Evaluating containment effectiveness of A2 and B2 biological safety cabinets

This study investigates the use of a canopy-connected recirculating class II type A2 biological safety cabinet (BSC) as an alternative to the B2 when preparing volatile, sterile compounded preparations. Selection of the appropriate BSC for processes that use subgram levels of volatile chemicals is difficult due to a lack of quantitative containment evidence by cabinet type. There is a perception that hazardous compounding must be done in a B2 cabinet due to the potential for vapors, and this study seeks to challenge that perception.

In total, 5 tests, 3 prequalification tests and 2 containment capability tests, were conducted on a single cabinet of each type at sterile compounding pharmacies. Prequalification tests were performed to verify that each BSC was operating properly. Each cabinet was certified to NSF-ANSI 49-2016, particle counted per ISO 14644-1:1999, and subjected to a qualitative video smoke study. Once these tests confirmed the expected working conditions, 2 containment capability tests were conducted. The containment testing included tracer gas testing per ASHRAE 110:2016 section 8.1.1 through 8.1.13, and cyclophosphamide sampling during sterile compounding of the drug material.

Both cabinets passed all the prequalification tests. During the ASHRAE tracer gas testing the A2 cabinet was able to contain a tracer gas 92% to 160% as effectively as the B2 cabinet depending on the position of the gas ejection. During sterile compounding the airborne cyclophosphamide sampling captured samples of less than 1.0 ng at all locations for both the A2 and B2 cabinets.

The data generated from this study demonstrate that use of an A2 for hazardous compounding can provide a comparable level of safety for the environment, users, and product while having less stringent airflow requirements relative to a B2. The simpler requirements for an A2 make them an appealing alternative as they have the potential to reduce the overall operating costs associated with a compounding pharmacy while maintaining safe levels of containment.