I
in the Chemical Laboratory
XXXIV.
Edited by N O R M A N V. STEERE, School o f Public Health, University of Minnesota,
Instrument and Equipment Hazards' E. A. Wynne, Grace Mary Ederer, Barbara Tucker, and N. V. Sleere
Safe operatiotl of labomtoly instruments and equipment depends on buying or Imilding apparat>ls with adequate controls and safegtml.ds, installing the nppnlatm in safe lorations wit,h necessary veutilation, m d using the ~ppnrat,us within the limit.at.ions of the original design or applnpriate modifications. Ft.artimr culleetors provide one example of apparatus which haa caused serious hnmrds when used in operations different than those for which the colIeeto~r were oliginally designed. Most fraction colleetot.s were designed for use with aqueous solvents, hut serious fires have rewlted when flammable solvents were used in the same apparatus and vapors ignited by open electrical eontacts. The Forest Products Laboratory in RIadison, Wis., salved the problem hy adding a small exhaust fan to remove slrlveut vapors-when the ttansport mechanism jammed m e night t,here was no aeeumulatiotr of solvent and i ~ r ,fire. While eommereinlly available instruments and lahoratu~y eq~iipment will generally he safer and more relinhle t,han laboratmy-bldt devices, safet,y in design and operat,ion is not always considered ur given adeq1lat.e attention. A conmon exan~ple of haza~lloous isborntory equipment bhat is not usually provided or purchased with t,he minimnm safeguald is the vacuum pnmp or compressor with an exposed helt-a device that can surprise hy catching a lah coat or injure Ily cutbing OR fingers. Belt gnmds can he pwchased, or fabricated, even thoogh they are not provided as Lxndnrd eqnipmeut on pumps bee~nse of competitive bidding. If Inborntory equipment or instruments ope!.ate nt high voltages, high pressures, high speeds, or high temperatures, there is a particular need for guarding against the hazards that may injure persons using o r working around the devices. A recent deabh from a high voltage device is a case in point,. (Science 153: 1721-23, 1966). Electrical and other safety standards have been established for several types of laboratmy eqnipment and it is possible to specify purchase of equipment which has been tested and labeled by such atio ion ally-recag~~ized test,ing lxbaratories xs Underwriters Laboratvries, Inc., Factory hhtuual Laboratories, and Underwriters Laboratories of Canada, Inc. Some of the types of laboratmy equipment which are lisbed and labeled as meeting safety tests of the Underwriters Laboratories, Ine. are:
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Bench lights Colony counters Furnaces Emergency lighting equipment Explusion-proof xppliancps for haaardmls Inenlions Ileate~x Not ~ h t e s Incrlh~tors Ovens Stirrers Water haths Shakers A performance evaluabion program for new instl.uments for clinical laboratories has heen proposed by Bradley E. Copeland, hI.D., of the Commission on Continuing Education of t,he Amerirnn Soeiet,y of Clinical Pathologists, a t New Ihiglnud Deaconess IIospital in Boston, RIass. (Journal of lhe Associalia ,for the ridt,aneemenl o f nlcdical Inslnrutenlulion, 1 (no. 1): W-31, 1!166). Instrument evnluations have been invited for an I n s t ~ w n e n tEvaluation Registry by Matthew Patton, M.D., Chairman of the Bnbcommittee on Instrnments of t,he Standards Committee of the College of Anleriem Pst.hologists, which has prepmed the pnmphlot,, "A Suggested Guide for Mnuufactrmrs fvr Preparation of Rlanoals of Operation for Laboratory Instruments." Dr. Pat,ton is a t Sacred Heart (;enera1 1Iospit.d in Eugene, Ore. Technical literature should be obtained from manufacturers prior to pu~chming instruments or equipment, and most companies will oblige with schematim of their items. All will supply operating instrwtivns. I t would be wise to study the schematic diagram so that a. good indieat,ion can be ohtained as tu usefulness of the item in teaching or research. After instruments or equipment are purchased, dhere should he a checkout prooedure using the operating instmctions. A good axiom in using equipment is to observe its limitations and not force or employ it for work for which it was not designed. Following is a list of heasrds and safeauards which should be considered in purchasing, setting up, and using laborntory equipment. This list is not complete, and should be added to as further experience is reparted.
