Which statement is a key practice at BSL-3 laboratories?

• A. Negative pressure with respiratory protection
• B. PPE and biosafety cabinet
• C. Full barrier suit and sealed facilities
• D. Standard precautions

Answer: (A)

Maintaining negative pressure with respiratory protection is the defining containment measure for BSL-3 labs. Keeping the workspace under negative pressure means air flows into the room rather than out to surrounding areas, so any aerosols or airborne contaminants generated during procedures are less likely to escape to adjacent spaces. This physical containment is essential for preventing exposure to workers and the environment. Respiratory protection adds another layer of defense, reducing the chance of inhaling any aerosols that might be generated or that could leak through gaps.

PPE and biosafety cabinets are important tools in a BSL-3 program, but they don’t establish the overall containment by themselves. A full barrier suit and sealed facilities imply a higher level of containment than standard BSL-3 and aren’t typical for all BSL-3 operations. Standard precautions are baseline practices used broadly and do not specifically address the airborne containment features required at BSL-3.