Abstract
NSF International Standard 49–1992, that covers certification of biological safety cabinets, makes “special note” that a “stainless steel 6-jet Collison refluxing nebulizer will deliver the [required] bacterial spore aerosol” when certain stated conditions are met and “need not be retested for performance before use” (Appendix-C, page C1) (1). The basis on which this nebulizer was vetted was presented at the XXV Biological Safety Conference (Boston, MA, 1984) but never published in the open literature. In view of the importance of this device for the procedures used to certify the performance of biological safety cabinets, the authors are of the opinion that the test protocols and test data on which the selection was based should be made a matter of record.
Collison nozzle studies were conducted to determine (a) whether all 6 Collison nozzles manufactured by BGI give the same spore output when operated at 140 kPa (20 psig) with an equal number spore suspension in the flask (b) whether spore delivery by the 6-jet Collison nozzle equals or exceeds the minimum number specified by NSF 49 when charged with the recommended spore suspension (c) whether performance of Collison nozzles with a bacterial spore aerolsol can be predicted accurately with a monodisperse 1.1 μm polystyrene latex spherical simulant, and (d) the optimum nebulizer flask geometry.