Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Biosafety Levels (BSLs) are standardized safety protocols used to contain infectious agents in laboratory settings. They range from BSL-1 to BSL-4, with increasing levels of containment and protection.
Biosafety Level 1 (BSL-1) is the lowest level, involving agents that pose minimal risk and do not consistently cause disease in healthy adults.
Biosafety Level 2 (BSL-2) includes agents that pose moderate hazards to personnel and the environment, such as Salmonella and Hepatitis B.
Biosafety Level 3 (BSL-3) is designed for work with agents that can cause serious or potentially lethal diseases through inhalation, like Mycobacterium tuberculosis.
Biosafety Level 4 (BSL-4) is the highest level of biocontainment, reserved for dangerous and exotic agents that pose a high risk of aerosol-transmitted infections, such as Ebola virus.
Each BSL has specific requirements for laboratory practices, safety equipment, and facility construction.