Safe containment lab design follows clear protocols
04/01/2005
A BSL-3 lab and Animal BSL-3 lab can be simple or sophisticated, depending upon their purpose. Regardless, successful design must take into consideration material flow, people flow and waste flow.
Charles Warren, P.E., HDR Architecture
Sean Towne, AIA, Research Facilities Design
Biosafety Level 3 (BSL-3) containment laboratories allow researchers to handle exotic or indigenous agents that can cause lethal infection by inhalation. Therefore, these laboratories must be planned carefully. A successful BSL-3 lab is designed with protocol in mind: How are researchers within the lab going to operate to prevent live microorganisms from infecting personnel or escaping the facility? That protocol includes defined practices and procedures for material flow, personnel flow and waste flow.
Material flow
In managing samples and materials, there are many issues to consider related to material flow and researcher safety. Primary to managing sample materials is the utilization of directional airflow and filtration. Class II Biological Safety Cabinets (BSCs) are designed into containment labs as the primary barrier protecting the researcher as well as the samples. The type of BSC is an important decision and will determine whether the BSC should recirculate filtered air back into the lab or exhaust the air fully outside the building. A recirculated BSC has built-in filters that capture biologicals or microbe-level particles. If materials that generate hazardous or toxic fumes are used, the system will need to be exhausted out of the building, as these fumes would not be captured in the biological filters.
 Figure 1. A BSL-3 laboratory at Johns Hopkins University School of Medicine, Bunting-Blausteing Cancer Research Building, in Baltimore, Maryland. |
Maintaining negative air pressure from areas of higher to lower risk and closely monitoring and alarming this pressure also are fundamental to effective containment lab design. These pressure differentials must be alarmed to make sure people are notified if something is not working properly.
For example, in a recent BSL-3 project, the containment lab suite was maintained at a negative pressure relative to the adjacent corridors. Additionally, the five independent workrooms within were designed to maintain a negative pressure relative to the rest of the BSL-3 suite. The differential pressures between the suite itself and the adjacent areas were monitored, as was the differential pressure between the workrooms and the remainder of the suite. The pressures were displayed in a panel on the wall outside the door to each workroom and outside the BSL-3 lab. If the differential pressure were to fall below the set point, a local visual and audio alarm would signal. A remote alarm also would be sent to the building energy-management system so personnel would know there was a potential containment failure.
When live subjects are required for level-3 research, animal-containment facilities must be developed. As a complement to the BSL-3 suite referenced above, an ABSL-3 suite was designed into the facility’s large vivarium. While the overall ABSL-3 suite maintained negative pressure to the rest of the vivarium, each animal holding room was designed at a negative pressure to the vestibule to protect the animals from outside contamination. Also, the vivarium was supplied with 99.99 percent HEPA-filtered air. The mice that are housed in the animal holding rooms are kept in cage racks, which have their own HEPA-filtered supply air system, with its air source being the HEPA-filtered room air.
 Figure 2. One of five BSL-3 labs at the University of Virginia, Biomedical Engineering and Medical Sciences Building, in Charlottesville, Virginia. |
Another issue that this project addressed was disinfection of the laboratory vacuum lines serving the BSL-3 lab. Specifically, laboratory vacuum was piped to each of five research workrooms to help with the experiments, and a disinfectant trap was placed on the lines leaving the area.
Finally, discussing and understanding the sequence of events, the failsafe conditions of the mechanical systems and the exhausted safety cabinets is a critical systems-engineering issue. Containment of contaminants is based largely on air movement or pressurization from air movement. If the power to the building fails, the mechanical system for the facility must be independent and supplied by emergency power. But there is often a time lag between the power failure and when the emergency power kicks in-roughly 20 to 30 seconds-so discussing and understanding emergency conditions is very important.
Personnel flow
Depending on the lab’s purpose and protocol, movement of research, maintenance and decontamination personnel into and out of a BSL-3 can be complicated and requires significant floor area allocation. These personnel movements bring about several considerations.
The entrance sequence to a BSL-3 containment facility must provide at a minimum an area for gowning up in a vestibule with interlocked doors. Sophisticated level-3 facilities allow for both male and female locker rooms, which may include pass-through clothes lockers. The protocol for personnel exiting a level-3 facility can include a directional path through a degowning vestibule, a water shower and a locker dressing room before exiting into a corridor. The interface between exiting personnel and decontamination of garment and disposables sometimes is accomplished with a pass-through between the degowning vestibule and the dirty side of a pass-through autoclave room.
The requirement of moving personnel in and out through the entry and exit sequences can take up significant space. It is not unusual for half of the definable space in a BSL-3 or ABSL-3 facility to be allocated to these functions and circulation.
Another consideration related to personnel flow is the placement of the mechanical equipment that serves a containment facility. In both the BSL-3 and ABSL-3 suites in the previously referenced project, the mechanical equipment was placed above a hard-lid, structural ceiling with walk-on capacity for maintenance access from outside the containment labs. Whenever the equipment needs to be serviced, maintenance people can reach it without going through the BSL-3 lab or the critical areas of the vivarium.
Situating this BSL-3 suite on the top floor of an eight-story facility also allows for its independent mechanical exhaust system to serve the containment lab directly without eating up vertical shaft space on other floors.
Waste flow
Similar to personnel flow, decontaminating waste, instruments and other materials can take up a lot of floor space, and this requires a clear understanding of the preferred operating protocol. Eliminating clean/dirty crossovers is critical in contamination control. Here, there are several things to consider.
Effluent treatment and disposal can be an inexpensive manual process or a very costly comprehensive automated system. If the lab is small and contains only hand-washing sinks, disposing of the waste water can be as simple as holding it in the sink until it is decontaminated with bleach or another material and released into the system. For a large containment lab, which may include sinks, instrument waste lines, showers and even a restroom facility, effluent might be collected below the floor level in a kill tank-in effect, a large autoclave-where the waste water from the entire lab is captured and sterilized before being released into the sanitary system.
Pass-through autoclaves are common pieces of equipment for BSL-3 facilities, although in some cases very small
Whether simple or sophisticated, designing a BSL-3 or ABSL-3 laboratory relies on clearly defined protocols for material, personnel and waste flow. A successfully designed containment lab provides researchers, maintenance personnel and building operators with efficient, manageable facilities that protect each from the very real dangers of Biosafety Level 3 work. III
Charles “Chip” Warren, P.E., is lead mechanical designer/engineer with Omaha, Neb.-based HDR Architecture. He can be reached at [email protected].
Sean Towne, AIA, served as a lab consultant and is with San Diego-based Research Facilities Design (RFD). He can be reached at [email protected].