Instruments Using Gas from Cylinders or Piping Systems Use of gases, pressure bottled or piped, requires normal precautions for deter-
'Prepared for the "Hmdbo?k of L a b q r e t o ~ ySafety," in preparation by T h e chemical Rubber Co. printed with thew p e m s s m n .
E. A. Wynne received his B.9. degree i n Chemistry at Ohio Univemity, Athens, Ohio, in 1933 and his 1I.S. degree in Chemistry (.4nnlyticnl) nt Vanderhilt University in 1034. He is presently employed s t Fisher Seienlific Co., as Senior Research Chemist. He is n member of t,he New Jersey chapter of the American Society of Safety h g i u e e m . He is Safety Edilor, The Indicator, N. Y. and Sort,hern N. J. A('S Joarnni. He is a Fellow of the American Institnte of Chemists, pa-t chairman of the N. Y. chapter, and the American Association for the Advancement, of Science. He is also a mumher of the Kew Ymk Academy of Science and Alpha Chi Sigma. Grace Mary Ederer, h I T (ASCP) i~ assistant t,o the Director of Clinical Laboratories, University of Alinnesot,a Haspitnls and Assistant Professor of 3ledicd Technology. She roeeived her B.A. degree s t the College of St. Q~therine, St. Paul, Alinn., in 1941 and her 1I.P.H. degree a t t,he University of Mirlnesuta in 10W. Barbara Tucker, h l T (ASCP) is Chief Technologist w d Teaching Supervisor a t Northwestern Hospital, Minneapolis, Minn. She received her B.B. degree in lledical Technolugy s t the U n i v e d y of Minnesota in 1944. mining positive closure of all fittings to prevent leaks. The list below will help in determining safety check points on equipment snch as flame photometers, automatic analyzers, spectmphokrneters, and similar equipment. Adequate safegortrds to prevent inadverlent ignition. Suitahle check valves to prevent gases from surging back into gas line. Flame arrestors, where necessary, to prevent flash back of flame int,o gas lines. Purchase or use of fuel and combustible gas cylinders, within the maximum size and qnmtit,y limits established by locd fire authorities, particulsrly iu hospital iaborstories. Equipment for holding gas cylinders stable should be required and used wit,h equipment requiring gas cylinders. Gas-tight fittings and hoses rated for t,he application, if permanent piping is not practicable. P~.eswre limiting devices to prevent overpressure to the system. Dnrable and appropriate piping or tohing*.g., no oil in oxygen lines, no copper in acetylene lines, gas hoses provided to meet service speeificstions, ete. Atomic absorption spectrophotometers in parbieular need to have suitable e x h x u t conneotions to prevent buildup in work areas of hazardous concenbratio~~sof (Continued on page Al40)
Volume 44, Number 2, February 1967
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A1 39
Safety
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toxic gases, vapors, or fumes emerging from the flame unit. Flames should be guarded by built-in shields which will sttentuste any explosion, eruption, or injurious radiation and protect the person using the equipment.
Centrifuges In selecting a centrifuge, carefully consider location, type, and use. If 8 tabletop type is acquired, make certain that it is securely anchored. Instruct sll wers an the importance of balancing each time the centrifuge is used. Other irnportmt check points me: Adequate shielding against accidentd "fly-swaysn--double wells provide greater pr0tectiOn. Prevention of "walkine." -. with suction cups or wheel brakes. Accessibility of parts, particularly for rotor removal. Top equipped with disconnect switch which shuts off rotor if top is inadvertently opened. Safeguards for handling flammables and pathogens, including positive exhaust ventilation, to a safe location from which recirculation is very unlikely. Positive locking of head. Electrical grounding. Location where vibration will not cause bottles or equipment to fall off shelves.
