in the Chemical laboratory Edited by N O R M A N V. STEERE, 140 Melbourne Ave., S.E. Minneapolis, Minn. 5541 4
LI. Safe Use of Flammable Liquids in Laboratories A. J. SHAW, Technical Services Deportment, The Protectoseol Company Flammable liqttids can be fouud in virtually every laboratory. A basic knowledge of the properties of flammable liquids and sn understallding of the precautiom required for their safe handling should be prerequisites for all 1nhoratul.y pel.swnel.
Properties of Flammable Liquids Ironically the words "flammable" and "intlammahle" hoth mean the vapors of a liquid can he igltited m d e r normal conditions. However; hecsuse "iuflammahle" implies "no~~flammahle"t,o many, its use has heeu discouraged by the safety profession and furtwmteiy ir heading toward exthmtiou. As nvted above, the vilpors of a f l a w mable liquid rather than the liquid itself, coutrihuk tu fire r explusion. Sioce these vspurs can travel to sources of ignition, flammable liquids mnst always be kept iu sealed cuntainem w h e ~,lot ~ in actual use. The fire triangle is often used to illustrate the causes of fire and explosioli. The three "sides" of the triangle are fuel, heat, and oxidizer. In considering flammable liquids {.hefuel must be in t,he form of a vapor or mist. To dramatize this point, many lectnres on safety use kerosene to extinguish matches. Oxygen of course is always present in habitable areas, again poi~kingout the need far keeping flammables in closed containers. However, the mere presence of these two "sides" is insufficient; the fuel vapor and oxidizer must be ill proper proportion if fire or explosion is to occur. These proportions are called flammable limits and are generally expressed iu terms of the percentage by volume of vapor in a vapor-air mixtwe. The limits for pet,roleum producbs are rtpproximately from 1 to
Table 1. Pro~eritiesof Common ~lommobleLiquids
8y0 vapor while the flammable limits of ethylether are 1.9 to48%vapor. The "heat" must he a t least equal to ignition temperature; however, only a small portion of the vapor-air mixture need he raised to ignition temperature to cause self-sustaining combustion. While Bunsen burners and other open flames are obvious sources of ignition, friction, and static sparks lasting only a fraction of a second can cause fire or explosion. A cigarette lighter illnstrates this point write . simply. The characteristic of a flammable liquid most often used to indicate its relative hazard is its flash point. This is the lowest temperature of the liquid a t which it will give off sufficient vapors to form a flammable vapor-air mixt,ure. Flammable liquids with flash points considerably above room temperatures obviously pose less hamrd thalx ethyl alcohol or carbon disrdfide with flash puilrts of 55 and -22"F, respectively. IIowever, many lab operations i~ivolveheating flammable liquids which can easily raise t,he temperature of any flammable t,n its flash poil~t.. IIeiltiog also inere~lies vapor pr%%swe resdtiug in nn iucre~sedrate of evaporation and the danger of boil-over. Finally, heating can csose a,~toignitiur of the vapor-air mixture. (The ignitim temper.atnre of carbon disdfide is 212°F.) The lumber of i a b o ~ a t w y fires and explosions ittt~.ibutedtu either igtm.ance or carelesstress of the basic characteristic3 of flammable liquids is tragic. There are several chemi~tryhxndbm,ks which list the prapert,iea of most flammable liquids. Additional sources ale the National Fire Protect,ion Associntiml, and Underwriters' Laboratories. There are sevwal other characteristics of flammable liquids that Iahhoratmy personnel should familiarize themselves with, not only for their uwnsafety hut for the safety of their fellow workem. A large nwnher of Hammahle liqrdds have specific gravities of less t h m 1, and in addition are liot miscible ill water. For these reasow flammable liquids-even waste--must itever be prrured d u w ~ sii~ks, flvor drains, elc. This is usually prohibited by mrnlieipnl, indust,rial, and ilniversit,y codes and regulations. Safetytype liquid waste cans ahould be used fur disposal and accumulations removed dsily. While many flammable liqnids have specific gravities of less than 1, %hevapor densities of all flammable vapors are greater than 1. h result, these vapors settle to the floor, flow down stairwells and elevator shaftx, and present dangers often far removed from their source. Proper
...a
am
feature
ventilatiou facilities must be pmvided and used. Finally, the vapors of flammable liquids can present hasardv of toxicity = well a3 fire and explosion. Limits for dsily exposure which have been recommended by the Amerioan Conference of Governmental Ind~tstrialHygienists range from 0.001 to 0.01%, well below respective flammable limits.
