Share thisThe October 2010 column discussed the design principles and practical considerations that govern the performance of containment barriers in BSL-3 laboratory and animal facilities. It provided the safety rationale and operational considerations used to assess the appropriate barrier system specifications for different scientific activities and facility operations. The article outlined: the performance criteria and justification for making containment barriers airtight, impervious, chemically and mechanically resilient for safety; maintainability, and cost. Within those considerations, special attention was given to the question of air leakage; all biocontainment guidelines and inspection documents require airtight containment boundaries. The reasons are partly obvious—the need to prevent the escape of airborne hazards—and partly not so obvious; the most likely dangerous airborne agent in a BSL-3 room and the biggest challenge to contain are decontamination gas or vapors (in most cases).
In theory, the air impermeability of the containment room system (barrier integrity) is straightforward. In practice, things can and often do go sideways in the transition from concept to implementation of this basic containment barrier requirement. The BMBL’s sparse language (amplified by a lack of verification criteria in our licensing inspection protocols) is without question open to interpretation. This lack of definition or direction has caused a history of problems and less than optimum results in the construction of containment laboratories—costing facility owners money, loss of research opportunity, and certification “hardship.”
How do we manage these risks effectively? As with most things, early prevention is the best cure.
The Status Quo: Open to Interpretation
The BMBL gives very little guidance to the appropriate level of BSL-3 containment barrier integrity, sparsely stating: (the laboratory) “surfaces should be sealed” and “openings should be capable of being sealed to facilitate space decontamination.” In addition, there are no criteria for verifying that these conditions have been achieved in the BMBL or in any official certification checklist for BSL-3. Official inspection criteria, if they say anything, only require a visual inspection to validate a containment boundary is sufficiently airtight. But it’s impossible to see microscopic and hidden air leakage pathways; this method of validation cannot provide accurate or adequate quality assurance for these important construction criteria. It often can produce the perfect storm: a lack of defined performance measures or validation criteria with huge variability in how much or how little we can build/spend to achieve what we think are the appropriate results. This often means owners not getting what they’ve paid for or constructors having to unfairly spend more time and effort than they reasonably budgeted for chasing undefined acceptance criteria. I won’t comment on which scenario is more common.
Before we present alternate strategies and recommendations for barrier integrity assurance, we should defend the status quo (ambiguity) on one level: open to interpretation can be a good thing when it means that the answer is context-based and derived from risk assessment. “Capable of being sealed to facilitate space decontamination” can vary from application to application and with operational parameters such as decontamination frequency, timing, the proximity of occupied zones to the decontamination zone, the pressure relationships during fumigation that could induce gases to migrate, and research programs that have to remain in operation while the fumigation process is occurring (i.e. an animal experiment in an adjacent suite). An airlock on the boundary of an operating BSL-3 suite where equipment will be frequently decontaminated should be capable of being sealed very gas tight, even if the procedure will occur during unoccupied (night) hours. Conversely, I have worked with owners who appropriately decided to construct certain containment zones less gas tight than normal after careful risk assessment that determined aerosol release or significant accident with infectious material was extremely unlikely (based on special protocols) and their acceptance that, in the unlikely event that this space had to ever be fumigated, the entire building would remain empty as long as required. This was not a cost driven decision but instead was based on the user requirements activity type for the space, which made it unfeasible to construct to normal containment integrity standards (and unnecessary).
Quantitative and Qualitative Validation
The question still remains: for BSL-3 containment, how sealed is sealed?
We aren’t sure, frankly.