APPu1F MIcRomowOy, Mar., 1967, p. 378-389Copyright 0 1967 American Society for Microbiology

Laboratory Design for Microbiological SafetyG. BRIGGS PHILLIPS Am ROBERT S. RUNKLE

Communicable Disease Center, Atlanta, Georgia, and National Cancer Institute, Bethesda, Maryland

Received for publication 7 November 1966

Of the large amount of funds spent each year in this country on construction andremodeling of biomedical research facilities, a significant portion is directed tolaboratories handling infectious microorganisms. This paper is intended for thescientific administrators, architects, and engineers concerned with the design of newmicrobiological facilities. It develops and explains the concept of primary andsecondary barriers for the containment of microorganisms. The basic objectives of amicrobiological research laboratory, (i) protection of the experimenter and staff,(ii) protection of the surrounding community, and (iii) maintenance of experimentalvalidity, are defined. In the design of a new infectious-disease research laboratory,early identification should be made of the five functional zones of the facility andtheir relation to each other. The following five zones and design criteria applicableto each are discussed: clean and transition, research area, animal holding and re-search area, laboratory support, engineering support. The magnitude of equipmentand design criteria which are necessary to integrate these five zones into an effi-cient and safe facility are delineated.

The magnitude of the annual national invest-ment in new biomedical laboratory facilities,coupled with the problems arising out of unsafedesigns in these facilities, justifies increased atten-tion to engineering design criteria to maximizemicrobiological safety. A number of recentpapers, conferences, and seminars have dealt withone or more aspects of microbiological laboratoryplanning and design (3, 15, 16, 20, 21).

Incorporation of microbiological safety meas-ures in the design of biomedical laboratory facili-ties is needed for one or more of the followingreasons: (i) to prevent the uncontrolled escape ofinfectious materials from the building to safe-guard the health of the surrounding community;(ii) to assist in the prevention of accidentallyacquired infections among building personnel;(iii) to prevent the unintentional spread ofdiseases among animals by animal-to-animal orman-to-animal transfer; and (iv) to prevent falselaboratory results due to cross-contamination ofmicrobiological cultures.The purpose of this article is to describe and

illustrate some of the principal building featuresand devices used to provide effective microbialcontainment for accomplishing the above aims.The article is a corollary to a movie with the sametitle that has been made by the Public HealthService Audiovisual Facility and sponsored by theNational Cancer Institute. The film may be bor-rowed free of charge from the Public Health

Service, Communicable Disease Center, 1600Clifton Road, Atlanta, Ga. (Laboratory Designfor Microbiological Safety-M-1091, 16 mm,sound and color, approximately 35 min).The initial step that should be taken in the de-

sign process for a microbiological research labora-tory is an analysis of the research activities to beundertaken, the hazards associated with the re-search and with each operation, and a functionalevaluation of the relationships that will existbetween each activity. This analysis should enablethe laboratory director and the architect or en-gineer to estimate the extent of the hazardousoperations and to concentrate and minimize theamount of containment equipment required,thereby realizing economic savings.

Determining what safety measures to in-corporate in the design of infectious-diseaselaboratories has required much research andstudy. For instance, it was necessary to under-stand how laboratory workers become infected,how microorganisms might escape and spreadwithin a building or escape to the surroundingcommunity, how animal cross-infection and cul-ture cross-contamination occurs, and other simi-lar problems (6, 10, 12). From the results of anumber of laboratory hazards studies (1, 9, 17,18), two concepts emerged that have proved suc-cessful in designing biologically safe laboratories.The first is the concept of primary and secondarybarriers for the laboratory containment of infec-

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woter bottle,

FIG. 1. Safety cabinet (upper left); ventilated animal cage (upper right); safety centrifuge cup (lower left);safety blendor bowl (lower right).

tious materials, and the second concept providesthe designer a logical division of major functionalzones within a typical laboratory building.

