What Is Biological Safety Level? - Biosafety level 1 (BSL-1), level 2 (BSL-2), level 3 (BSL-3), level 4 (BSL-4)

  • 25, 06, 2021

1. What is biological safety level? 

Biological safety level or biosafety level is a series of biocontainment precautions intended to protect personnel from potentially hazardous biological agents exposure in a research or manufacturing environment.

Based on the agents or organisms researched or worked on in any given setting, there are 4 biological safety levels, with biosafety level 1 (BSL1) being the lowest and biosafety level 4 (BSL4) being the highest. 

2. Biological safety level 1 (BSL1)
  • Biological safety level 1 applies to the settings where personnel work with low-risk microbes that do not cause disease, such as E.coli. 
  • Work can be done on clean benches without the use of special contaminant equipment. 
  • At this level, minimal personnel protective equipment (PPE), such as eye protection, gloves and a lab gown, is required. 
  • BSL-1 lab is separated from the surrounding facilities by doors. 

Image: Clean bench used in BSL-1 lab

3. Biological safety level 2 (BSL2)
  • Biological safety level 2 applies to the settings where personnel work with agents associated with human diseases that are moderately hazardous, such as equine encephalitis viruses and HIV, as well as Staphylococcus aureus (staph infections). 
  • Access to a BSL-2 lab is more restrictive than a BSL-1 lab. The lab is restricted behind self-closing doors.
  • At this level, personnel wear is required to take greater care for those working in BSL-2 lab. 
  • Negative-pressure containment is generally advised, and exhausted air may require filtration.

4. Biological safety level 3 (BSL3)

  • Biological safety level 3 applies to the settings where personnel work with airborne microbes that can cause potentially lethal diseases, such as yellow fever and tuberculosis. 
  • Workers may require immunizations for microbes they work with. Personnel protective equipment plus respirators are required. 
  • All work with microbes must be performed within an appropriate biosafety cabinet.
  • Filtered room air must be exhausted

5. Biological safety level 4 (BSL4)

  • Biological safety level 4 applies to the settings where personnel work with highly dangerous and exotic microbes. Infections caused by these types of microbes are frequently fatal and come without treatment or vaccines. Two examples of such microbes include Ebola and Marburg viruses.
  • Decontaminate all material before exiting lab; shower after exiting.
  • Full body, positive-pressure cleanroom suit. All work performed in Class III Biosafety Cabinet (Isolator). Lab is in a separate building.


​​​​​​​Personnel at all BSL facilities are required to follow “standard microbial practices,” which include no food or drink, no cosmetics, frequent hand and glove washing, and routine decontamination of surfaces. Sterilization and entry/exit protocols differ depending on the BSL level.


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