<P> Biosafety level 4 ( BSL - 4 ) is the highest level of biosafety precautions , and is appropriate for work with agents that could easily be aerosol - transmitted within the laboratory and cause severe to fatal disease in humans for which there are no available vaccines or treatments . BSL - 4 laboratories are generally set up to be either cabinet laboratories or protective - suit laboratories . In cabinet laboratories , all work must be done within a class III biosafety cabinet . Materials leaving the cabinet must be decontaminated by passing through an autoclave or a tank of disinfectant . The cabinets themselves are required to have seamless edges to allow for easy cleaning . Additionally the cabinet and all materials within must be free of sharp edges in order to reduce the risk of damage to the gloves . In a protective - suit laboratory , all work must be done in a class II biosafety cabinet by personnel wearing a positive pressure suit . In order to exit the BSL - 4 laboratory , personnel must pass through a chemical shower for decontamination , then a room for removing the positive - pressure suit , followed by a personal shower . Entry into the BSL - 4 laboratory is restricted to trained and authorized individuals , and all persons entering and exiting the laboratory must be recorded . </P>
which bsl level is for lethal agents for which there are no vaccines or other countermeasures
Biosafety level 4 ( BSL - 4 )