Impact of Class II Biological Safety Cabinet Downflow Velocity on Cross Contamination

Over the last several years, Biological Safety Cabinet (BSC) manufacturers have lowered downflow velocity while maintaining inflow velocity in an effort to increase energy efficiency, reduce exhaust system requirements and lower BSC Noise and vibration levels. However, the lowering of downflow velocity may come with a consequence of greater lateral airflow movement within the workzone creating greater potential for cross contamination. This application note from NuAire addresses the question, how low can a downflow average be, before it causes cross contamination according to industry standard work practice guidelines? The use of a modified NSF/ANSI 49 cross contamination test method is described and the results indicate greater lateral airflow movement with lower average downflow velocities.