mfety in the chernkol loborotory
edited by MALCOLMM. RENFREIV University of Idaho Moscow, Idaho 83643
Safe Chemical Storage: A Pound of Prevention is Worth a Ton of Trouble D a v i d A. Pipitone and Donald D. Hedberg Lab Safety Supply Co., P.O. Box 1368, Janesville, WI 53547
Nothing is more thrilling to chemist, teacher and student alike, than a graphic demonstration which illustrates the fundamental reactivity of chemicals. Sodium fizzling in water, the exothermic neutralization of acid by base, and the feather a t the end of a ten-foot pole detonating the ammonia-iodine formed nitrogen triiodide, among others, have fascinated many audiences. Yet not so noticeable or controllable is the potential reactivity among stored chemicals which can cause a "ton of trouble" in the storeroom and surrounding area. Storage problems are as numerous as there are storerooms.' This paper will attempt to identify some positive solutions for the overall range of storage difficulties. A checklist will pay attention to the specific storage matters that cannot fall into any general category except warnings. The general categories that govern safety in the storeroom include facilities, housekeeping, precautionary measures, inventory, and vigilance through upkeep and good practice. Proper design and construction, ventilation controls, cleanliness, and anticipation of potential reactive hazards undergird the effort to make the storeroom safe. We have conducted several surveys of the current storage situations among professional chemists and educators. The one-page survey consisted of various statements about their practice of chemical storage which participants marked "Yes" or "No." Participants were given achart illustrating safe procedures for storing chemicals in return for completing the questionnaire. Surveys were conducted a t two recent national conventions: The Pittsburgh Conference (March 1981 in Atlantic City, NJ) and the National Science Teachers Association National Convention (April 1981 in New York, NY). The results are summarized in Tables 1and 2. The results from both surveys indicate weak spots in facilities (insufficient exits and humid atmospheres), poor information vital t o storage (such as room identification and inventory labeling), and failure to take precautions against reactive hazards which can
lead t o fire and disaster. A "ton of trouble" is lurking in some of these storerooms. Even in the best organized storeroom, Table 1. Results of Survey Conducted at the 1981 Pittsburgh Conference Statement
Are chemicais stored in a specially designated room? The chemical storeroom is identified as such with a sign. The chemical storeroom has two or more clearly marked exits. All chemical containers are clearly labeled as 10 their contents. All chemical containers are clearly labeled With both receiving and disposal dates. Chemicals are stored alphabetically. Chemicals are stored by class, i.e.. oxidizers with oxidizers, flammables with flammables, etc. Incompatible chemicals are physically segregated. Peroxide-forming chemicals are labeled with receiving, opening, and disposal dates.
Yes
NO
67%
32%
NO Answer
Basic t o chemical storage are the storage facilities themselves. Sources in the literature indicate necessary safety features. The room must be identified with a sign as a chemical Table 2. Results of Survey Conducted at the I981 NSTA National Convention Statement DOyou havea chemical storeroom? Does your storeroom have two or more clearly marked exits? Is me air in your storeroom dehumidified? Are bottles of chemicals labeled with receiving and expiration dates? Are chemicals arranged alphabetically on sheives? Are chemicals arranged by class-i.e.. oxidizers with oxidizers, flammables with flammables. etc.? Do you usesafely cans while storing flammables on the lab bench or counter top? Are batlies of concentrated acids stared separately from inorganic bases?
42
33
90
32
63
45
65
39
One hundred sim-We prof~lonsl dxmisls participated in me survey.
there is need for continuing improvement and upkeep. Appropriate knowledge and practice, when applied wisely, will reduce storagerelated hazards.
Yes
No
No Answer
90
9
1%
43
52
5
13
62
5
28
69
3
73
25
2
48
51
1
24
70
6
76
24
...
.
one hundred fw-three professional science educators participatedin the survey.
'
Davison, H. F., "Salety First in Storing Chemicals." J of CHEM.EDUC..2, 782 (1925).
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(Continued on page A160) Number 5
May 1982
A159
formation available in ease of exposure. Using just a piece of tape which has the word Acid on it, without identifying the type, concentration, and other pertinent data, is to be avoided-not only for safety reasons but also for protection from liability should an accident occur while handling. Figure 2 shows a storeroom, with a Caution or Danger heading t o alert maintenance and other personnel that this is no ordinary room. The room should be locked and accessible to authorized personnelonly. Layouts of the room aredictated by the type and amount of chemicals to he stored. Vaults designated t o store flammables should be designed in accordance with NFPA 30 "Flammable and Combustible Liquids Code" (1976-Section 4 . 6 ~ 30. 48). Each storeroom should have clearly marked, easily reached exits. The shelving units in the room should be fastened to the wall or floor. The shelves should be constructed of unpainted wood or of metal coated with a corrosion-resistant uaint. Weieht limits of the shelves should be " determined and posted. Carr muxr he tnktn not to exceed thk weight limit. Overcmad~ng a shelf with bottles is to br avoided. Sewml sources recommend the use of raised edges fastened to the shelf to prevent containen from "creeping" over the edge (Fig. 1). As an added safety factor, bottles should be smred below eye level of the smallest person to use the storeroom.