Responsibilily for Safe Flammable Handling The first step in any safety program is to designate someone to init,isfre and implement it. Committees and assistants can hoth be valuable, hut unless one person is placed in charge and made responsible the program is liable to be ineffective if not nonexistent. In an academic laboratory with its constant student tunmvey, the selection of the responsible person ohviuuvly limited tu faculty and staff. In an industrial or governmentnl facility the responsible person need not necessarily be the head of the laboratory, pmvided he is given the support necessary Lo carry out the program. Once desigtrated, the pernm responsible for safety will have tho d~lhiousduty of "poking his nose into everyone's huriiness." First of all, he must learn what, flammables a x heiug wed and stored within the laboratory and familial.iae himself with their eharaeterislics. He will have to determine if both variet,y and vulome stwed within the lahorittol.y are cormistent with actual needs. A d r i m storage room with its special safety pmvisions is a far better locstiun than the laboratory for the little-used flammable liquids thnl "mighl hc needed some day." "Forgnt,ten" quantities of isopropyl ether have also hew fu~iudt~ hecwne uiwtahle, capable of explodiug witb devaitating force ~mlessilibibilors have heen added. Limitiug the q ~ ~ a u t i of l y flammahlea is a bwic rule of lahumtory safety not only hecausc they are potential svirrces of fire
After determinirlg what flamhnhles are used, the laboratory safety director must learn how they are used. Parbicular attention should he given to any operation involving the heating of flammables either by open flame or electric hot-plate. Is the persou familiar with the ropert ties of the flammable(s) he is osh~g? What potential dangers are present or could arise? To p u t i t morepositively, is it possible that a flammable vapor-air mixture will be formed and exposed to a. source of heat equal to or above ignition temperitt~u'e? Remember-if the three sides of the fire triangle are present as defined earlier,
(Continued m page A 8 B )
Volume 45, Number 7 0, October 1968
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fire or explosion will always occur! The obvious next step then is to take the necessary precautions to eliminate or, a t the very le&, greatly minimize the potential for fire or explosion. Sources of ignition must be removed, flammable vapors drawn off by suitable ventilation, static buildup prevented by proper grounding, safety containers used to control evapors, tion and guard against accidental breakage and readily-available fire extinguishers suitable for flammable liquid fires. Another aspect of the safety director's duties is the investigation of mishaps. Any unplanned event or oncontrolled escape of flammable liquids or their vapors should be considered s m k h a p . Investigation should cover: 1. How to prevent, reoccurrences and 2. What could have happened under the most mfavorable conditions. Unless flagrant carelessness is involved, reprimands and emhsrrassments should be held to the minimum to encourage the fullest disclos~re and cooperation on the part of personnel involved. Finally, and perhaps most importantly, the laboratory safety director mnst agsume the responsibility for training laboratory personnel in the basic fundamentals of flammable l i q ~ ~ i das ~ proper d procedures snd use of yafety equipment in handling them. Many of the leading industrial, academic, aud governmental laboratories
have published safety standards for the safe hhandling of flammables within their laboratories and require personnel to familiarize themselves with thesestandards before beginning work with flammables. As Bill Torney, Corporate Safety Director, Texas Instruments, I)allas, stated in a 1966 a d d r e s to the N a t i u ~ ~ Safety al Congress concerning safe use of chemical8, "There is no competition between eompnnies in safety ideas." In the absence of established standards, the newly designated laboratory safety director will find most firms and mliversities more than willing to lend their standards. Two valuable booklets in establishing a flammable liquid handling program far laboratories are "Flash Paint Index of Trade Name Liquids," puhlkhed by the National Fire Protection Association, and "Bulletin 222 (Rev.), Chemistry far the Safety Man," available through the Superintendent of I)ocuments, US.Government Printing Office, Washington, D. C. 111 addition marry specific recommendations can be made by local fire marshalls' offices, leading chemical manufacturers and manufacturers of safety equipment for flammable liquids. Probably the most difficult task in training fellow workers in the safe handling of flammables is motivating them to adopt safe work habits. Certainly ordering someone to "do i t this way or else," leaves something to be desired. On the other hand no one will deliberately cause a fire or explosion through intethonal misuse of (Conlinwd on page AM51
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flammables. The success theu of the laboratory safely director will depend on his sincerity. natienee, knowledge of flammables, -and the support he receiver from his wperiars.
