[This tape was duplicated from 16mm original by Colorlab for the National Library of Medicine, July 2004, NLM call number HF 1079]

[The U.S. Department of Health, Education, and Welfare Public Health Service Presents] 

[Laboratory Design for Microbiological Safety] 

[Produced for National Institutes of Health, National Cancer Institute, Special Virus Leukemia Program]

[In Cooperation with The Ohio State University Department of Veterinary Pathology, The National Drug Company 

Biological Research Laboratories, The Brooks Air Force Base School of Aerospace Medicine, The Naval Biological Laboratory,

The U.S. Army Biological Laboratories, The Public Health Service Taft Sanitary Engineering Center, 

The U.S. Department of Agriculture National Animal Disease Laboratory, The Virus Laboratories California Dept. of Public Health,

The Medical Research Laboratory , University of Illinois 

[A Public Health Service Audiovisual Facility Production] 

[Dr. A.G. Wedum:] Every year approximately 175 million dollars are spent on constructing and remodeling biomedical research facilities 

in the United States. 

Of this amount, a significant portion is directed to laboratories handling infectious microorganisms. 

Because of the magnitude of this investment and the hazards to laboratory personnel, it is important that microbiological safety measures 

be incorporated in the design of infectious disease laboratories. 

These measures are needed to prevent accidental occupational infections among laboratory workers, to safeguard the health 

of the surrounding community, and to prevent false laboratory results due to cross-infection of animals or cultures. 

The purpose of this film is to describe and illustrate some of the principle building features and devices 

used to provide effective microbial containment.  

In determining what safety measures to incorporate in the design of infectious disease laboratories, 

much research and study was necessary. 

For instance, we needed to understand how laboratory workers become infected and how microorganisms might escape and spread 

within the building or escape to the surrounding community. 

During the study it was found that infectious agents are let loose into a laboratory worker's environment 

in a manner and in quantities that  cannot always be detected. 

However, these infectious agents can be contained by establishing a system of enclosures or barriers within the building. 

Thus, from research and study the concept of primary and secondary barriers evolved. 

The enclosures immediately surrounding infectious agents are the primary barriers. 

The most important are the ventilated safety cabinets. 

Other primary barriers include such items as closed, ventilated animal cages, safety centrifuge cups, and safety blendor bowls. 

All serve as the first line of defense against the escape and possible spread of infectious microorganisms. 

The secondary barriers in a laboratory are the features of the building that surround the primary barriers. 

These provide a separation between infectious areas in the building and the outside community, 

and between individual infectious areas within the same building. 

Such features as walls, floors, and ceilings, ultraviolet airlocks and door barriers, 

and properly arranged personnel change rooms and showers are considered secondary barriers. 

Increasingly negative air pressure as one moves from a clean area to one of greater infectious risk 

can also be classified as a secondary barrier. 

Furthermore, the equipment for filtering air exhausted from laboratory rooms comes under this classification, 

as well as the facilities for treatment of potentially contaminated liquid waste. 

These and other secondary barriers generally are thought of as providing supplementary biological containment, 

serving mainly to prevent the escape of infectious agents if and when a failure occurs in the primary barriers. 

Actually, the more effective the primary barriers are, the less need there is for emphasis on secondary barriers. 

Therefore, during the design phase of any infectious disease laboratory, it is both important and economically necessary 

to first determine and select the primary containment devices to be used. 

[Narrator:] Early in the design of any new infectious disease building, definitions should be made of the five functional zones 

and their relationship to each other. 

There can be numerous physical arrangements of these zones. 

However, in this film we will consider one standardized floor plan as being typical, 

and showing most of the recommended containment features. 

The first functional zone we shall consider is the clean area. 

Here are located the main entrance to the building, offices, conference rooms, and library where administrative work, meetings, 

and similar activities are carried on. 

Also within this area are transitional rooms through which lab personnel enter and exit from the infectious areas of the facility. 

These consist of a clean change room equipped with toilets, storage space for laboratory clothing, and lockers. 

A non-ventilated airlock with UV lights, a shower room, and a contaminated change room equipped with toilets, 

storage racks for shoes, and a UV-shielded bag for discard clothing. 

In the rear of the facility is also a clean area with a transitional airlock. 

This serves to handle the inward flow of laboratory supplies into the building and the outward flow of materials from the building. 