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Ovens, Furnaces, Hot Plates, Mantles, and other Heating Equipment Caution personnel to use asbestos gloves and tongs when placing or removing samples into or from ovens, furnaces, and hot plates. Mantles should be used only with suitable variable powemtats so that rated wattage is not exceeded; if a higher wattage heater is necessary, a higher rating should be provided rather than using the full input of the powerstat. Blow-out panels or magnetic latches. Latches are more desirable if they open a t pressures just above 1 atmosphere. Forced draft, well designed convection, or inert gas purging to prevent explosive concentrations. Controls marked in definite units. Reliable and well-maintained thermostatic controls. Double controls for use with hazardous materials. Explosion-proof contactom, controls, and switches for equipment to contain or be used in potentially explosive atmospheres. Controls which fail on the safe side. Higher wattage ratings provided by design for 220v. rather than 110v. Electrical grounding of all exposed metal or electrically conductive cabinets and parts. Sealed thermostats to prevent possible ignition of flsmmable solvents. On-off switch with pilot light is a must for hot plates. Hot plate wiring should not be exposed.
Hot plates should he designed for laboratory use (not the hardware store type) to prevent hot spots. Electrical controls on mantles should have thermostats to prevent excessive heating. Facilities for an inert gas purging of mantles in case of spillages. Bright indicator light on heating e q u i p ment with time switches, to show when equipment has been set to turn on later (intentionally or inadvertently).
Electronic Equipment Select equipment adequate for the uses for which i t has been designed. Always fallow msnufacturers' directions for installation or request the manufacturer's technical representative to install e q u i p ment. Plan to acquire and use proper protective glasses where ultrwiolet fluores cent equipment is to be used. If x-ray, neutmn activation, or similar processes are employed, insure that personnel me instructed in the hazards of stray r a d i e tion.
transformers. Clear distinction between instrument circuits and building electrical circuits. A desirable safety feature would be the introduction of s, double pole-switch and/or s polarized or keyed system to prevent insertion of a n improper plug. Electric motors and controls should he chosen for specsed jobs: explosion-
Safety
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proof for use with flammables, etc.1 nonexplosion-proof types for general use. Equipment should be fused, and have under-voltage protection in event of s. partial power failure. Equipment should have a. combination of magnetic and thermostatic branch circuit protection. Lamp holders and switch terminal insulation should be ceramic, psrticulsrl~~ where used in locations of h ~ p hrelative humidity. Powerstats should be properly shielded and suodied with built-in fusine. ~ e k i e r a t u r elimit switches'should be provided to prevent overheating. Electrical immersion heaters should he protected against overheating through failure of the~mostaticcontrols, by use of an automatic cut-off and by a low water level cut-off. Personnel using fluommeters should wear protective glasses to prevent injuly from stray ultraviolet radiation. Gas chromatograph electronics should be insulated-particularly the "hot" side. Gas chromatographs shodd be ventilated adequately. All cords for heating units should have insulation approved by Underwriters Laboratories, Ine. X-ray equipment should be shielded to prevent stray radiation. Neubron-guns should have built-in shielding and adequate directions for use. Lasers should be well protected to prevent shock, accidental discharge, and stray radiation.
