Support & Guidance

Biosafety Level
Classification

Biosafety Levels (BSL) define the containment precautions required when handling biological materials. Classification is based on risk assessment, transmission routes and potential impact on human health.

BSL 1–4

RISK CLASSIFICATION

Biosafety Levels

Four ascending levels of containment, from basic to maximum security

BSL-1

Minimal Risk

Agents not known to consistently cause disease in healthy adults.

Required Practices

Standard microbiological practices
Work on open bench tops
No special containment equipment required
Lab coats and gloves as needed

Example Agents

E. coli K-12, Bacillus subtilis, S. cerevisiae

BSL-2

Moderate Risk

Agents associated with human disease presenting moderate hazards.

Required Practices

Limited laboratory access
Biohazard warning signs posted
Biosafety cabinets for aerosols
Decontamination of infectious waste

Example Agents

Hepatitis B, HIV, Salmonella, MRSA

BSL-3

High Containment

Agents that may cause serious or potentially lethal disease via inhalation.

Required Practices

Controlled access
All work in biosafety cabinets
Respiratory protection
Separated laboratory environment

Example Agents

M. tuberculosis, SARS-CoV, West Nile Virus

BSL-4

Maximum Containment

Dangerous and exotic agents with high risk of life-threatening infection.

Required Practices

Positive-pressure suit
Dedicated ventilation systems
Full decontamination procedures

Example Agents

Ebola virus, Marburg virus, Nipah virus

AT A GLANCE

Safety Requirements Comparison

Requirement	BSL-1	BSL-2	BSL-3	BSL-4
Open Bench Work	✔	–	✕	✕
Biosafety Cabinet Required	✕	✔	✔	✔
Restricted Access	✕	✔	✔	✔
Decontamination of Waste	✕	✔	✔	✔
Controlled Ventilation	✕	✕	✔	✔
Double-Door Entry	✕	✕	✔	✔
Full Pressure Suit	✕	✕	✕	✔
Chemical Shower Exit	✕	✕	✕	✔