Supplies entering the infectious areas are passed in through the UV airlock. 

Potentially infectious material leaving the building is treated in a double-doored steam or ethylene oxide sterilizer. 

Let's now observe some of the design features that one might see in the clean zone. 

Personnel usually enter the facility into a clean area in the front of the building, including the offices and other support areas 

pertinent to the operation of a laboratory. 

Clean offices, when located adjacent to the contaminated zone, make possible easy visual communication 

through a large viewing window and minimize personnel traffic between the two zones. 

Oral communication between the clean and infectious areas of some laboratories is often provided by means of speaking diaphragms. 

A tightly sealed plastic membrane provides the medium through which the sound passes. 

Treatment of data sheets and other papers sent from the contaminated to the clean zones is accomplished 

by passing them through an ultraviolet apparatus. 

Lever-driven rollers push the paper through at a constant rate. 

This assures adequate decontamination of each sheet. 

For treatment of envelopes, folders, and books, equipment pass-in locks utilizing cold sterilization  

with ethylene oxide are recommended. 

This through-the-wall, double door chamber allows sterilization of items in about twelve hours, 

after which the items can be removed in the clean zone. 

The passage of personnel from clean to infectious zones should be through a clean change room. 

After changing into lab clothing, they pass through a non-ventilated ultraviolet airlock and then on into a contaminated change room. 

Personnel leaving infectious zones go through the same change rooms but in reverse order. 

After returning their shoes to the storage racks, their lab clothing is discarded into a bag screened with UV. 

They then take a shower using a germicidal soap. 

Finally, they return to the clean change room, passing first through the airlock. 

In the clean area at the back of the building there is another transitional airlock. 

Here supplies and equipment needed for lab operation are delivered. 

Once the outer door is closed, an electrical interlock allows personnel in the contaminated area access to the airlock to remove supplies. 

Returning to our floor plan, let's look at the second functional zone of a typical facility, the lab research area. 

Here, infectious microbiological operations exclusive of animal work are performed. 

Located in this area are the potentially infectious lab offices. 

The individual laboratory rooms are usually equipped with one partial barrier safety cabinet 

for work of low to medium risk and a free-standing, single-door autoclave. 

At least one room should contain a gas-tight, absolute barrier cabinet system for performing high hazard operations with a minimum hazard. 

The system should terminate in either a double-doored autoclave or a germicidal liquid bath. 

Other common features usually found in this research area are an instrument room for centrifuges and other apparatus, 

and constant temperature rooms for incubation and refrigeration. 

The hallway, with air pressure positive to the lab rooms, provides additional room-to-room separation. 

Let's examine some containment features found in this area, remembering that this is where the bulk of research and diagnostic work is done. 

The laboratory zone should be maintained at an air pressure negative to the clean zone. 

The lab rooms themselves should have an air pressure negative to the adjoining halls.

And the ventilated cabinets should be negative to the rooms. 

Ultraviolet fixtures in the ceiling that are turned on when the room is vacant will aid in reducing nonspecific microbial flora. 

A special switch in the corridor indicates when the light is on. 

For accidents involving chemicals or fire, emergency showers may be installed convenient to the research area. 

Particular attention should be given to the selection of building materials and methods of construction. 

Due to the need for periodic decontamination, paints and coatings used on walls and other surfaces must be resistant to steam, 

disinfectants, and frequent washings. 

Walls, wall curbing, and ceilings should be free of cracks. 

Often a monolithic covering is used on the floors. 

In order to facilitate cleaning operations and to prevent leakage of organisms from the lab area, casework should be sealed to the wall. 

Equipment not sealed to the wall, such as cabinets, tables, and chairs, may be mounted on wheels 

to facilitate decontamination and cleaning. 

Lighting units and other features that penetrate the barrier walls must be designed so as to assure adequate physical separation 

between the contaminated and clean zones. 

Fluorescent fixtures may be ceiling-mounted and serviced from within the room, or they may be installed above the ceiling 

encased in glass and serviced from a clean attic. 

A good gasket and seal is necessary to prevent the spread of contamination from the room into the attic. 

Where frequent wash-downs of the area are necessary, watertight units such as these should be employed. 

Also the electrical outlets in the room should be watertight to prevent water damage, 

and internally sealed to prevent leakage of contamination. 

