The effectiveness of the Duo-Flo BioClean unit for controlling airborne antigen levels

The Duo-Flo BioClean unit, consisting of a chamber unit with an animal rack, a HEPA filtration system, an air plenum, and a blower, was evaluated as a control unit for airborne rat antigen levels in the room housing the unit. The unit was evaluated in negative and positive pressure operating modes. In the negative mode, room air is drawn into the unit, passes over the animal cages, and is then exhausted into the room through the filters. In the positive mode, air passes through the filters, traverses the animals, and then is discharged into the room. Airborne antigen concentrations (ng/m3) and particle size distributions associated with antigen were measured during the two operating modes and prior to operation (background mode). Airborne antigen concentrations during the positive pressure operating mode were higher than during the negative pressure mode or background. Approximately 70% of airborne antigen was associated with respirable particles during background and positive pressure operating modes. A total of 36% of airborne antigen mass was associated with respirable particles during negative pressure operation. The unit is usually operated in the positive mode to protect experimental animals. This study clearly indicates that negative pressure operation would reduce the dispersion of dust-containing antigen, the exposure of room occupants to airborne antigen, and the risk to many workers of contracting animal allergy.