WARNING FLAMMABLE, MAY CAUSE FIRE I ~ Pa w imm
IA
neat, rmns. and w n name.
KaaD contansr o,osad "la n n adaqlala *snl,i.l~n. A W * ~w o n g a d breatnmng r a w p m l o n ~ rsllsalad d m M".
*
Figure 2. Label to identify repackaged chemicals (Courlesy T8B Westline). label which has the proper elements far safety identification. Depending on the nature of the repackaged chemical, graphic markings should be applied to the container to alert personnel to handling-related hazards (Fig. HI
Figure 3. Graphic labels show hazards of chemicals.
Figure 1. Applying raised edges m stwage shelves. The nature of the storage environment is important to extend theshelf lifeof chemicals and guard against unwanted reactions. Chemicals should be stored in a cool atmosphere, out of contact with direct sunlight. Placement of containers near localized beat sources such as radiators, heat vents, or hot water pipes should he avoided. Stored chemicals require a dry atmosphere to prevent contamination or degradation from condensation. Good ventilation coupled with a dehumidifying system are essential. Most chemicals are safely stored in their original container. The cap or closure should allow an airtight seal and he replaced if necessary. (An exception is nitric acid, which may have a self-venting cap). Chemical-resistant containers are available should the original container leak or break. Vessels made of borosilicate glass, polyethylene, polypropylene, and Teflon' can be used for a broad range of chemicals. Also popular are plasticcoated horwilicate elass bottles which retain the the liquid in a plcs;~c..en\rl~~~e"should I r ) r t l ~hrenk due to rough handling. Shuuld repackag~ngbe necessary, the new container must contain sufficient information t o identify the contents, provide hazardwarning statements, and have first aid in-
A160
Journal
of Chemical Education
types deemed acceptable for compliance: a metal cabinet with a double-wallconstruction (I1:-in.aw space betueen) made uf lo-gauge stecl, and a wooden cabinet mnde of l-!n.thick hieh-drna~tv nl\woud. The hasic Rmr. .. . tion of these cabinets is to protect flammable liquids long enough in a fire to allow fire fighters to enter and extinguish the flames. 'I'hrre are nu nlrrenr standards fur wnrmg a cabinet. Allowing \spars p ~ s w e l yimdlffiise fmm n cahinet wrrhout further prc,trrtim runs the risk of ignition. Several metal cabinets commercially available are fitted with vents which have integral flame arrestors to control flashback. In the opinion of this author, ventilation of these cabinets should be done only when facilities are available to exhaust vapors outside the building, and then with the use of an explosion-proof blower (Fig. 5). Cabinets are also employed for the storage of acids and other chemicals which demand spwlnl rrpatmenr A#id rahinets. f < ~ r ~ s a m p l t . pnnwir a direct means of ~cgrrgstiny,corn,sive, concentrated acids. Bottles of acids are lesslikely t o be knocked over when stored in
Secondary storage facilities such as cahinets can he used inside a storeroom or laboratory. The most common form of cabinet found in these places is employed for the storage of flammable liquids (Fig. 4). Cahi-
a cabinet. Cabinets made of epoxy-painted woad or metal or of Type 316 stainless steel serve this purpose. There should be a regular place for storing chemicals, and a cabinet nicely meets this need. All especially reactive chemicals can best be protected by storage in a eabinet. In the case of water-reactive chemicals, such physical segregation is helpful in countering a fire. A Class D fire extineuisher can be auulied directlv to the cabinet and its con&nts.
hood" with a vapor adsorher
Figure 4. A metal storage cabinet with self-closing door fw flammable liquids. nets designed for this p q m e are required to he constructed i u as u, meet a ten-minute fire
lest as specified b) NFl1t\ Code 231. OSHA (29CFH 1910.10fil and NFI'r\ Nu. 30 list two
Precautionary Storage Measures Providing a good "home" for chemicals by supplying adequate ventilation, a cool atmosphere, and other optimal conditions is only part of the solution for safe chemical storage. I t is also necessary that the "neighhars" eet alone with one another. Some rhemiralr such wsodium chloride, sand.md illuminum oxide are fundamentally inert and require no addi~ionalprrrautiorl other than good housekeeping. Some incompatible chemicals, however, must be kept apart. Arrangements t o prevent accidental mixing of dangerous chemicals upon leakage or breakage of containers unfortunately is not a common practice. The most common and convenient way to arrange chemicals on shelves is t o do so in alphabetical order. The advantage is that a chemical is easily found, retrieved, and returned to stock. A grave danger lurking in this practice is that incompatible chemials can
'110 V Slnplm Ph.r 116th KP. Y G Q RPM E x p W pmf Motor, 220 CFM Q IN" SP. CmtrHupal Fm with Alum. Whssl
Figure 6. Chemical resistant trays for storing corrosive liouids.
Ramore 2" u p and
connect 2" flexible metallic exhaust tub. ing lo fan.