Primary-secondary barrier concept. Enclosures,barriers, or other containment devices that im-mediately surround the infectious or potentiallyinfectious material are designated as primarybarriers. These are the first line of defense (otherthan the test tubes, flasks, etc.) for preventingescape and possible spread of infectious micro-organisms. Examples of primary barriers areventilated microbiological cabinets, closed venti-lated animal cages, closed centrifuge cups, andsafety blender bowls (Fig. 1).

The secondary barriers in a laboratory are thefeatures of the building that surround the primarybarriers. These provide a separation between in-fectious areas in the building and the outsidecommunity and between individual infectiousareas within the same building. Examples of sec-ondary barriers are (i) floors, walls, and ceilings,(ii) ultraviolet (UV) air locks and door barriers,(iii) personnel change rooms and showers, (iv)differential pressures between areas within thebuilding, (v) provisions for filtering or decontam-inating potentially contaminated exhaust air,and (vi) provisions for treatment of potentiallycontaminated liquid wastes. These and other sec-

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SECONDARY BARRIE

FIG. 2. Primary- and secondary-barrier concept.

FiG. 3. Five functional zones ofhypothetical laboratory.

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ondary barriers provide supplementary micro-biological containment, serving mainly to preventthe escape of infectious agents if and when a fail-ure occurs in the primary barriers. Figure 2 is agraphic representation of the functions of primaryand secondary barriers.

Actually, the more effective the primary bar-riers are, the less need there is for emphasis onsecondary barriers. Therefore, during the designphase of any infectious-disease laboratory, it isboth important and economically necessary firstto determine and select the primary containmentdevices to be used, thereby reducing thecomplexity and cost of the secondary barriers.

Functional zones ofa laboratory building. Figure3 illustrates five functional zones of a hypotheticallaboratory building for research with infectious-disease agents. Obviously, there can be numerousphysical arrangements of these zones, but thetypical arrangement shown will illustrate theirrelationship to each other and provide a basis fora discussion of the design requirements for micro-biological safety.

Clean zone. The clean zone of a laboratorybuilding (Fig. 4) contains the entrance area, theoffice area, conference room and library, andthose functional rooms where administrativeoperations, conferences, reading, writing, andother tasks not involving infectious materials arecarried out. Also, within this zone are the transi-tional rooms through which personnel and ma-

Clean Office

reception area

Entry * Clean Corridor

terials enter and leave the potentially infectiousparts of the building. These transitional roomspreserve the integrity of the secondary barrierwhen people and materials enter and leave theinfectious areas.!In addition, the necessary ship-ping, receiving, and clean storage areas are in theclean zone. The mechanical equipment space, al-though a clean area, will be discussed below.

Personnel should enter and leave the infectiousareas through clean and contaminated changerooms, illustrated in the lower right hand portionof Fig. 4. The clean change room should providelockers to store street clothing, storage shelves forlaboratory clothing, and appropriate toilet andwash facilities. An air lock with a UV doorbarrier and ceiling-mounted UV lamps separatesthe clean from the contaminated change room.Adjacent to this or between the two change roomsshould be located a shower room for use whenleaving the infectious areas. The contaminatedchange room should contain a storage rack forlaboratory shoes, a bag for discarding laboratoryclothing upon exit, and suitable toilet facilities.The use of UV lamps in the shoe storage rackand clothing discard bag can be an effectivesecondary barrier (11, 19).

Transitional arrangements for materials andsupplies generally are needed at two locations. Atthe front of the building, provisions are usuallyrequired for transferring books, data sheets, andsimilar items between clean offices and offices in

Clean Chonge Room Contaminated Change Room

FIG. 4. Clean zone, clean and contaminated change rooms.

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the infectious area. Typically, this may include asmall through-the-wall ethylene oxide gas cham-ber for the cold sterilization of heat-sensitive ma-terials (8) and a UV apparatus for decon-taminating sheets of paper passed out of the in-fectious area (13), as illustrated in Fig. 5.Transitional rooms at the rear of the laboratoryare needed for receiving laboratory and animalroom equipment and supplies and for removingequipment, trash, and other items from the in-fectious areas. A typical arrangement (Fig. 6) atthe rear of the building will consist of a UV airlock for the inward passage of supplies, and cleanand contaminated receiving rooms separated by

Clean Corridorf Clean Off ice

t Contominated OfficeContominoted Corridor

FIG. 5. Transitional arrangements between clean andcontaminated offices.

