| BSL | Agents | Practices | Safety Equipment (Primary Barriers) |
Facilities (Secondary Barriers) |
| 1 | Not known to consistently cause disease in healthy adults | Standard Microbiological Practices | None required | Open bench top sink required |
| 2 | Associated with human disease, hazard: percutaneous injury, ingestion, mucous membrane exposure |
BSL-1 practices plus: Limited access |
Primary barriers: Class I or II BSCs or other physical containment devices used for all manipulations of agents that cause splashes or aerosols of infectious materials. PPEs: laboratory coats, gloves, face protection as needed | BSL-1 plus: Autoclave available |
| 3 | Indigenous or exotic agents with potential for aerosol transmission; disease may have serious or lethal consequences |
BSL-2 practices plus: Controlled access |
Primary barriers: Class I or II BSCs or other physical containment devices used for all open manipulations of agents; PPE: protective lab clothing, gloves, respiratory protection as needed | BSL-2 plus: Physical separation from access corridorsSelf-closing, double-door accessExhausted air not recirculatedNegative airflow into laboratory |
| 4 | Dangerous/exotic agents which pose high risk of life-threatening disease, aerosol-transmitted lab infections; or related agents with unknown risk of transmission | BSL-3 practices plus: Clothing change before enteringShower on exitAll material decontaminated on exit from facility | Primary barriers = All procedures conducted in Class III BSCs or Class I or II BSCs in combination with full-body, air-supplied, positive pressure personnel suit | BSL-3 plus: Separate building or isolated zone Dedicated supply and exhaust, vacuum, and decon systems. Other requirements outlined in BMBL. |