LO-i ordinanca rnJu Ibtions require 1 h . r flammable liquids be kept in approved safety Mntainarf 81 all tima.
Segregate acids from chemicals which could generate toxic or flammable gases upon contact, such as sodium cyanide, iron sulfide, calcium carbide, etc. Segregate acids from basis. Bases Segregate hases from acids and other reactive compounds. Flammables Store in aoaroved safety cans or cabi.. nets. Segregate from oxidizing acids and oxidizers. -~-.--
Figure 5. Ventilating a storage cabinet for flammable liauids.
end up next to each other, resulting in a ticking time bomb. A disaster could occur if hottle breakage rpaulted in the mix~ngof sodium cyanide with concentrated sulfuric acid, generating toxic hydrogen cyanide gas. Alphabetical storage in this manner cannot guarantee a safe storeroom. Another method for arranging chemicals has been to group them so that the correct type of fire extinguisher can he used should a. fire break out in that part of the storeroom. This type of "disaster prevention planning" has alogical base hut could breed unnoticed incompatibilities which actually could generate a fire. Random placement of chemicals is the worst of all types of arrangements on storeroom . ~ - shelves. ~ - ~ A prudent measure for stonng chemicals inside the storeroum and out 1s tc~h~oupthem according to reactivity classes. Incwmpatible groups can be physically segregated to avert even accidental contact, while incompatible chemicals which share the same class can he separated. This storage measure guards against unwanted dangerous reactions and is based on common sense. Take acids as an example of a reactive class of chemicals. A number share the same chemistry of the hydrogen ion: acetic acid, hydrochloric acid, hydrofluoric aeid, nitric acid, perchloric aeid, sulfuric acid, et al. Although all may act a t different rates with another compound, sodium hydroxide for example, the chemical reaction of neutralization will occur for each acid. At bieh ~.concentrarions a highly exothermir reaction will orcur which may be uncontrullahle. Sodium hgdnxide, potasslum hydruxide, and other metallic hydroxides, metal rarlwnates, and h~carbonateswill undergo a neutralilatiun rearr~onw ~ t hacids, which is fine for demonstrations and titrations. Storage of concen~~~
~~~
~~
trated solutimw of acidr in the proximity of bases, however, prermm potential dangers resulting from acrid~ntalmixing. These two classes, then, are incompatible, and members should be physically segregated. Furthermore, it is important to determine the incompatibilities which are inherent within a specific reactive class of chemicals. For examole..,. elacisl acetic acid is a combustihlp liquid lhmitnhlt hy ;inoxidizing atld u r h a*uunccntraled nitric, peruhloric, or iulfuric acid. Thus acetic acid must he segregated from the oxidizers. The several classes of chemicals which deserve special attention include acids, hases, flammables, oxidizers, water reactive chemicals..., ovronhoric substances.. lieht-sensitive .. chpmicali, prmxiclizahle compmmds, and tuxic cumpounds. Each class has precautlonary measures for safe storage according to its nature. Acids, for example, can react with metals and metal hydrides to emit flammable hydrogen gas. The heat of reaction may be eno"gh 6 ignite the gas and cause a fire or explosion. Contact of acids with iron sulfide or sodium cyanide is extremely since lethal gases are generated. Since most acids are corrosive to matter, provisions should he made to contain unexpected leakage. The simple use of a chemical-resistant tray can solve this problem (Fig. 6). A list of storage classes follows with precautionary measures for each class. ~
~
~
.~~
.
Store large bottles on low shelves or in a c ~ d cahinpto. Segregate acids from active metals such as sod~um.potassium, magnesium. etr. Segrrgare oxidizing arid* frum organic acids. flammable and combusrible materials.
Keep away from any source of ignition: heat, sparks, or open flames. Oxidizers Store in a cool, dry place. Keep away from combustible and flammahle materials. Keep away from reducing agents such as zinc, alkaline metals, and formic acid. Water Reactive Chemicals Store in a cool, dry place away from any water source. Have a Class D fire extinguisher available in case of fire. Phyrophorie Substancb Materials which will react with the air to ignite when exposed (e.g., white phosphorus). Store in a cool, dry place making provisions for an airtight seal. Light Sensitive Chemicals Store in amber bottles in a cool, dry, dark place. Peroxidizable Chemicals Store in airtieht containers in a dark. cool. and dry piace. Label containers with receiving, opening, and disposal dates. Periodically test for the presence of peroxides. Data that identify the reactive class for a chemical as well as its incompatibilities are available from a number of sources. The label on the bottle itself will normally identify whether the chemical is an oxidizer, flammable, water reactive, etc., and provide warning statements as to reactivity. A Material Safety Data Sheet (OSHA 20 form) normally gives reactivity information for a specific chemical and has an entry for special precautions to he taken for storage and handling. availahle from mast manufacturers. L. ~ r e g e r i c k s"Handbook ' of Reactive Chemical Hazards" 2nd Edition (cited in Fig. 7) is a comprehensive volume of individual incompatibilities and reactive hazards. An in(Continued on page A1621
V0l ume 59
Number 5
May 1982
A161
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