Engineering and microbiological tests indicated that a typical, commercial laminar airflow cabinet was not effective in providing either product protection or agent containment. The cabinet was modified and tested through a series of alternate configurations to establish a set of design criteria. A mock-up cabinet was developed from these design criteria. The mock-up unit was evaluated for efficiency in providing both product protection and agent containment. In these evaluations, challenge methods were developed to simulate normal, in-use laboratory operations. Controlled bacterial or viral aerosol challenges were used at higher than normal levels to provide stringent test conditions. Test results indicated that the mock-up unit was considerably better in preventing agent penetration (0.1 to 0.2 particles per 100 ft(3) of air) than the commercial cabinet (5 to 6 particles per 100 ft(3) of air) during product protection tests. Similarly, agent containment was considerably better in the new cabinet (particle escape of 2 to 3 per 100 ft(3) of air at only one of the five test sites) than in the commercial cabinet (particle escape of 2 to 14 per 100 ft(3) of air at three of the five test sites).