Miscellaneous Pressure release eontmls should be provided for opening autoclaves. High-pressure types of autoclaves should have adequate explosion protection, and all controls should be of the remote type so the operator can he behind a protective wall. Calorimeter hombs should he adequately shielded as protection against. explosions. Safety shields required for equipment should be sized and designed to provide adequate coverage, stability, a n d resistance to penet,ration and convenience of use. Microtomes: positive lock to prevent unexpected operation; guard to keep operat,ors' body parts out of t,he path of long knives which may project beyond the sectioning area. Fraction collectors: ventilated to enhaust leaks or spills of flammable liquids which may be used; explosion-proof construction if possihle or design to keep ignition sources out of area where fliimmable vapors may accumulate; conridel. location in an area or enclosiue where the fire damage potential will be minimized: signal to indicate cycle completion. Tissue processors: (e.g., Auto-Tecbnioon or Tissuemclton): consider location in a separate room or closet with special exhaust ventilation, and with curbing
(Continued on page A1493
Safety
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t o confine any spill of the flammable liquids used in the eqnipment. Paraffin dispen5et.s and vacuum illfiltmtnla for parafin: aulomatic overtemperat,nr.e shut,nR in series with t h e c mostatic control so that t,hermostat failure will not result in overheating and fire. Electrophoresis apparatus: proper grounding and electrical intet.locks are necessary to prevent personnel from p o s sible contact with any voltages which could cause shock or death. Chlamntography equipment.: carefully cont,rnlled ventilation to remove any excess or air-home vapors that are toxic, narcotic, irritating, or a ni~isnnce. Exressive enhanst rates on ehromatagr~phy jars will cause temperature diffet.ent,idls that introduce gross errors hy alteration of migration rates. Equipment for distillation, sane melting, and similar equipment to be used on a cont,inuous rml should have "fail-safe" attachments to orevent 4erious consequences in ease oi water pressure changes or electrical failure. Reirigerators: Many l ~ b u r a t o r y explosions have resulted when ordinary domest,ic refrigerators have heen used for storage of flammable liquids and leaking vapors have reached one of the many ignition sources within such refrigerators. One means of preventing such explosions has been twofold: t o mark all ordinary refrigelatom a s unsuitable for flammable
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liquid storage, and where such st.orage is necessary, to modify ordinary refrigerators by removing all light,s, switches, heating units, open thermostats, and at,her ignition sonrces. One university has adopted standard purchase specifient,ions requiring weh modilicatians by suppliers of roirigerators for laboratories. h o l h e r means oi preventing ref~.iger-etor explosions has been the development of explosion-proof refrigerators hy bhme manufacturers. Such refrigeralors are teskd and list,ed as explosioii-proof bjUnderwriters Labo~atories,Inc. and the entire refrigeratur would he safe in most explosive atmospheres. A question re mains whet,her t,he expense of soch explosion-proof refrigerabors is justified in lnboratories where bhele m e many sources of ignition and very few pieres of laboratory equipment can be porchnsed that are explosion-proof. Environmentnl chambers, i r ~ c u h i t t ~ w and walk-in coolers: walk-it, coolem, incubators, and environmental chambers should be equipped so that persuns cannot he trapped inside, so that persons inside can signal a n emergency and summon help, and so that toxic or flammable concentrations can be prevented by regular or special means. Even in cold chambem i t is practicable to provide routine exhaust ventilation to prevent development of hazardous atmospheres from normal activities in the chamber. Standard equipment for cold moms a t one university inclrtdes inside alarm signals and gasket heaters to prevent. doors freezing shut.
Summary h I m y of the precaut,ions list,ed hele may heeome nnneeessary a. the makers nf scientific apparatns impmve desig~l and bnild in snfegonrds in response to demand and t,he specific reqoiremeuts oi users. The precaut,ions and safeguards rerommended here for purchasing, insballing, and using instruments and equipment are not inclusive and the ~ ~ l t linvite l ~ r l'ep01'18 ~ nf experience with new eouinment. and wibh new uses of . . erist,ing equipment.
Coming Soon in book form
SAFETY in the Chemical Laboratory All the articles in this column from their inception January 1964 through January 1967 will he reprinted in our paperback series. These articles will be grouped by subject matter. Also included will he all the accident case histories.
Publieation date, approzimately March 1, 1967. Pwbable priee, 83.W
