Collison 6-jet nebulizer: choice for the certification test of the class II biological safety cabinet

Three types of nebulizers, one plastic, one glass and Collison 6-jet nebulizers were tested, to select an appropriate nebulizer for the certification of the class II biological safety cabinets (BSC). Performance of the plastic and glass refluxing nebulizers were found to be both inconsistent from one to another, and not provide reproducible results. The Collison nebulizers, on the other hand, showed little variations and provided reproducible results. In addition, the Collison nebulizer generated constant spray volume when the fluid level in the reservoir was varied. To determine optimum discharge velocity of the Collison nebulizer, nebulizers with an outlet diameter of 10, 12, 14, 16 and 18 mm were tested. For the personnel protection test, the main stream of aerosol sprayed from the Collison nebulizer with 14 mm outlet internal diameter hit the intersection of the test cylinder and the front opening. Each nebulizer with an outlet diameter of 12 to 16 mm located at the level of lower edge of the front window delivered aerosols more efficiently at the intersection than when located at 14 inches above the work surface. The aerosol from the 10 or 18 mm diameter nebulizers showed an inappropriate distribution. For the product protection test, the nebulizer with 14 mm outlet diameter showed the best distribution pattern around the test cylinder. In the cross contamination test, this nebulizer outperformed the 10 or 18 mm for class II BSC's without side wall effect. According to these results, the Collison nebulizer with 14 mm of internal diameter nozzle was found appropriate for the biological certification tests of the class II BSC. Exception was the cross contamination test of class II BSC with a side air intake between the internal side wall and the work surface, in which the nebulizer with 10 mm nozzle was the choice.