Define biosafety levels (BSL) and give a characteristic of BSL-2 and BSL-3.

• A. BSLs categorize containment for biosafety. BSL-2 involves limited lab access and PPE for handling pathogens; BSL-3 requires controlled access, negative pressure, and specialized PPE for handling more dangerous agents.
• B. BSLs are used to classify chemical hazards; BSL-2 uses open benches; BSL-3 uses no PPE.
• C. BSL stands for Basic Safety Level, unrelated to lab containment.
• D. BSLs apply only to fieldwork; lab settings do not use BSL.

Answer: (A)

Biosafety levels define the containment and safety practices required for working with biological agents to protect people and the environment. For BSL-2, the focus is on handling pathogens that pose a moderate risk. Work areas have limited access to trained personnel, and personal protective equipment such as gloves, lab coats, and eye/face protection are used. Procedures that could generate aerosols are performed with appropriate containment, and basic biosafety cabinets or other barriers are used as needed.

For BSL-3, the requirements step up for more dangerous agents. Access to the lab is tightly controlled, the facility uses controlled airflow with negative pressure so air flows into the room and not out to other areas, and highly specialized PPE is required, often including respirators. Engineering controls and strict entry/exit procedures are implemented to prevent release of the agent.

These points distinguish biosafety levels as containment standards in laboratory settings, rather than classifications of chemical hazards, and they aren’t limited to fieldwork.