Exhausting of a Class II, Type A2 Biological Safety Cabinet (BSC)

By NuAire

NuaireWhile searching for that extra degree of safety in your laboratory or trying to remove fumes/gases from the laboratory environment NuAire has the proper canopy connections to exhaust your Class II, Type A2 Biological Safety Cabinet.

Canopy Exhaust Transitions
Canopy Transitions provide an air gap between the exhaust efflux of the BSC and the transition. The air gap essentially insulates the BSC from potential variations of airflow in the facility exhaust system, particularly if multiple BSC’s are connected to the same exhaust blower system.

NuAire’s Variable Flow Canopy (VFC) employs adjustable slide plates [A] to vary slot height corresponding to the amount of room exhaust volume desired. Upon canopy low flow or loss of exhaust, the integrated airflow monitor [B] will provide both an audible and visual alarm, and then energize a DC solenoid [C] opens the front panel allowing the BSC inflow to be maintained at NSF recommended inflow velocities.

VFCVFC Integration into a Laboratory Mechanical Design
Traditionally, exhaust canopies using a fixed slot area provided a fixed exhaust volume requirement that was added to the cabinet exhaust volume for the total exhaust volume requirement used for the laboratory mechanical design. However, now the VFC has variable slot areas, so the exhaust requirement that is added to the cabinet exhaust volume for the total exhaust volume requirement is also variable for the laboratory mechanical design. With the VFC offering a range of exhaust volume possibilities, the question becomes, what exhaust volume should be designed into the laboratory mechanical system? Traditionally, exhaust canopies were designed to exhaust approximately 25% more air volume that the cabinets exhaust volume. The VFC now can be used with as little as 5% more or up to 100% more in some cases depending upon cabinet size. The answer to the above question becomes one of what produces the optimal mechanical design. Laboratory size, pressure, air change rate, heat load and other exhausting devices can all have an impact on the designed exhaust volume of the VFC.

If it is found that there is not a specific exhaust requirement, then it is suggested to use a target canopy air volume (i.e. 100 cfm plus cabinet exhaust volume) that offers the ability for on-site adjustment (slot area on canopy) for optimal capture velocity (i.e. 200 fpm). If energy efficiency is desired, then use the minimum canopy air volume (i.e. 25 cfm plus cabinet exhaust volume). The real benefit of the VFC is the adjustability both through the design and installation phases. It will provide the mechanical designer flexibility to specify to the optimal exhaust flow volume for the application. It will also let the installer/certifier field adjust to assure the proper capture slot velocity.

The characteristics of VFC Canopy are as follows:
• Preserves airflow balance within the BSC in a simple dependable manner.
• Has a front service panel to permit exhaust HEPA filter integrity checks.
• Simplifies exhaust system design.
• Provides the adjustability for the amount of laboratory air exhausted whether more for general exhaust or to limit loss of conditioned air for greater energy efficiency.
• Integrated audible and visual low exhaust alarm.
• Provides a safety operational tolerance range for normal exhaust system fluctuations.

VFC CanopyFor full information on how to apply the VFC to your BSC Contact NuAire at: 800-328-3352 or visit www.nuaire.com

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Published: November 2, 2012

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