Biosafety Level 1, 2, 3 and 4 with comparison

Biosafety Level 1, 2, 3 and 4

  • The handling of pathogenic microorganisms is a highly challenging job due to the chances of contamination.
  • Moreover, pathogens involve in causing the disease to a host. Bio-safety is a concept by which a person can take necessary precautions against infectious agents in a laboratory environment.
  • Bio-safety level refers to a series of precautions that are taken to handle the pathogens.
  • The concept of the Bio-safety Level differs in different countries.
  • The Centers for Disease Control and Prevention(CDC), USA, divided the Bio-safety level into four parts on the basis of the pathogenicity of the organism.
  • The lowest level is known as Bio-safety level 1 (BSL-1) and Bio-safety level 4 (BSL-4) for the highest level.
  • On the other hand, the European Union has also categorized the Bio-safety levels and it is termed as ‘directive’ and in Canada, it is known as ‘Containment Levels’.

Biosafety Level 1, 2, 3 and 4

Image Source: Lab Manager.

The four different Bio-safety levels are described as following

Biosafety Level 1

Biosafety level 1 is designed to work with microbes that are non-pathogenic or may have a low risk of causing an infection. An example of one such kind of microorganism is E. coli.

Specific considerations

  • Due to the absence of pathogenic organisms, BSL-1 follows the basic rules and regulations of a laboratory.
  • Work can be performed at open tables.
  • Personal Protective Equipment (PPE) includes lab coats, gloves, eye guard (in some cases).
  • Hand washing by using soap and the use of hand sanitizers are essential things.
  • The working space of the lab should be separated from the rest of the facilities.

Biosafety Level 2

All the necessary actions taken in BSL-1 are also followed in BSL-2 along with some additional precautions.

  • The person who is handling the microbes needs to have specific training under the guidance of scientists with an advanced research background.
  • The entry and exit of a BSL-2 lab need to be strictly monitored.
  • All the works need to be performed inside a bio-safety cabinet to avoid contamination.
  • The use of masks as a PPE is necessary.
  • A laboratory with self-closing doors are required.

BSL-2 deals with moderate pathogens which can cause mild disease to the human host. The organisms include Hepatitis A, Hepatitis B and Hepatitis C viruses, Plasmodium falciparum, Salmonella Typhi, Staphylococcus aureus, etc.

Biosafety Level 3

The microbes used in BSL-3 are highly contagious through respiratory transmission and can also cause serious damage to the human host. An important example of this type of microorganism is Mycobacterium tuberculosis, the causative agent of the disease called tuberculosis.

Along with the BSL-2 system, BSL-3 has several important considerations such as

  • People working in the laboratory are under medical surveillance and immunization is required for those people.
  • Access to the laboratory needs to be restricted and monitored.
  • Appropriate PPE is required along with respirators.
  • All the works need to be performed inside a bio-safety cabinet.
  • Hands-free sink along with eyewash facility is necessary.
  • Air circulation needs to be maintained inside the lab.
  • The entry point needs to have two sets of self-closing doors.

Biosafety Level 4

BSL-4 is the highest level to provide necessary precautions from pathogenic microbes. The microbes which come under BSL-4 are dangerous and can lead to aerosol transmitted infection. Infections due to these microbes are generally fatal and vaccines or appropriate treatment are required. An example of BSL-4 microorganism is the Ebola Virus.

Like the other three safety levels, BSL-4 also consists of all the precautionary measures from its previous safety level (BSL-3) along with some specific considerations.

  • People working in the lab need to change their clothes before entering.
  • Systems need to be installed by which laboratory experts can use a shower upon exiting.
  • Decontamination of all the materials needs to be performed before exiting.
  • PPE, in this case, is a full-body suit with proper eye gear and masks.
  • The laboratory needs to be isolated from other buildings.
  • Along with proper air circulation system the laboratory needs to have an adequate decontamination system.

Comparing Biosafety Level 1, 2, 3 and 4

Comparing Biosafety Level 1, 2, 3 and 4

Image Source: Consolidated Sterilizer Systems.


Centers for Disease Control and Prevention:


  • 2% –
  • 2% –
  • 1% –
  • 1% –
  • 1% –
  • <1% –
  • <1% –

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