Ebola, hemorrhagic fever, the Nipah virus—come in contact with any one of these and your chances of death are almost certain. Yet scientists and researchers come into close proximity to these pathogens all the time without being harmed. How is that possible? The answer is in the environment in which they work. Biosafety Level 4 laboratories are rigorously controlled environments that can take years to plan, design, and construct.
There are four designations of Biosafety Level (BSL) laboratories, increasing in protective measures as the organisms studied pose a greater risk to human health. A level 1 designation requires minimal protective equipment and handwashing, while level 4 requires full breathing air suits, specialized laboratory equipment, air-tight doors, and a mechanical system ensuring inward airflow into the BSL laboratory at all times.
Ensuring inward airflow across the containment boundary is a core tenet of any BSL-3 or BSL-4 design—not only for the safety of the researchers, but also for the safety of the surrounding community. To achieve this, the mechanical system and control system (building automation system) need to respond properly to environmental changes in the built environment, equipment failures, and outside influences. This highly complex interaction between the air handling units, exhaust systems, and terminal equipment requires a sophisticated approach to controlling these systems.
The level of complexity and sophistication is driven by three main factors:
- Each lab operates differently, requiring highly flexible and adaptable systems. Every BSL-3 and -4 laboratory operates differently. Each engineering system has different response times, the equipment reacts differently depending on manufacturer, and the architectural fit and finish performs differently in every facility. These subtle differences profoundly affect the control system functionality and necessitate highly flexible and adaptable systems.
- Appropriate, split-second response time is critical. Every component within the system must react quickly and in concert to avoid a reversal of airflow. Correct instrumentation and the proper motive force to drive system components like air valve actuators and dampers are critical design aspects and contribute the most to an appropriate response time of the system.
- Equipment interaction and response must be reliable and repeatable. Interlocking system components through either hardwiring or software provides the reliability needed in a BSL laboratory. Hardwiring safety devices can provide instantaneous response to a failure, however implementing hardwire interlocks in every scenario can create a very complex system that is nearly impossible to troubleshoot and maintain. Conversely, software interlocks can reduce the complexity; however, they can introduce latency into the reaction time. A proper design will strike a balance between these two strategies to arrive at a safe and reliable laboratory environment.
Complexity is inherent in the design of any BSL-3 or BSL-4 lab. Special attention is given to every facet of the design to assure that scientists and researchers can safely continue to make important advances in our understanding of these highly transmittable and often deadly threats to our local communities and society at large.
Dave Kurten, PE, LEED AP, is Building Engineering Services East Region Director—North America with HDR.