CDC turns up the regulations: Hospitals turn to open concept labs for flexibility and efficiency

By Clarence Lind, AIA

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With the advent of the HIV epidemic and the rise of imported exotic microbes, a heightened awareness of the need for isolated testing laboratories within the general hospital laboratory has been firmly established.

More recently, growing concerns about bio-terrorism are leading to the development of comprehensive federal guidelines for isolating special testing protocols.

In the near future, it appears that the Center for Disease Control (CDC) will recommend that most hospital laboratories contain a Biosafety Level 3 (BSL-3) laboratory or an equivalent procedure.

Currently, most hospital laboratories operate at a BSL-2 level, with isolated labs within that approach a BSL-3 level. These isolated labs can be located in both the clinical and anatomic parts of the lab, but usually for very different reasons. The clinical labs need to protect the staff and environment from biological agents and the anatomic labs need to protect staff primarily from the fumes generated from the solvents used. In some cases, there is also a need to protect the specimens from outside contamination that might alter the results.

Clinical laboratories

In clinical laboratories, special testing labs for areas such as virology, mycology, hepatitis, tuberculosis and HIV testing, specimens are prepared by the staff and commonly analyzed by specialized procedures and automated instruments.

In these situations, lab technicians need to be protected from potentially infectious specimens; and there is also a need to prevent the microbes from spreading to other areas of the lab or to other staff. The specimens also must be protected from being contaminated, so that the testing can lead to an accurate diagnosis.

In newly evolving tests, such as genetic coding, the concern for contaminating specimens is especially high. Some labs are also beginning to perform DNA amplification and molecular diagnosis, and these tests require very clean, protected environments.

Specimens must be carefully handled and isolated so that the results are as accurate as possible. Even labs that are not performing any of these specialized testing protocols may need to provide some minimum level of isolation within their labs to test specimens of patients with suspicious symptoms of unknown origin.

These isolated labs require a negative air pressure relative to other adjacent areas that prevents any contaminated air from going outside of the lab. The current practice is to also handle these hazardous specimens in biological safety cabinets (BSC) designed to protect the staff, the specimens or both and come in Classes I, II or III.

Class I and II BSCs have open fronts and provide good protection for the staff. Class II and III BSCs also have the capability to protect the specimens. Class I and II BSCs are normally used in BSL-2 and BSL-3 labs and Class II and III BSCs are normally used in BSL-3 and BSL-4 labs. All the BSCs supply or exhaust air through HEPA filters and may use other protective devices such as ultraviolet lighting and glove ports.

A BSL-3 laboratory should not be confused with a cleanroom because they are operationally different. Cleanrooms used for the fabrication of microchips and manufacturing of pharmaceuticals, for example, are far more concerned about protecting the space with the lab from outside contaminates, whereas a BSL-3 lab's purpose is to contain the materials within the lab to prevent them from contaminating areas outside of the lab.

However, with the development of new BSL-3 recommendations, hospital labs will have more stringent training and operational requirements for technicians.

For example, an anteroom (air-lock) may be needed for staff to change into protective garments before entering the lab and to also house pass-thru autoclaves to decontaminate any specimens or other potentially contaminated materials before being removed from the lab. Security will become far more important to prevent unauthorized persons from accessing dangerous biological agents and removing them from the lab.

Currently, the typical isolated lab is finished with floors, walls and ceilings that are easily cleaned and don't absorb contaminates or moisture. Standard floor tiles cannot be used because of the tile joints, so both floors and walls are usually finished with highly durable epoxy coatings.

Ceilings are normally built with gypsum wallboard and are also finished with an epoxy coating. In some cases, a mylar-coated acoustic tile ceiling system may be used, depending on the activities occurring in that particular lab. Metal casework is usually used instead of wood because it doesn't absorb fluids and is more easily cleaned.

Counter tops cannot be made of the usual plastic laminate, which can separate from its substrate and absorb fluids. In this case, epoxy tops are commonly used, but it's not unusual to also use stainless-steel countertops.

Lighting fixtures must be easily cleaned and ultraviolet lights are sometimes used to kill airborne germs. Some isolated labs include warning signs or lights outside the entry to the lab to warn people if there is testing under way or if there has been a spill or other accident.

