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Biological Safety Cabinets

Biological Safety Cabinets

Biological Safety Cabinets

Simulation and Quantifying of Airflow Perturbation Caused by Personnel Activities

Applied Biosafety: Journal of ABSA International 1-7

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Abstract

It is a well-known fact that personnel activities can have an adverse effect on the protective functions of biological safety cabinets. Increased air turbulence within the work area or within the surrounding room can disrupt the essential directional airflows of the cabinet, which generate the protective barrier between the environment and the products handled inside. This may result in an enhanced escape and/or invasion of airborne particles or microorganisms. Nevertheless, manufacturers tend to reduce downflow and inflow velocities up to the limits of the allowed values to improve energy efficiency or to reduce noise and vibration. Reliable data based on standardized test procedures to estimate the consequences arising from these measures are rare. In this study, the influence of different static and dynamic disturbing factors on the personnel protection performance of 2 class II biological safety cabinets was quantified. A microbiological test procedure given by the relevant European and US standards (EN 12649, NSF/ANSI 49) was used, but in contrast to the low requirements defined there, 4 more complex and realistic test scenarios were chosen to simulate working activities: static covering of the front sash opening caused by a sitting or standing person was simulated by a “dummy worker” and a “body plate,” respectively. Dynamic airflow perturbations were generated by an artificial “moving arm” swinging regularly inside the cabinet and by a flat plate running outside the cabinet parallel to its front opening to simulate a “walking man”. It could be demonstrated that dynamic airflow disturbances caused by rapid body movements have a major impact on the cabinet’s protecting performance. Compared with an undisturbed working situation, personnel-protecting capabilities of both safety cabinets tested declined substantially when the worker’s movement next to the front opening was simulated. Therefore, downflow and inflow velocities should not be reduced to minimum values, to allow a sufficient margin of safety for actual in-use laboratory conditions (“disturbed”).

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