Canopy-connected Type A2 BSCs can handle most quantities of volatile chemicals used in biomedical research, in my opinion.
Scroll to the bottom to get formulas to calculate acceptable quantities of volatile chemicals in BSCs from The Baker Company:
Statements from NSF/ANSI 49 – 2020 Informative Annex 1: Biosafety cabinet selection, installation, lifespan and decommissioning.
© 2021 NSF: This document is publically available at no cost.
I-220.127.116.11 Question three: What types and quantities of chemical vapors will be generated in the BSC?
As important as the preceding question, the user must also foresee the types and quantities of chemical vapors that will be generated in the cabinet. Because chemical vapors can freely pass through HEPA/ULPA filters, both Class I and Class II BSCs must be exhausted out of the laboratory when used with these types of chemicals. For the Class II BSCs, Types B1 and B2 must be direct connected to an external exhaust system in order to operate properly; Types A1, A2, and C1 can be converted to operate in either a canopy ducted or recirculating mode, depending on the users’ requirements. The airflow patterns of Types A1, A2, B1, B2 and C1 BSCs are shown in Figures 35, 37, 38 and 40, respectively.
Class II BSCs typically do not feature explosion-proof electrical components in their total work area or internally. Therefore, use of flammable or explosive materials in quantities above their explosive limit are not recommended.
Types of chemicals used in cabinet should be considered as some can destroy the filter medium, housings and gaskets causing loss of containment.
The percentage of air in the total work area that is recirculated within the BSC versus exhausted varies, based on the BSC Type, subtype, and in some cases, where the chemicals are released in the total work area.
When flammable or explosive chemicals are to be used in a BSC, it is the users’ responsibility to:
— be fully cognizant with the properties of chemical(s) and the hazards associated with them;
— calculate the highest percent of recirculation that may occur in the BSC being used;
— ensure the concentration of chemical(s) released in the total work area do not exceed their explosive limit;
— utilize the lowest quantities of the chemical(s) required for the procedure being performed; and
— have appropriate spill / splash cleanup procedures in place before using the chemical(s).
Class II Biosafety Cabinet Type A1 and A2:
Work with volatile organic chemicals on the work surface permitted as an adjunct to microbiological research if the BSC is canopy-connected to external exhaust and permitted by risk analysis.
Class II Biosafety Cabinet Type C1:
Work with volatile organic chemicals on the work surface is permitted as an adjunct to microbiological research if the cabinet is connected to an exhaust system, and is acceptable after performing a risk analysis. Typically, a majority of the downflow air is directly exhausted from the center portion of the cabinet.
Class II Biosafety Cabinet Type B1:
Work with volatile organic chemicals on the work surface permitted as an adjunct to microbiological research if permitted by risk analysis. A majority of the downflow air is directly exhausted from the rear portion of the cabinet.
Class II Biosafety Cabinet Type B2:
Work with volatile organic chemicals on the work surface permitted as an adjunct to microbiological research if permitted by risk analysis. All downflow air is directly exhausted from the work area with no recirculation.
In my opinion, and as stated in Annex 1 exhaust failure section; Type B2 BSCs are the most dangerous cabinets because during exhaust failure – volatile organic chemicals in the work area are dumped into the worker’s breathing zone.
Volatile Chemicals in a Class II Type A2 “Recirculated” BSCs: How Much is Safe?
Kara F. Held, Ph.D., Dan Ghidoni, Gary Hazard, and David Eagleson. Baker Company. October 2016.
Using a Class II Type A2 4-foot Baker SterilGARD with an 8” access opening for the calculations, the amount of ethanol that can be released without an explosion is 64.2 ml per minute.
(That’s a lot of volatile organic!)