Online Resources
Share This Page
CDC & NIH Biosafety Levels
The Centers for Disease Control (CDC) and the National Institutes of Health (NIH) have established four biosafety levels consisting of recommended laboratory practices, safety equipment, and facilities for various types of infectious agents. Each biosafety level accounts for the following:
- Operations to be performed
- Known and suspected routes of transmission
- Laboratory function
The following sections discuss the Biosafety Levels:
Biosafety Level 1
Biosafety Level 1 precautions are appropriate for facilities that work with defined and characterized strains of viable organisms that do not cause disease in healthy adult humans (e.g., Bacillus subtilis and Naegleria gruberi). Level 1 precautions rely on standard microbial practices without special primary or secondary barriers. Biosafety Level 1 criteria are suitable for undergraduate and secondary education laboratories.
Biosafety Level 2
Biosafety Level 2 precautions are appropriate for facilities that work with a broad range of indigenous moderate-risk agents known to cause human disease (e.g., Hepatitis B virus, salmonellae, and Toxoplasma spp.). Level 2 precautions are necessary when working with human blood, body fluids, or tissues where the presence of an infectious agent is unknown. The primary hazards associated with level 2 agents are injection and ingestion. Most Texas State University - San Marcos research laboratories should comply with Biosafety Level 2 criteria.
Biosafety Level 3
Biosafety Level 3 precautions apply to facilities that work with indigenous or exotic agents with the potential for aerosol transmission and lethal infection (e.g., Mycobacterium tuberculosis). The primary hazards associated with level 3 agents are autoinoculation, ingestion, and inhalation. Level 3 precautions emphasize primary and secondary barriers. For primary protection, all laboratory manipulations should be performed in biological safety cabinet or other enclosed equipment. Secondary protection should include controlled access to the laboratory and a specialized ventilation system.
Biosafety Level 4
Biosafety Level 4 precautions are essential for facilities that work with dangerous and exotic agents with a high risk of causing life-threatening disease, the possibility of aerosol transmission, and no known vaccine or therapy (e.g., Marburg or Congo-Crimean viruses). Level 4 agents require complete isolation. Class III biological safety cabinets or full-body air-supplied positive-pressure safety suits are necessary when working with level 4 agents. In addition, isolated facilities, specialized ventilation, and waste management systems are required. There are no Biosafety Level 4 facilities at Texas State University - San Marcos .
| Safety Level | Agent Characteristics | Safety Practices | Primary Barriers | Secondary Barriers |
|---|---|---|---|---|
| 1 | Not known to cause disease in healthy adults. | Standard Microbiological practices | None | Open bench top sink required. |
| 2 | Associated with human disease. | Level 1 precautions +: | - Class I or II biological safety cabinet or other physical containment device | Level 1 precautions +: - Autoclave available |
| 3 | Indigenous or exotic agentwith the potential for aerosol transmission.
| Level 2 precautions +: | - Class I or II biological safety cabinet or other physical containment devices | Level 2 precautions +: - Physical separation from access corridors - Self-closing, double door access - Exhausted air not recirculated - Negative airflow into laboratory |
| 4 | Known to cause disease with serious or lethal consequences. dangerous/exotic agents which pose high risk of life-threatening disease and aerosol transmitted infection. Related agents with unkown risk of transmission. | Level 3 precautions +: - Clothing chnage before entering - Shower upon exit - All material decontaminated upon exit from facility | - All procedures conducted in Class III biological safety cabinets or in Class I or II biological safety cabinets with full-body, air-supplied, positive pressure personnel suits | Level 3 precautions +: - Seperate building or isolated zone - Dedicated supply/ exhaust, vacuum, and decontamination systems - Other requirements as necessary |
Animal Biosafety
Four biosafety levels are also described for infectious disease work with laboratory animals. Animal Biosafety Levels 1, 2, 3, and 4 designate safety practices, equipment, and facilities.
Refer to the Laboratory Safety chapter for more information regarding the use of hazardous materials with laboratory research animals.