There are four biosafety containment levels (BSLs) that define proper laboratory techniques, safety equipment, and design, depending on the types of microbes or agents being studied. Where a microbe is confined is based on the degree of hazard posed by the microbe:
• BSL-1 labs are used to study microbes that don’t normally cause disease in healthy adults. They follow basic safety procedures and require no special equipment or design features.
• BSL-2 labs are used to study microbes that can infect humans if accidentally inhaled, swallowed, or enter the skin, but don’t usually cause serious disease. All of these diseases can be cured because there is an existing vaccine or treatment. Safety measures include the use of gloves and eyewear as well as hand washing sinks and waste decontamination equipment like autoclaves (sophisticated pressure cookers).
• BSL-3 labs are used to study microbes that can be transmitted through the air and can cause serious disease or death if untreated. These diseases are treatable with existing vaccines or treatments. Researchers perform lab work in a gas-tight room within boxes that filter the air. Other safety features include clothing decontamination, sealed windows and rooms, and specialized ventilation systems with HEPA filters. Most facilities and Universities in the US with infectious disease research programs have BSL-3 labs, and many hospitals have BSL-3 areas for isolating patients with highly contagious diseases. BSL-3 labs work with pathogens such as anthrax and plague. Access to BSL-3 labs is tightly controlled.
• BSL-4 labs are used to study microbes that can cause serious illness or death and for which no vaccine or therapy is commonly available. Lab personnel are required to wear full-body sealed suits with their own air supply and to shower when exiting the facility. The labs incorporate all BSL 3 features and occupy safe, isolated zones within a larger building. Those zones are at negative atmospheric pressure to keep all air within the lab and filtered. BSL-4 labs work with pathogens such as ebola and other hemorrhagic fevers. Access to BSL-4 labs is tightly controlled, physically and procedurally.