NI
Fire Protection for Laboratories Using Chemicals," as: "Refrigerators or cooling equipment used to store or coal flammable liquids shall he designed or modified so that the storage compartment, including the door and door frame, meets the requirements for Class I, Division I locations, as described in Article 501 of the National Electrical Code, NFPA 70.1915. All electrical equipment mounted outside of the storage compartment shall either: (a) be suitable for Class I, Division 2 lacations if located in areas such as the machine compartment at the bottom of the refrigerator where hazardous vapors may be present due toleaknge or opening of the storage compartment door; or (h) he installed above the storaee eom-
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listed or approved by a nationally recognized testing laboratory is acceptable). GCAIPrecision Scientific, leading manu-
&und several ootential sources of ienitian.
terminals, and condenser fan. If vapor-air mixtures within the explosive range are present in the starage compartments of these refrigerators any one of the ignition sources listed can set off an explosion. Two years of development work and testing followed. As a result the Precision Model 813. Flammable Material Refrigerator, now is providing safer working conditions for laboratory workers, technicians, and students. In compliance with the specifications, the thermostat is outside on top in anenclosure; the hot wire compressor relay is also outside in an enclosed box. The compressor is explosion-proof and is hermetically sealed. There is no light; no switch on the door. Installation of the refrigerator is simple. The unit is ready to plug in. This refrigerator permits safe storage of flammable liquids such as ethyl ether, hexane, acetone, methyl ethyl ketone, alcohols, solvents, and biologicals in a non-hazardous atmosphere. For storage of flammahle materials in a hazardous atmosphere engineers a t "Precision" have developed the Model 814, a conventional "explosion-proof' unit. It is designed for installation in Class I, C&D areas. While correct installation of this refrigerator is relatively expensive, such installation is vital to protect against ignition of the dangerous vapors in the area. Listing by Underwriters Laboratories assures the user of compliance with OSHA regulations (1910.309). Containment is the key to the storage of flammable liquids. Both liquid and vapors (Continued on page A124) Circle No. 114 an R e a d e r i Inquiry Card
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must be "contained" to control the fuel leg of the fire triangle. Liquids should be stored in approved "safety cans," with spring loaded pressure-relief caps, and flash-arresters in the spouts. Safety cans are available in sizes from 1pt to 5 gal. While NFPA and OSHA regulations permit storage in glass t o overcome excessive corrosion, or when impurities would be imparted by traditional terne plate containers, we caution that glassshould be used nnlv .a n last resort. Tests should be concans. The quantity of hazardous chemicals present in laboratories desirably should be kept at an absolute minimum. Fire protection regulations state that when quantities stored in any one fire area exceed 10 gal. specially designed cabinets must be used for the storage of individual containers. If metal, these cabinets must beof dnuble-wall construction with 1% in. ofair space as an insulating barrier between the walls. NFPA No. 30 and OSHA regulations go on to say: "Storage cabinets shall be designed and constructed tolimit the internal temperature to not more than 325'F. when subjected to a 10-min fire test using the standard timeltemperature curve as set forth in standard methods of fire tests of building construction and materials, NFPA 251-1969. All joints and seams shall remain tight, and the door shall re-
A124 1 Journal of Chemical Education
main securely closed during the fire test. Cabinets shall be labeled in conspicuous lettering, "Flammable-Keep Fire Away?' Disposal of wastes is becoming a major concern in laboratories across the country. Because flammable liquids will separate from water, hazardous vapor concentrativns will develop in sewer systems if they are simply flushed down a drain. Good practice dictates the use of safety disposal cans a t each work station enabling students to empty beakers or flasks conveniently. These containers must then be removed from the laboratory and emptied into protected drums at the end of eaeh day. Disposal of the drums becomes more complicated and generally is controlled by local EPA regulations. Frequently burying sites are designated and packing procedures are specified. A large high school district in the suburban Chicago area learned that to receive a disposal permit the following packing was required. 1) All materials must be placed in an oildry compound or equivalent and packed in watertight 55-gal. steel drums. 2) Each drum must contain compatible material, i.e., acids in separate drums, oxidants isolated in separate drums, reductants isolated in separate drums, etc. 3) Each drum must be identified as to chemical contents and volumes with eaeh list keved to an aoomoriatelv
letter stating the chemical descriptions and drum packaging breakdown; more imperative that the generator states each drum has a plastic liner with a watertight locking head. Upon satisfactory completion of these procedures the drums will be accepted far disposal by a land-fill site approved by the EPA. Check local regulations for acceptable disposal methods in your area.
Definitions Class I , Division Ilocotions-locations in which (1) hazardous concentrations of flam-
such gases or vapors may exist frequently hecause of repair or maintenance operations nr hecause of leakage, or; (3) breakdown or faulty operation of equipment or processes which might release hazardous concentrations of gases or vapors and might alsocause simultaneous failure of electrical equipment. Class I, Diuision 2 laeotions-location in which (1) volatile flammable liquids or flammable gases are handled, pmcessed, or used, but are normally confined within closed containers or systems from which they can escape only in case of accidental rupture or breakdown or abnormal operation of equipment; (2) in whieh hazardous concentrations of eases or vaoors are Drevented normallv bv ~, ~. p { w w e il~whantcalvrnrhuc.n, o r t.3 which 3re nlljaccnl I,, llut nu1 suitilnly C U I $111lmm c1a.> I , I),W