To provide safe working conditions for maintenance personnel, electrical panels and utility spaces 

should be located in the clean area. 

Services penetrating the wall should be sealed airtight at the wall to preserve the secondary barrier. 

Particular attention should be given the safety features of walk-in refrigerators and incubators. 

Door should be equipped with viewing windows and speaking diaphragms 

so that personnel may observe operations before entering. 

Control switches for electrical outlets are usually located outside. 

The most important containment feature of the infectious disease laboratory is the ventilated safety cabinet. 

This primary barrier device isolates the laboratory worker's most potentially infectious environment. 

Although there are many different cabinet designs, there are only two basic types: 

the absolute barrier, represented by a gas-type modular system, and the partial barrier with its open panel. 

Both need to be resistant to a variety of physical and chemical materials and therefore are best constructed of stainless steel. 

Let's consider the partial barrier cabinet in detail. 

Here is an open-front type commonly used for low hazard manipulations. 

For slightly higher risk levels, glove panels without the gloves may be attached to the cabinet 

to increase the rate of air flow and reduce spilling and spattering of materials from the cabinet. 

The cabinet uses a high-efficiency microbial filter for air leaving the unit. 

The air is ducted to the nearest exhaust manifold. 

Some partial-barrier cabinets are equipped with front panels with attached arm-length rubber gloves 

to provide a greater degree of microbial control. 

With this cabinet there is a saving in operating cost, since it requires very little conditioned air 

as compared to that needed for the open-faced type. 

Steam is one of the desired services and is used with formaldehyde to decontaminate both the inside of the cabinet 

and its exhaust air filter. 

The other basic type of safety cabinet is the absolute barrier unit. 

It provides a total separation between the infectious working areas and the surrounding laboratory. 

This cabinet system can serve as a complete contained laboratory for the most hazardous microbiological procedures. 

It is modular in construction and the individual units may be fitted together in any desired configuration and length. 

These gas-type cabinet systems can vary widely in arrangement. 

Maximum utilization of floor area can be achieved by double stacking the cabinets and placing them around the walls. 

Others might be straight-line units that extend through a wall. 

This particular design speeds up workflow between two separate rooms. 

The possible internal features for absolute barrier systems are almost limitless. 

They include interconnecting gas-tight doors, back-mounted incubators, 

bottom-mounted, Lazy Susan refrigerators, 

bottom-mounted centrifuges, and other devices. 

The third functional zone in a standard facility is the research area for both small and large infected animals. 

This usually includes laboratories having appropriately ventilated cabinets for inoculation and autopsy, 

and animal rooms equipped with such isolation equipment as ventilated cages and UV cage racks. 

In some instances it may be desirable to locate,in a room adjoining the animal room, aerosol exposure equipment, 

such as the Henderson apparatus. 

Also, if not available elsewhere, the animal area should have an incinerator for disposing of animal carcasses 

and a large autoclave for sterilizing cages and passing them into a cage-washing room. 

In designing this research area, the type and degree of animal isolation should be considered early. 

It should always provide for safe working conditions for lab personnel and prevent undesired animal cross-infection. 

In rooms housing small infected animals the hazard level is sometimes high enough to require that protective clothing 

and respirators be worn by laboratory personnel. 

In the animal rooms, dust filters should be installed in the air exhaust ducts to prevent excessive loading 

of the downstream microbial filters with animal hair and dander. 

The recommended ventilation rate for the rooms is fifteen changes per hour of non-recirculated, draft-free air 

of the relative humidity and temperature appropriate to the animal species. 

Since the walls and floors of both large and small animal areas are washed frequently and exposed to urine 

and other wastes, careful selection should be made of wall paints and finishes. 

The nature of some disease agents in small animals is such that no special provisions are needed 

to prevent animal cross-infection or to protect animal handlers. 

However, there are some infectious agents that require animal isolation equipment for protecting personnel. 

One design is a ventilated cage rack compartment, similar to a fume hood. 

This unit has sliding doors, an inward flow of air, and filtration of exhaust air. 

By a design modification utilizing a bolted-on plastic panel, this compartment becomes a gas-tight, absolute barrier unit. 

It is maintained at a negative pressure and is supplied with filtered air. 

The exhaust air is also filtered. 

Here work with animals is done through attached rubber gloves. 

Infected animals in this system can be handled and then passed on to an adjoining cabinet for autopsy or another investigative procedure. 

