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News about laboratory biosafety
April 24, 2019

Dr Richard W Gilpin RBP CBSP SM(NRCM) 

Author, Public Speaker, Biosafety Trainer, Former Medical School Faculty
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Photo: NSF International Standard 49-2018 Annex E

Excerpt from NSF 49 - 2018 Annex E - Page 8:
If the exhaust system malfunctions, do you know whether Type A2, B1, B2, or C1 BSC's maintain worker protection?

Type A BSC with a canopy connection to the laboratory exhaust system: Yes
Reduction or elimination of the exhaust air should not significantly affect the airflow patterns within the BSC. Personnel and production protection of the BSC will remain unchanged; however, chemical vapors generated in the BSC will be exhausted into the laboratory via the openings or slots in the exhaust canopy. 

Type B1 or B2 BSC with a direct connection to its dedicated exhaust system: No
Significant loss of exhaust airflow will result in an alarm, turning off the cabinet blower(s). This stops the flow of air into the front of the BSC (inflow), negating personnel protection, potentially allowing materials in the work area of the BSC to escape into the laboratory.

Type B BSCs have operational and maintenance issues that must be considered: These cabinets exhaust as much as 1200 cubic feet per minute of conditioned room air making them relatively expensive to operate; and the higher static air pressure required to operate Type B cabinets may also result in additional construction costs associated with heavier gauge ductwork and higher capacity exhaust fan.

Type C1 BSC with a canopy connection to the laboratory exhaust system: Yes
Reduction or elimination of the exhaust air should not significantly affect the airflow patterns within the BSC while its blowers are in operation. Personnel and product protection of the BSC will remain unchanged, and chemical vapors generated in the BSC will be exhausted either back into the room, or into the exhaust system, depending on the configuration of the canopy.

If a Type C1 BSC directs its exhaust into the room during a system failure, the shutdown time of the BSC blowers can be lengthened from 15 seconds to up to 5 minutes.

If a Type C1 BSC directs its exhaust into the external exhaust system during a system failure, the default shutdown time of the BSC blowers can be lengthened from 15 seconds to up to 5 minutes, provided: a risk assessment indicates the BSC, the work being done in it, and the exhaust system it is connected to is appropriate; and the BSC is connected to an exhaust duct that has been verified to meet or exceed Seal Class A, as described in HVAC Air Duct Leakage Test Procedures.

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Dr Richard W Gilpin RBP CBSP SM(NRCM) - April 24, 2019

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