Confornmnoaed Svues Clean ReceivIng Area

supplIes to,. -coeaninarted

doors nterlocied sui iesU ucao,rlock

gos or steom ajpoclovse

equipment to laboratory _supporl zone _ lorge cage rack or equipment

\Rear of Building

FIG. 6. Transitional arrangements between cleanreceiving area and contaminated research area.

large through-the-wall autoclaves that are alsooperable with mixtures of ethylene oxide gas. Theuse of small viewing windows and speaking dia-phrams facilitates communication and operationin the front and rear transitional rooms.

Laboratory research zone. The laboratory re-search zone (Fig. 7) contains laboratories for in-fectious microbiological operations, exclusive ofanimal work. This zone is separated at least by acorridor from the zone where infected animals areused. In addition to laboratory rooms, this zonemay contain potentially contaminated offices ad-jacent to offices in the clean zone, necessary toiletsand change rooms, constant-temperature roomsfor incubation and refrigeration, and instrumentrooms for centrifuges and other research appara-tus.One of the most important tasks in planning the

laboratory research zone is the selection of theprimary barrier ventilated cabinets. Althoughcabinets are available in many shapes and sizesand constructed of a variety of materials, there areonly two basic types: partial-barrier cabinets andabsolute-barrier cabinets. Figure 8 shows apartial-barrier cabinet that provides an inwardsweep of air through the open panel and awayfrom the operator. This unit may also be used witha panel and gloves attached as shown in Fig. 9.Absolute-barrier cabinets are similar in appear-ance (Fig. 10), but are gas-tight and are operatedat a constant negative air pressure. The selectionof partial- or absolute-barrier cabinets will havea significant effect upon sizing of the air-handlingequipment because the former require 300 ft3/minsupply and exhaust, whereas the latter requireonly 3 to 10 ft3/min per 6-ft unit. Obviously, theselection of the types of cabinets for use with theinfectious cultures will vary according to anassessment of the risk of the types of laboratoryoperations together with the particular micro-organisms to be used. In reference to the hy-pothetical laboratory research zone (Fig. 7), it isassumed that 75% of the research area will be forlow to medium risk work requiring partial-barriercabinets, and 25% will need to be equipped with

Clean Office Contaminated Office

FIG. 7. Laboratory research zone.

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absolute cabinet systems for performing high- -_hazard operations. The absolute cabinet systemterminates with a double-doored autoclave, anda germicidal liquid bath is also available forpassing materials in and out of the system. Atleast some of the other laboratory rooms should....have free-standing, single-door autoclaves. ThisXl..reduces the need to transport potentially infec-tious materials in the corridors. In determiningspatial arrangements for safety cabinets and themost effective and efficient room sizes, the bench

FIG. 10. Absolute-barrier safety cabinet system.

concept developed by Norman (7) is appropriate,except that the cabinets replace the open bench inmany of the activities.Within the laboratory research zone, there are

a number of design considerations that will di-rectly influence the containment by the secondarybarriers. The most important of these are asfollows.

(i) Microbial filtration of non-recirculated airexhausted from the laboratory rooms. High-efficiency microbial filters (2) with 99% retentionof 1.0-,u diameter particles usually are appro-

|............ priate.(ii) Microbial filtration of exhaust air from

absolute-barrier safety cabinets and other ap-paratus where aerosols of infectious microorgan-isms are intentionally generated. Ultrahigh-effici-ency filters (2) with 99.95% retention of 0.3-,udiameter particles are acceptable in these appli-

FIG. 8. Partial-barrier safety cabinet. cations. In some instances, it also may be desirableto utilize an electric or gas-fired air incinerator inaddition to the ultrahigh-efficiency filter for ulti-mate protection.

