Biological safety levels refer to the lethality that a microorganism has. It goes for the lower fatal risk to highest. Microorganisms labeled under BSL-1 are low risk pathogens, that do not require several equipment for their management in the laboratory. BSL.2 microbes are mid-risk pathogens that require the use of equipment, such as face shields and two-door lab, in order to prevent infections. BSL-3 microbes are high-risk pathogens that require several and stringent measures in the lab. Lastly, BSL-4 microbes are pathogens that are usually fatal, so they require astringent protocols of hygiene and specialized laboratory equipment for their management.