Proper Safety Equipmenl
A very important part of any laboratory safety program is the proper seleet,ion and use of safety equipmeut. The basic safely device for flammable liquids is the safety can bearing the appt.ova.1 of Underwriters' Laboratories, Factory hlotaal, or both (Fig. 1). Unfortonately, lo many peoples "safety" call is any metal can painted red. The primary reason fur using 8. safety can is to prevent t,he three "sides" of the "fire triangle" from ooming C,gether. This is accomplished by a tightly-sealing cap to prevent the escape of flammable vappars, and a flame arrester to prevent ignition of the contents from exterior sources whenever the cap is upen due to filling or empbying. The flame arrester can be traced back to the miner's safety lamp when i t was discovered that flame would not propagate through a, series of small tubes placed fiide by side. Today a typical flame arrester for a safety can consists of a double-walled perforated metal fire baffle, which dissipate8 exterior sources of heat to prevent ignition temperatwe from being reached.
Figure 1.
Safely cans i n u r e in o loborotory
Since flammable liq~lidswill eapcrielice s. buildnp of vapm presswe dne to lemperature increases, x\~lomaticpressnre relief must be provided. This becomes even more critical in the event the coutainer is exposed to fire and is O I E reason why screw cap container-glaw or metal-are nnsuitable for flammable liqnids. In an approved safety can this pressure relief is provided by a spring-loaded cap assembly (Fig. 2). A safety can also includes a seli-closing cap so that. in the eveut, it is dropped or tipped, spillage of flammable liquid is minimized. (A dropped and brnken glass botlle of flammable liquid lacks anly a spark to become n "blulutov Cocktail.") Other safety features uf a safely can inchtde wgged comtruction aud a bottom shock rim; x handle guard to prevei~taccidellbal discharge, RMI welded rather than soldered seams lo prevent failure from ex-
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Figure 2. O w l stoinlers steel safety (Courtesy &The Protedoreal Company.)
Another important piece of mfety equipment for the laboratory in a UL listed, explosion-proof refrigerat,or. The use of an ordinary household type refrigerator for flammables ha? caused several serious laboratory explosions. An approved refrigerator for flammables eliminates any possibility of explosion of eontents from soarks within the chamber as well as eliminatmg the danger of vapors
con.
posure to fire. (Plastic eoutaiirers of flammables are hitaardous in the event of even a minor fire.) Approved safety cuntainers are mailable ill rioes l-pt through 5-gal, roond or oval shape, terne plate or stsiuless steel and are basic to m y fiammahle liquids safety program.
A826 / Journal o f Chemical Educafion
Figure 3.
Padded bottle sarrior.
fl >-.
(Courtesy of The Protectmeal Company.)
surrounding the ~drigeratorbeing ignited by the electric motor. Suitable waste receptacles should he provided for flammable-soaked syabs and rags. Such receptacles provide self-closing covers and a raised bottom to vent off heat, that could lead to spontaneous combustion. Special padded metal guards for highly corrosive flammables that must he k e ~ in t glass bottles miuimize the danger of
breakage and help contain spillage should breakage occur (Fig. 3.) Suitable storage should be provided for flammables when not in actual use. A metal, douhke-wall flammables st,orage cabinet built in accordance with NFPA specifierttian~is mailable and widely nsed for this purpose. The flammable liquids themselves should be kept in safety ron(Conhued a page A8Z8)
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1 r u 1 ~ 4 c r r ctJ, .,afety C > A . I . ~ ., It C3 vIh~cI m-
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Figure 4. Stainless steel nornrnslble liquid disposal con. (Courfery of the Protectoreol Cornpony.1
tainers. Finally, proper facilities must be available for disposal of flmnmable liquid waste if prohibition agaiuinst pouring them down sinks and drains is to be enforced. A special type of safety can is available for this purpose and features a wide mouth opening, protected with a double-walled flame arrester (Fig. 4.) Care must be exercised to ensure against mixing reactive chemicals, and aecomulations should be removed daily.