(iii) Air pressure balance within the zone shouldmaintain the laboratory rooms negative to ad-

- _ ~ joining halls, and the cabinets negative to thelaboratories. Differential air pressures are estab-

/s_ , _ ^^ < lished by controlling the direction of airmovement. A typical laboratory may be main-

tv s ___tainedat a pressure negative to surrounding areasby exhausting larger quantities of air than aresupplied. Obviously, the balance of such a system=iPX, can be significantly affected by the pumping ac-

- ^ w _vtionof doors, traffic, and other factors. The entire-1i_Loi laboratory research zone should be maintained at........°.ik__RE_ a negative pressure compared to the noncon-

taminated zones.(iv) Paints and coatings used on walls, wall

FIG. 9. Partial-barrier safety cabinet, gloves attached. curbings, ceilings, floors, and other surfaces must

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be resistant to flowing steam and to the disinfec-tants used in the decontamination process andfrequent washings. Walls, wall curbings, andceilings should be free of cracks, and the coatingsflexible enough to span minor shifts in the struc-tural system. A monolithic covering is often usedon the floors.

(v) Casework and other installed equipment,when possible, should be sealed to floors and wallsto limit possible spread of contamination. Equip-ment not sealed to walls or floors should bemovable or mounted on wheels to facilitate de-contamination and cleaning.

(vi) Lighting fixtures, pipes, conduit, and otherservices that penetrate the secondary barrier wallmust be designed and installed to preserve thebiological separation between the contaminatedand clean zones. Electrical conduit should beinternally sealed. Fixtures should be sealed to thewall or ceiling or mounted away from the surfacefor ease of cleaning.

(vii) To limit personnel traffic, liberal useshould be made of viewing windows and speakingdiaphrams in doors or walls to laboratories, par-ticularly doors to walk-in refrigerator and incuba-tor rooms.

(viii) In some rooms it may be desirable to in-stall ceiling-mounted UV fixtures operated fromthe corridor when the room is unoccupied. Thesefixtures aid in reducing nonspecific microbial con-tamination and are useful in case of an accidentalspill of infectious material.Animal research zone. When the animal research

zone is used for relatively small laboratory ani-mals, the rooms are usually located in the samebuilding as the laboratory research zone. Thiszone typically includes rooms for animal inocu-lation and autopsy, and infected-animal holdingrooms equipped with primary-barrier isolationequipment such as ventilated cages and UV cage

Cleor Co- do Contarm oted Corridor

racks (Fig. 11). In some instances it may be de-sirable to locate aerosol exposure equipment, suchas the Henderson apparatus, in a room adjoiningthe animal room.

If not available elsewhere, the animal areashould have an incinerator for disposing of animalcarcasses, and a large autoclave for sterilizingcages and passing them into a cage-washing room.

In designing this zone, the type and degree ofanimal isolation should receive early considera-tion. It should always provide for safe workingconditions for personnel and prevent undesiredanimal cross-infection. The caging system selectedwill affect the cost of the facility, and ventilatedcages will have an impact upon the size of theair-handling equipment.Dust filters should be installed at the air exhaust

ducts of the animal rooms to prevent excessiveloading of the downstream microbial filters withanimal hair and dander. It is desirable to havethese filters decontaminated in situ and changedby laboratory personnel. The recommended mini-mal ventilation rate (Guide for Laboratory Ani-mal Facilities and Care, rev. ed., Public HealthService Publication 1024, Washington, D.C.,1965) for the rooms is 15 changes per hour offiltered, nonrecirculated, draft-free air of the rela-tive humidity and temperature appropriate to theanimal species. Since the walls and floors of ani-mal areas will be decontaminated and washedfrequently and exposed to urine and other wastes,careful selection should be made of wall paintsand finishes.

Other design considerations of importance inthe animal zone are: waterproof lighting fixturesin wash areas, floor drains, adequate storageareas, cage- and rack-washing equipment, auto-mated animal care activities, etc. Although thenature of some disease agents in small animals issuch that no special provisions are needed to pre-

,1 Conta ml noted An,Imol Roomst

FIG. 11. Small-animal research zone.

