Multi-layered structural design ensures safety for high-containment labs
By David Chlebus
| High-containment laboratories, or HCLs, house potentially harmful microbes and require various levels of safety precautions, or biosafety levels (BSLs), to protect people working in the lab and the greater community. Biosafety levels range from BSL-1 to BSL-4, with BSL-4 designed to contain the highest risk microbes. HCLs most often contain BSL-3 and BSL-4 laboratories that require specific safety equipment and facility design (i.e., ensuring exhaust air from labs is not recirculated). |
Planning the design and operation of a high-containment laboratory (HCL) for researchers working with dangerous infectious pathogens requires unique, multi-layered structural design considerations to ensure the safety of building occupants and the public on a day-to-day basis and to avoid a breech in the event of a natural disaster, such as an earthquake, hurricane, or tornado.
In day-to-day operations, the ability to decontaminate is essential. To create a smooth, airtight surface for decontamination of lab spaces, the walls are typically painted with an epoxy coating that rounds over corners and creates a wipeable surface. However, this epoxy coating is brittle and sensitive to cracking in the substrate. If the epoxy cracks, it cannot be adequately decontaminated.
To avoid this issue in HCLs, the walls are commonly of cast-in-place construction. The concrete walls must not crack after the coating is applied. Much of the cracking can be mitigated with special low-shrinkage concrete mixes in combination with form liners and water curing procedures. Concrete construction must also be slowed to allow for full curing of the concrete. Patching and grinding may be required as a last measure. A trade-off is created between the amount of time allowed for concrete cure and shrinkage versus the time required to repair the wall for any cracking that does occur.
| Under the joint direction of the U.S. Department of Homeland Security and the U.S. Department of Agriculture, the National Bio- and Agro-Defense Facility (NBAF) represents the pinnacle of research for protecting food and animal agriculture supply.
The 574,000-sf facility includes BSL-2, 3, and 4 labs with new and expanded research capabilities, specifically, large animal biosafety level 4 containment for studying high-consequence diseases affecting large livestock. IMEG provided structural and security design for the NBAF, designing it to withstand a Category EF5 tornado as well as vehicular and debris impact and progressive collapse—allowing the building to stand even if some of the structural members are compromised or destroyed. Learn more about IMEG’s design here. |
Many facilities, like the Department of Homeland Security’s National Bio- and Agro-Defense Facility (NBAF), may need a second layer of containment to withstand catastrophic events. For extreme loading events, such as earthquakes, tornados, or blast loading, protecting interior walls from cracking may not be feasible. Instead, the performance requirement shifts from the operational containment within individual lab rooms to a global envelope that keeps all pathogens within the facility.
The exterior containment envelope must not only be strong enough to withstand the ultimate loading, but it also needs to be flexible and ductile enough to deform without cracking to maintain an airtight condition. To achieve this strength and flexibility a myriad of atypical structural solutions may be required. Where possible, the design may separate the structural integrity envelope from the containment envelope, allowing the former to protect the latter. In other locations, steel plating of the concrete walls may be required to ensure ductility.
Structural design for catastrophic events can often present challenges to the design team. In the case of a high containment facility, this is further complicated by the typical day-to-day demands and the increased importance on the performance in the catastrophic event. With the collaborative effort of the design and construction team, such facilities can be built with confidence to deliver essential operation capabilities to study pathogens while protecting the public from danger.
