What Are the Biohazard Safety Levels?

Biohazards are chemical or biological substances that are dangerous to the environment, humans or animals. These substances are categorized into four different biohazard safety levels (BSL) ranging from BSL-1 to BSL-4.

Each biosafety level uses distinct control procedures for microbial and biological agent containment. Developed for use in enclosed laboratory facilities, biohazard safety levels help reduce lab technicians’ and researchers’ risk of exposure to potentially infectious material (PIM). It is important to note, however, that lab technicians are not the only individuals who are at risk of potential biohazard exposure. Crime scene investigators and other members of law enforcement, healthcare professionals, and bioremediation specialists should also be cautious when handling blood and PIMs.

What Determines an Agent’s Biosafety Level?

According to the Center for Disease Control (CDC), “The primary risks that determine levels of containment are infectivity, severity of disease, transmissibility, and the nature of the work conducted.” Other factors that are important in determining biosafety levels include the origin of the microbe or agent and the route of exposure.


A Closer Look at Biohazard Safety Levels

Biosafety Level 1 (BSL-1) Microbes that are considered to be BSL1 are not known to cause disease in healthy adults and therefore present minimal health or safety risks to laboratorians. BSL Safety Requirements:

  • Individuals should wear personal protective equipment (PPE).
  • Individuals should have access to a hand washing sink.
  • The laboratory should have doors separating the workspace from other areas of the facility.

Biosafety Level 2 (BSL-2) Microbes that are considered to be BSL-2 pose a moderate risk to laboratorians. Examples of BSL-2 microbes are HIV and hepatitis B. BSL-2 Safety Requirements:

  • Individuals should wear PPE.
  • Individuals should have access to a hand washing sink and eye wash station.
  • The facility should have self-closing laboratory doors.

Biosafety Level 3 (BSL-3) Microbes that are considered to be BSL-3 can cause serious or potentially lethal disease through respiratory transmission. An example of a BSL-3 microbe is Mycobacterium tuberculosis (the bacteria that causes tuberculosis). BSL-3 Safety Requirements:

  • Individuals should wear PPE and respirators.
  • Individuals should have access to a hands-free sink and eyewash station.
  • The lab should have a double set of self-closing and locking doors with restricted or controlled access at all times.

Biosafety Level 4 (BSL-4) The microbes that are considered to be BSL-4 pose a high risk of aerosol-transmitted infections. According to the CDC, “Infections caused by these microbes are frequently fatal and without treatment or vaccines.” Examples of BSL-4 microbes include Marburg viruses and Ebola. BSL-4 Safety Requirements:

  • Individuals should change clothes before entering the lab and wear a full body, air supplied, positive pressure suit.
  • Individuals should shower upon exiting the lab.
  • The lab should be in an isolated or restricted zone of the building and should have dedicated supply and exhaust air.

Remember: potential biohazards are not only found in labs. Hepatitis B and HIV (BSL-2 agents), for instance, can be found in the blood or body fluids left at a crime or trauma scene. Aftermath, a professional bioremediation company, approaches crime and trauma scene cleanup with the four biohazard safety levels in mind. When handling blood and other PIMs, our technicians wear biohazard suits, respirators, and other personal protective equipment, and ensure every site is completely sanitized through a rigorous ATP fluorescence testing process. It’s too risky to cleanup potentially infectious materials on your own. Call Aftermath today for assistance.



Center for Disease Control: http://www.cdc.gov/training/QuickLearns/biosafety/

Food Safety Magazine: http://www.foodsafetymagazine.com/magazine-archive1/junejuly-2007/atp-systems-help-put-clean-to-the-test/