Which statement best describes Biosafety Levels (BSL) used for handling biological agents?

• A. BSL-2 is the lowest level; BSL-4 is not used.
• B. BSL-1 to BSL-4 exist, with increasing containment and practices.
• C. BSL refers to administrative controls.
• D. BSL-1 through BSL-3 are used for chemical hazards.

Answer: (B)

Biosafety levels are a ladder of containment that matches how risky a biological agent is to people and the environment. Each level specifies the required lab practices, safety equipment, and facility design, becoming more stringent as the hazard increases. There are four levels, from the lowest through the highest, with higher levels adding more containment features, tighter access, and more protective PPE. This is why the statement describing BSL-1 to BSL-4 with increasing containment and practices is the best fit. For example, BSL-1 covers safe, nonpathogenic organisms; BSL-2 adds demonstrations of safer handling and limited access; BSL-3 uses sealed spaces with negative pressure and enhanced respiratory protection; BSL-4 involves full isolation and specialized suits for the most dangerous agents. The concept focuses on biological risk and the corresponding containment, not administrative controls alone or chemical hazards.