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vent cross-infection or to protect animal handlers,many infectious agents require animal isolationequipment for protecting personnel. In situations t,where a high degree of isolation is required andwhere animal-to-animal separation is needed, in-fected animals are held in small, individuallyventilated cages (Fig. 12). In some instances, in-stead of closed ventilated cages, animals may behoused in cages under a UV barrier (14) as illus-trated in Fig. 13. Nonportable ventilated animalcompartments have been found to be effective insome infectious-disease laboratories. Each of the

FIG. 14. Modified Horsfall isolation cages.

Horsfall units (5) shown in Fig. 14 holds one ortwo animal cages and is equipped with a viewinwindow and inlet and outlet air filters.

If the animal research zone uses infected large4animals, such as horses and cattle, it may be in aremote wing or suite, or may even be located in acompletely separated facility. In any case, sinceit is very difficult to provide primnary barriersaround large animals, greater emphasis is or-

FIG. 12. Ventilated animal cage rack (with UV dinarily placed on the secondary baffiers. A typi-screen). cal suite for housing infected large animals (Fig.

15) would contain holding rooms with movablestanchions and partitions, and rooms or areas foranimnal inoculation, surgery, autopsy, and inciner-ation of carcasses. In case the epizootic diseases

~~~~being studied are transmissible to man, protection- ~~for operating personnel must be provided by

- ~~~~~~~~~protective garments and respirators or ventilated- ~~~~~~~~~~~suitsif needed. The large-animal zone should have

change rooms and transitional rooms for move-ment of food and equipment as previously de-scribed.

.._._

Laboratory support zone. In many infectious-disease laboratories, the zone for laboratory sup-port is best located outside the contaminatedresearch zones. From an economicandiftnctionalstandpoint, this location reduces the amount ofsecondary-barrier area required and provides anopportunity for grouping similar support func-tions in one area. An admitted disadvantage oflocating the laboratory support zone outside thecontaminated research zone is that washroom andanimal-room personnel cannot move between thecontaminated and clean zones without changingclothing and showering, and therefore additional

FIG. 13. Nonventilated animal cage rack (with UV personnel may be required.screen). A typical laboratory support zone (Fig. 16)

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may include rooms for washing and sterilizingglassware and animal cages, preparing culturemedia, storing equipment, glassware, and animalcages, and repairing various laboratory items. Insome instances, the support zone may containanimal rooms for the quarantine and acclimatiza-

tion of animals before they are passed into theinfectious area for use. Careful attention must begiven to the design of the ventilation system forthis zone because of the many heat-generating andodor-producing procedures which are carried outin the washing area. Also, because of the large

overhead monorail

incineratofroom

FIG. 15. Large-animal research zone.

FIG. 16. Laboratory support zone.

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amount of water involved in washing operations,floors, walls, and other surfaces should be resist-ant to moisture. The room for culture mediapreparation should have a controlled movementof filtered supply air. To limit the ingress of micro-organisms, air in the room and cabinetry alwaysshould be maintained at a positive pressure com-pared to the other laboratory support rooms.

Engineering support zone. The fifth functionalzone provides engineering support for the entirefacility. Included here are the necessary pipes,ducts, pumps, blowers and filters, the liquid wastetreatment system, and most of the air-handlingsystems. Special engineering arrangements shouldmaintain the integrity of the secondary barrierwhen penetration of the wall is made by pipes,wires, and ducts. As much of the engineering sup-port equipment as possible should be locatedoutside contaminated zones, to reduce the neces-sity of entrance of maintenance personnel. Thezone can be comprised of space located on thegrounds adjacent to the building, or in the attic,basement, or other building space. Because of thelarge amount of engineering equipment needed,as much as half of the total building area is some-times required for this zone.The equipment required to heat, cool, filter, and

distribute the supply and exhaust air for thevarious building zones will occupy a large part ofthe engineering support zone. This equipmentmay represent an investment amounting to nearlyone-half the cost of the facility.Whenever a device or item of equipment is