Labeling Flammable Liquids Once flammable liouids have been
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Journal of Chemical Education
Periodic Inspection and Review
1't111w.~h~,ul~l I ~ iP d ~ ~ ) t i ti!. i ~ dIIW ~ ~ R I . I ~ I . I r c . 11ediv31~ 11. C C , ! , ~ ~ I I :tt.cl I. t h l ~ w a r d , , ~ ~ ~Once a laboratory safety program for handling flammable liquids has been properties of its contouts. Some lahoestablished, a definite schedule for inspeeratories merely indicate the geuerio name lions should be made. Equipment for of the contents and add a, color code to storing and dispensing flammable liquids indicate its classificsliou based on flash should be examined and repair or replacepoint. This is hal.dly sufficient since adment made as warranted. Fire extinditional hazards of given flammable guishers should be checked to be certain liquid might be that it is poisonous or they will be effective if called upon. irritating to the skin, unstable, or reacts Again, the volume of flammable liquids with water. Secondly, laheling only with present in the laboratory should be rename and code does not indicate the basic considered in light of practical need. precautions to observe in usiug the flamPeriodic housekeeping inspections mable liquid nor any immediate first aid should also be schedoled. Fire fighters steps that shodd be taken in the event of oite an old axiom to the effect that a clean an accident. plant or home seldom burns. This can be The Manufacturing Chemirts Associa,equally applied to the laboratory. Safe tion is au authoritative source of informahousekeeping goes somewhat further than tion 0 1 1 the properties and hazards of merely keeping everything tidy; it means flammable liquids as its membership condetermining whether various flammables sists of almost the entire chemical manuand combustibles stored within t,he laborafacturing industry. Therefore, the labotory are really necessary and if not, p r a F p t ratory safety director would be wise to rely removal of them. Safe housekeep~ng upon the MCA2s recommendations for a. means that everyme responsible for a. labeling system rather than devise one on given work ststion or area knows what he his OWL* The NFPA also has a recomhas an hand and what hazards they present mended system of labeling flxmmahle toward causing a fire, oontributing to a liquids although it perhaps is not as apfire, and endangering fire fighters. plicable to chemical llaborstories. PresAn "outsiderN-whether from another sure-sensitive labels are available from department or from outside the company several manufaet,~trers. or sohool-can be of great assistance in * Editor's Note: I t would be a significonducting these periodic invpectiow cant contribution to laboratory safety if simply because he will be more likely to the MCA would establish and maintain a view conditions with "fresh" eye and registry of all accepted precautionary (Continued o n page A850) labels.
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observe operations with greater objeotivity. This person, of course, must be familiar with flammable liquid properties and laboratory procedures.
Conclusion While safety standards and regulations may vary in different types and sizes of laboratories, certain ones are more or less basic and are listed as follows: 1. Lahoratoriesshould be well-lighted. 2. There should be a t least two exits located a t opposite ends of the room. 3. Locate most hazardous activities away from exits.
cal purity of liquids, use containers of stainless steel or other special metds. Jacketed glass containers should be used only when n o acceptable metal container is avd8,ble. 8. Label containers plainly. 9. Keep flammable liquids away from beat and direct sunlight. 10. Do not heat flasks containing flam.. mable liquids directly over burners. Use water bath, sand or other suitable materials for indirect heating. 11. Have exhaust ventilation a t upper and lower levels of rooms to remove hoth light and heavy vapors. Always use a hood or special ventilation where high concentrations of vapors are given off. 12. Use explosion-proof electrical equipment.
13. Do not pour flammable or corrosive wastes down the drain. Use sealed dispo4. Mount fire extinguishers in full sal containers designed for that specific view, within easy reach and away from purpose. Wastes can then be safely earhazardous spots-preferably near exits. ried away for proper disposal under com5. Have self-contained breathing petent supervision. masks handy and located near fire ex14. AU rags, hoth clean and dirty, tinguishers. They are often needed in should be stored in metal containers with fighting fires. selfclosing covers. 6. Have a. fire blanket ready for i ~ ~ s t a n t 15. Have a n approved water bath use to extinguish clothing fires, and provide instantly available a t all times for flushing special elothiug where needed. eyes or body in case of acid burns. 7. Keep only a minimum quantity of flammable liquids in the laborstory, and Editor's Note store them in approved fire and explosionThe editor would welcome suggestions proof containers. For maintaining chemifor future articles in the Safety series.