In other situations where a high degree of isolation is required and where animal-to-animal separation is needed, 

infected animals are held in small, individually ventilated cages. 

In some instances instead of closed ventilated cages, animals may be housed in cages under an ultraviolet barrier. 

Non-portable, ventilated animal compartments have been found effective in some infectious disease laboratories. 

Each of these Horsfall units holds one or two animal cages and is equipped with a viewing window and inlet and outlet air filters. 

This particular version utilizes pads of spun glass for air inlet filters. 

The exhaust air, after filtration, goes to a common exhaust manifold. 

Cages of this type must be decontaminated in place. 

A pressurized, ventilated suit provides another form of personnel protection during the housing and handling of infected animals. 

Following its use, the attendant must decontaminate the outside 

with a solution of two percent peracetic acid or another liquid decontaminant. 

It is convenient to locate small animal holding rooms close to rooms where inoculation and autopsy are done. 

With disease agents of low hazard, tabletop autopsy is permitted. 

In this case the operator should wear a respirator. 

For higher hazard work, animal autopsy should be done in ventilated safety cabinets 

where an inward sweep of air prevents the accidental escape of infectious aerosol. 

Where maximum protection is required, an absolute barrier cabinet system with attached rubber gloves must be used. 

This cabinet is equipped with an autoclave for sterilizing animal carcasses and other materials removed from the system. 

Large animals usually are housed and studied in facilities separate from those for small animals. 

In this suite the animals are infected with epizootic diseases not transmissible to man. 

Here are located a series of adjacent rooms and stalls for housing, inoculation, surgery, autopsy, and incineration of carcasses. 

Laboratory personnel entering the area should pass through a change room and dress in proper clothing. 

Necessary supplies, such as food and equipment, should be brought in through properly designed airlocks, 

and stored temporarily in adjacent storage rooms and feed vestibules. 

In the design of holding rooms, attention should be given to their flexibility so as to accommodate 

various sizes and species of animals. 

This may be accomplished by using a room equipped with removal stanchions and partitions. 

The room should be constructed to withstand frequent washing and cleaning. 

Furthermore, it should be provided with vestibules for storage of feed. 

Not only must the individual rooms be cleaned, but the corridors serving them must be hosed down frequently. 

In some large animal research areas it is desirable to have a hydraulically operated tilt table for surgery. 

Occasionally animal monitoring equipment also is provided. 

After an autopsy, provisions should be made for transporting the carcass. 

Here a large pan, supported from a monorail is used to carry the carcass through an airlock to the incinerator. 

When the incinerator is part of the infectious area, the firebox should be maintained at negative air pressure to the room, 

in order to prevent blowback of contaminated materials. 

The fourth zone in a lab facility is designated as laboratory support. 

This is best located outside the contaminated research areas, 

and includes rooms for washing and sterilizing glassware and animal cages, 

preparing culture media, storing glassware and animal cages, and repairing various laboratory items. 

A more detailed look suggests that due to the many heat-generating devices and odor-producing procedures 

in this area, careful attention should be given to the design of a ventilation system. 

Also, because of the great amount of water involved in washing operations, 

doors, walls, and other surfaces should be resistant to moisture. 

In glass washing, non-contaminated glassware may be processed either in a tunnel-type machine that allows for an automatic 

continuous flow of items, or a batch-type washing unit for small amounts. 

The sterilization equipment needed in lab support consists principally of dry heat ovens and steam sterilizers. 

In the cage-washing room, small animal cages may be processed in a continuous flow tunnel-type machine. 

Where larger units are processed, a batch-type washer with multiple or rotating spray heads often is used. 

When the cage debris contains highly infectious organisms, the cage with its debris should always be sterilized 

before it enters the lab support area. 

Another lab support activity is the preparation of culture media. 

The room for this should have a controlled movement of filtered supply air during the 

pouring of the plates and the preparation of other sterile media. 

To limit the ingress of microorganisms, air in the room always should be maintained 

at positive pressure to the other lab support rooms. 

An adequate storage room should be provided for glassware, animal cages, and other equipment, 

as well as a small machine and glass repair shop. 

The fifth functional zone in the lab facility provides engineering support. 

Included here are the necessary pipes, ducts, pumps, blowers, and filters, as well as the liquid waste treatment system, 

and the bulk of the air-handling system. 

