38 Biosafety Manual to NSF/ANSI 49-2019. • Any connections to exhaust duct work must allow access for field testing of exhaust flow according to NSF/ANSI 49-2019. • If the BSC is a Class II Type A2, the connection to the exhaust must be a canopy connection and not a gas-tight connection. There must be an alarm to indicate insufficient airflow through the canopy. For additional details about choosing appropriate BSCs and their proper use, see Appendix A to the BMBL: “Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets. Facility Design (Secondary Containment) Laboratories intended for work with biohazardous materials are designed to contain those materials in the laboratory so that they cannot cause harm to the general public or the environment. If a laboratory is to be used for work with recombinant or synthetic nucleic acid molecules, human, animal or plant pathogens, or biological toxins, it must meet certain federal criteria regarding appropriate containment facilities for the specific work to be done. The level of work that a laboratory is qualified to do is referred to as the biosafety level. There are four defined biosafety levels for work with human pathogens: BSL-1, BSL-2, BSL-3, and BSL-4. Materials requiring BSL-4 facilities and practices are not used at Iowa State University. The BMBL describes the criteria for the different biosafety levels in detail. The BMBL -Appendix A, “Primary Containment for Biohazards: Selection, Installation, and Use of Biological Safety Cabinets.” describes additional criteria for work with recombinant or synthetic nucleic acid molecules. A brief overview of biosafety level criteria is given in Biosafety Practices and Procedures. of this manual. The IBC and regulatory agencies require that work with animal or plant pathogens be conducted with comparable biocontainment facilities and biosafety practices.