Biosafety Level 4 (BSL 4) are designed and built for the highest level of biological safety. Laboratory work on EVD typically occurs in a BSL 4 facility.
There are four biosafety levels. Each level has specific controls for containment of microbes and biological agents. The primary risks that determine levels of containment are infectivity, severity of disease, transmissibility, and the nature of the work conducted. Origin of the microbe, or the agent in question, and the route of exposure are also important.
Each biosafety level has its own specific containment controls that are required for the following:
Laboratory practices Safety equipment Facility construction
If you work in a lab that is designated a BSL-1, the microbes there are not known to consistently cause disease in healthy adults and present minimal potential hazard to laboratorians and the environment. An example of a microbe that is typically worked with at a BSL-1 is a nonpathogenic strain of E. coli.
Specific considerations for a BSL-1 laboratory include the following:
Standard microbiological practices are followed. Work can be performed on an open lab bench or table. Safety equipment
Personal protective equipment, (lab coats, gloves, eye protection) are worn as needed. Facility construction
A sink must be available for hand washing. The lab should have doors to separate the working space with the rest of the facility.
BSL-2 builds upon BSL-1. If you work in a lab that is designated a BSL-2, the microbes there pose moderate hazards to laboratorians and the environment. The microbes are typically indigenous and associated with diseases of varying severity. An example of a microbe that is typically worked with at a BSL-2 laboratory is Staphylococcus aureus.
In addition to BSL-1 considerations, BSL-2 laboratories have the following containment requirements:
Access to the laboratory is restricted when work is being conducted. Safety equipment
Appropriate personal protective equipment (PPE) is worn, including lab coats and gloves. Eye protection and face shields can also be worn, as needed. All procedures that can cause infection from aerosols or splashes are performed within a biological safety cabinet (BSC). An autoclave or an alternative method of decontamination is available for proper disposals. Facility construction
The laboratory has self-closing doors. A sink and eyewash are readily available.
BSL-3 builds upon the containment requirements of BSL-2. If you work in a lab that is designated BSL-3, the microbes there can be either indigenous or exotic, and they can cause serious or potentially lethal disease through respiratory transmission. Respiratory transmission is the inhalation route of exposure. One example of a microbe that is typically worked with in a BSL-3 laboratory is Mycobacterium tuberculosis, the bacteria that causes tuberculosis.
In addition to BSL-2 considerations, BSL-3 laboratories have the following containment requirements:
Laboratorians are under medical surveillance and might receive immunizations for microbes they work with. Access to the laboratory is restricted and controlled at all times. Safety equipment
Appropriate PPE must be worn, and respirators might be required. All work with microbes must be performed within an appropriate BSC. Facility construction
A hands-free sink and eyewash are available near the exit. Exhaust air cannot be recirculated, and the laboratory must have sustained directional airflow by drawing air into the laboratory from clean areas towards potentially contaminated areas.
Entrance to the lab is through two sets of self-closing and locking doors.
BSL-4 builds upon the containment requirements of BSL-3 and is the highest level of biological safety. There are a small number of BSL-4 labs in the United States and around the world. The microbes in a BSL-4 lab are dangerous and exotic, posing a high risk of aerosol-transmitted infections. Infections caused by these microbes are frequently fatal and without treatment or vaccines. Two examples of microbes worked with in a BSL-4 laboratory include Ebola and Marburg viruses. In addition to BSL-3 considerations, BSL-4 laboratories have the following containment requirements:
Change clothing before entering. Shower upon exiting. Decontaminate all materials before exiting. Safety equipment
All work with the microbe must be performed within an appropriate Class III BSC , or by wearing a full body, air-supplied, positive pressure suit. Facility construction
The laboratory is in a separate building or in an isolated and restricted zone of the building. The laboratory has dedicated supply and exhaust air, as well as vacuum lines and decontamination systems.