A microbiological safety cabinet was evaluated to determine conditions under which microorganisms might escape. Tests were conducted under three cabinet-closure conditions, various airflow velocities, and different laboratory operations, with 105, 1.1 × 105, and 106 microorganisms per cubic foot of cabinet space released per min for 5 min. The data revealed that (i) escape of a human infectious dose is possible when the cabinet is used with the glove panel off; (ii) the number of organisms that escaped from the cabinet increased with a decrease in air velocity; and (iii) an increase in the number of laboratory operations resulted in an increase in the number of organisms that escaped. Thus, when the glove panel was off, the cabinet was only safe for operations that released a small number of microorganisms into the cabinet, whereas the cabinet was safe for operations of significantly greater hazard when used with the glove panel on but with the gloves unattached.
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