essential to the maintenance of a microbiologicalbarrier and is subject to failure, "fail-safe" designfeatures are required. This aspect should be ac-complished through the use of redundant fansand motors, interlocked supply and exhaust fansto prevent pressurization of infectious areas,emergency electrical generators, filters in serieswith air incinerators, automatic cycling of auto-claves after the door on the infectious laboratoryside is opened, etc. The inclusion of such itemsin a laboratory should be determined only afteran assessment of the risks associated with theresearch activity has been made.One vital consideration is the need to locate the

air-intake grille upwind of the exhaust stack. Inaddition, there should be adequate physical separ-ation between both to prevent cross-contamina-tion. In the engineering support zone, air ductsgoing to each room in the infectious zone shoulddeliver non-recirculating, filtered, and conditionedair.The supply ducts need not be of air-tight con-

struction, but exhaust air ducts coming from theinfectious zone must be air-tight to assure noleakage of infectious microorganisms before the

air reaches the exhaust filter plenum. Galvanizedducts with taped, epoxy-coated joints have beenfound satisfactory.

Exhaust air plenums are often sized to serveseveral laboratory rooms of about the same haz-ard level. They may be equipped either with high-efficiency spun-glass mats, or with ultrahigh-efficiency units for filtering air discharged fromthe rooms. Because the filters in a plenum must bechanged periodically, provisions should be madefor decontaminating both the filters and theplenum itself before entry by maintenance person-nel. A mixture of steam and formaldehyde isfrequently used as the decontaminant (4).

In virus laboratories, inlet air is often passedthrough ultrahigh-efficiency filters. This high-quality air is required to prevent accidental con-tamination of experimental cultures by endog-enous organisms or by other organisms utilizedin the research program. In tissue culture cubiclesor other areas requiring this high-quality air sup-ply, the use of a high-volume recirculated airsystem with ultrahigh-efficiency filtration shouldbe considered if no hazards to operating personnelare created. This system will result in significanteconomies by reusing conditioned air, and will beacceptable if proper separation by zones of similarusage is employed.An important part of the engineering support

zone is the central control board (Fig. 17). Here,read-outs of all systems in the area can be moni-tored by engineering personnel. Such boardsshould have visual and audible alarms that willautomatically signal the failure of any part of thesystem when preset limits of environmental fac-tors such as temperature are exceeded. Anotherimportant item is a standby electrical generatorthat is used in the event commercial power supply

FIG. 17. Central engineering control board.

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is interrupted. Although it may not be possible toprovide a generator large enough to supply fullelectrical requirements, the standby currentshould at least be sufficient for ventilated animalcages, ventilated cabinets, deep freezes, refrigera-tors, incubators, and emergency lighting. Thestandby units may be mounted in trailers to pro-vide easy portability, or incorporated in the en-gineering support zone.

In some laboratories, facilities must be pro-vided for treating contaminated liquid wastes.Two basic systems are usually employed: batchand continuous flow. However, if the hazardsassociated with the program are minimal andadequate space is available, a sanitary drain fieldcan be utilized. Regardless of the system, in thelaboratory no infectious culture fluids should beknowingly poured into drains without priorsterilization.The batch system (Fig. 18) is used to collect

potentially infectious effluents from infected ani-mal areas by gravity flow. When a tank is aboutone-half full of liquid, the drain lines are closed

FIG. 18. Batch-type liquid waste treatment system.

FIG. 19. Continuous-flow waste-treatment system.

and the liquid is sterilized by adding steam andholding for a period time. Usually, a second tankis automatically put into service at this time. Allpiping to the tank should have welded joints toassure no possibility of leakage. A concrete curbshould be provided to contain the liquid in theevent of a rupture in the system. The necessity formicrobiological monitoring of the effluent fromthe system should be considered in the designprocess, to ensure that adequate valves, samplingports, etc., are incorporated in the design for re-moving samples.For larger volumes of effluent, a continuous-

flow arrangement (Fig. 19) that utilizes injectedsteam to raise the liquid to a proper temperaturemay be used. In this case, the effluent-steam mix-ture flows through a series of retention tubes andis cooled through a heat-exchanger before beingdiscarded.

Liquid waste treatment systems can be moni-tored and controlled from a central panel whereflow arrangements, effluent volumes, treatmenttimes, and temperatures are visually indicated.