Special engineering arrangements should maintain the integrity of the secondary barrier when penetration of the wall is made by pipes, 

wires, and ducts regardless of whether the engineering zone is located on the same or a different level from the other functional zones. 

As much of the engineering support area as possible should be located outside the contaminated zone, 

possibly on the grounds adjacent to the building, or in the basement, or attic of the facility. 

Because of the large amount of engineering equipment needed, more than half of total building area is sometimes required. 

The most important engineering functions are air handling and ventilation, often involving nearly 50 percent

of the cost of the laboratory building. 

One vital consideration is the need to locate the air intake grill upwind to the exhaust stack. 

There should be adequate physical separation between both to prevent cross-contamination. 

In engineering support, air ducts going to each room in the infectious zone should deliver nonrecirculating, filtered, and conditioned air. 

In virus labs, inlet air is often passed through ultra high efficiency filters. 

These ducts need not be of airtight construction. 

Exhaust air ducts coming from the infectious zone must be airtight, however, to assure no leakage 

infectious microorganisms before air reaches the exhaust filter plenum. 

Galvanized ducts with taped, epoxy-coated joints have been found satisfactory. 

The exhaust air plenums in the building are often designed to serve several laboratory rooms of about the same hazard level. 

They may be equipped either with high efficiency spun glass mats or with ultra high efficiency units 

for filtering air discharged from the rooms. 

Since the filters in the plenum must be changed periodically, provisions must be made 

for decontaminating both the filters and the plenum itself before opening the unit. 

A mixture of steam and formaldehyde is used as the decontaminating material. 

The facility's ventilation system should provide an interlock between the exhaust and supply blowers. 

This is to prevent pressurization of the infectious zones in case the exhaust blower fails. 

A pneumatic control system senses the air pressure in each room and assures correct air balance throughout the laboratory. 

Exhaust air from aerosol chambers and other high-hazard equipment should pass through welded pipelines to an incinerator. 

Electrically operated units are both practical and efficient for quantities of up to 100 cubic feet a minute. 

This unit and the ones that follow should be preceded by a microbial filter as a failsafe device. 

For larger volumes of air, gas or oil-fired incinerators may be used. 

With this oil-fired unit a tall stack serves to discharge the air at a substantial distance above the building. 

An important part of an engineering support zone is the central control board. 

Here readouts of all systems in the area can be readily monitored by engineering personnel. 

Such boards should have visual and audible alarms that will automatically signal the failure of any part of the system. 

Another important item is the standby electrical generator. 

It is used in the event commercial power supply is interrupted. 

Sometimes the units are mounted in trailers to provide easy portability. 

In some laboratories facilities must be provided for treating contaminated liquid waste. 

Two basic systems are employed, the batch and the continuous flow. 

The batch system, shown here, is used to collect waste from infected animal areas. 

Liquids flow by gravity to the tank where they are sterilized by adding steam and holding for a period of time. 

The piping should have welded joints to assure no possibility of leakage. 

Note that a concrete curb has been provided to contain the liquid in the event of a rupture in the system. 

Where larger volumes of waste are produced multiple batch treatment tanks are used. 

Here is a continuous flow arrangement which utilizes steam to raise the liquid to a proper temperature. 

The waste flows through a series of retention tubes and is cooled through a heat exchanger before being discharged. 

All such systems can be monitored and controlled from a central board where floor arrangements, 

waste volumes, treatment times and temperatures are visually indicated. 

[Dr. A.G. Wedum:] This film has emphasized the concepts of the primary barrier and the secondary barrier 

in designing a laboratory for the study of infectious disease. 

These concepts apply to the five functional zones, namely: 

the clean, the laboratory research, the animal research, the laboratory support, and the engineering zones. 

The film has given examples of how various operating laboratories have used these concepts. 

Although there is no complete substitute for careful training and good microbiological technique 

by a knowledgeable laboratory supervisor, sooner or later a point may be reached in the experimentation 

when there's need for a building and equipment with emphasis upon protection for the investigator, 

the experiment, and the public. 

The film has served its purpose if it provides significant assistance to those persons responsible 

for the design, construction, and operation of laboratories for the study of infectious disease.

[The End  M-1091] 

[Director Durward R. Thayer, Technical Advisors A.G. Wedum, M.D. G Briggs, Ph.D.]