Security is also important with door locks being the most common method used. Other security measures may include surveillance cameras, where needed.

Anatomic laboratories

Anatomic labs generally handle the testing of tissue specimens and organ biopsies. The most common problem in anatomic labs is with the fumes generated by the fixing agents and solvents used in preparing and storing specimens. Solvents such as xylene can produce strong fumes that can be harmful to the staff and can, at times, require extraordinary ventilation methods that may exceed the air changes normally used to ventilate a surgery room.

Innovations in tissue processing instrumentation have greatly improved the situation. In the past, solvent vials were commonly left uncovered, allowing the free evaporation of solvents into the room air. The new tissue processors are self-contained, with charcoal filtering to capture the fumes and clean the exhausted air.

Solvent manufacturers are also trying to create new solutions that are not based on xylene or formaldehyde. Some of these new solvents are being used now, but they are receiving mixed reviews regarding their acceptability. In the meantime, most labs are still dealing with the traditional fume-producing solvents. In addition, they are also required to collect the solvents, which cannot be discarded or dumped down drains.

Some labs pour the solutions into storage containers that are then collected by an outside contractor. Other labs have invested in solvent stills that are used to distill the solutions and remove impurities so they can be reused. These labs must make space for the distillation equipment and processing.

Fumes are also generated during the staining of cut tissues when preparing slides for microscopes studies. Technicians usually work with these slides under small portable containment hoods with self-contained charcoal filters. For this approach to be successful, however, the filters must be recharged on a regular basis. One of the downfalls of using these hoods is that many technicians do not realize that the charcoal filters have become saturated and are no longer effective, thus giving them a false sense of security.

The best solution to this problem is to exhaust the fumes directly away from the work area as quickly as possible, not allowing them to infiltrate into the room. Linear exhaust grills in the wall immediately above the work surface can be placed behind the countertops where the staining and coverslipping work is done.

Being closer to the work reduces the velocity needed to capture the fumes before they can flow off the countertop. Conventional ceiling exhaust grilles are too far from the work surface and cannot generate the velocity needed to remove the fumes, which are heavier than air and resist efforts to exhaust upward.

Stepping up to BSL-3

So what must the hospital do to create a BSL-3 laboratory? The CDC has classified laboratories into four categories depending on how hazardous the materials are. The categories vary from a BSL-1 through BSL-4).

A BSL-1 laboratory has the lowest level of containment with biological agents posing minimal hazard to laboratory staff or the general workspace environment. On the other hand, a BSL-4 lab has the highest level of containment, with biological agents posing a high risk to staff health and safety that could be life threatening.

A BSL-3 lab—while not dealing with microbes as hazardous as a BSL-4—also works with potentially dangerous specimens or materials that may cause serious or lethal diseases to staff exposed to them.

Most general clinical areas of the hospital laboratory function at a BSL-2 level. An excellent source for more information on these biological safety levels is the CDC/NIH guideline, Biological Safety in Microbiological and Biomedical Laboratories.

In general, each biosafety level builds upon and creates a more contained environment than the previous level. However, it is usually difficult to remodel an existing BSL-2 lab into a BSL-3 lab because of the requirements for limiting access, anterooms, HVAC decontamination processes and other special physical criteria.

Therefore, new laboratories should strongly consider including a BSL-3-equivalent space in their program and design using the appropriate criteria. The finished space can be used for general laboratory work, but could be readily converted into a BSL-3 lab if or when conditions warrant.

Because of the difficulty and high cost of converting a BSL-2 lab into a BSL-3 lab, the guidelines indicate that it may be possible to use an existing BSL-2 lab providing the hospital can meet the safeguards recommended for BSL-3 level laboratories. Each situation would need to be evaluated individually to determine whether acceptable safeguards can be met and maintained. In the meantime, we will all need to wait and see what the final recommendations will be. A recent article titled “Laboratory Security and Emergency Response Guidance for Laboratories Working with Select Agents”1 provides a glimpse of what the future holds.

Clarence Lind, AIA, HDR, has designed 35 hospital labs with HDR. He can be reached at [email protected].


1. “Laboratory Security and Emergency Response Guidance for Laboratories Working with Select Agents,” Dec. 6, 2002/Vol. 51/No. RR-19, Epidemiology Program Office, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services.


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