LITERATURE CITED1. CHATIGNY, M. A. 1961. Protection against infec-

tion in the microbiological laboratory: devicesand procedures. Adv. Appl. Microbiol. 3:131-192.

2. DECKER, H. M., L. M. BUCHANAN, L. B. HALL,AND G. D. GARDNER, JR. 1962. Air filtration ofmicrobial particles. Public Health ServicePublication 953, Washington, D.C.

3. DOLOWy, W. C. 1961. Medical research labora-tory of the University of Illinois. Proc. AnimalCare Panel 11:267-280.

4. GLICK, C. A., G. G. GREMILLION, AND G. A.BODMER. 1961. Practical methods and problemsof steam and chemical sterilization. Proc.Animal Care Panel 11:37-44.

5. HORSFALL, F. L., AmD J. H. BAUER. 1940. In-dividual isolation of infected animals in a singleroom. J. Bacteriol. 40:569-580.

6. KIRCHHEIMER, W. F., J. V. JEMSKI, AND G. BPHILLIPS. 1961. Cross-infection among experi-mental animals by organisms infectious forman. Proc. Animal Care Panel 11:83-92.

7. NORMAN, J. D. 1964. The bench concept inlaboratory planning. Health Lab. Sci. 1:179-184.

8. PHILLIPS, C. R. 1957. Gaseous sterilization, p.746-765. In G. F. Reddish [ed.], Antiseptics,disinfectants, fungicides and chemical andphysical sterilization. Lea and Febiger, Phila-delphia.

9. PHILLIPS, G. B. 1965. Microbiological hazards inthe laboratory. J. Chem. Ed. 42:43-48, 117-130.

10. PHILLIPS, G. B., G. C. BROADWATER, M. REIT-MAN, AND R. L. ALG. 1956. Cross infectionsamong brucella-infected guinea pigs. J. Infect.Diseases 99:56-59.

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11. PHILLIPS, G. B., AND E. HANEL, JR. 1960. Use ofultraviolet radiation in microbiological labora-tories. U.S. Government Res. Rept. 34:122.

12. PHILLIPS, G. B., J. V. JEMSKI, AND H. G. BRANT.1956. Cross-infection among animals chal-lenged with Bacillus anthracis. J. Infect.Diseases 99:222-226.

13. PHILLIPS, G. B., AND F. E. NOVAK. 1956. Applica-tions of germicidal ultraviolet in infectiousdisease laboratories. II. An ultraviolet pass-through chamber for disinfecting single sheetsof paper. Appl. Microbiol. 4:95-96.

14. PHILLIPS, G. B., M. REITMAN, C. L. MULLICAN,AND G. D. GARDNER, JR. 1957. Applicationsof germicidal ultraviolet in infectious diseaselaboratories. III. The use of ultraviolet barrierson animal cage racks. Proc. Animal CarePanel 7:235-244.

15. RUNKLE, R. S. 1964. Laboratory animal housing.Am. Inst. Architects 41:55-58, 77-80.

16. SNow, D. L. 1963. Space planning principles forbiomedical research laboratories. Public HealthMonograph 71.

17. WEDUM, A. G. 1953. Bacteriological safety. Am.J. Public Health 43:1428-1437.

18. WEDUM, A. G. 1964. Laboratory safety in re-

search with infectious aerosols. Public HealthRept. 79:619-633.

19. WEDUM, A. G., E. HANEL, JR., AND G. B. PHILLIPS.1956. Ultraviolet sterilization in microbiologicallaboratories. Public Health Rept. 71:331-336.

20. WEDUM, A. G., E. HANEL, JR., G. B. PHILLIPS,AND 0. T. MILLER. 1956. Laboratory designfor study of infectious disease. Am. J. PublicHealth 46:1102-1113.

21. WEDUM, A. G., AND G. B. PHILLIPS. 1964. Criteriafor design of a microbiological research labora-tory. ASHRAE (Am. Soc. Heating Refrig.Air-cond. Engrs.) J. 6:46-52.

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