Biosafety
levels (BSL) refer to the various safeguards used to prevent lab workers
and others from becoming infected with the small samples of microbes
that are being studied. There are four graduated biosafety levels, the
lowest being level 1, for working with low-to no-risk microbes. Biosafety
levels 2, 3 and 4 feature additional graduating safety measures with
the highest level being 4. Biosafety level 4 is used for work with infectious
diseases that pose a higher level of danger to humans or for which there
are no cures.
Below is a summary of the safety measures associated with each biosafety level:
Biosafety
level 1 (BSL1)
These labs are suitable for working with microbes that pose no risk, or a very
limited risk, to lab personnel or the environment. Work is often conducted on
open lab bench tops. No special containment equipment is needed and foot traffic
through the lab is not restricted. However, there are limited safety measures.
For instance, contaminated work surfaces must be decontaminated; and eating and
drinking is not permitted in these labs.
Biosafety
level 2 (BSL2)
These labs are built for work with microbes of moderate risk. Accordingly, more
safety measures are in place. For instance, access to the lab is limited, lab
coats must be worn, and biosafety signage is required at entrances. In addition,
special cabinets that contain and filter the air are used for working with microbes
that can move through the air (aerosols).
Biosafety
level 3 (BSL3)
These labs are used for work with microbes that can cause serious injury or,
in cases of an extreme exposure, death. In addition to the safety measures of
level
2 labs, there are several other safeguards. People younger than 16 are not
allowed in these labs. Lab doors must be kept closed. Windows are sealed. Surgical
gloves and masks, or respirators, are used. The rooms are kept at a lower air
pressure level than surrounding rooms, and the outdoor environment to contain
aerosols. Air in the room also is continuously filtered through HEPA filters
that are able to catch minute particles. These filters are regularly disinfected
and changed.
Biosafety
level 4 (BSL4)
These labs contain the highest level of safety measures to protect those working
inside them and in adjacent areas. The labs are used for work with highly infectious
or dangerous microbes. These labs contain the safety measures of BSL3 labs. In
addition, workers in these labs go through extensive background checks. Access
is very restricted. Entry logs are kept for the labs. Lab workers must wear protective
suits and undergo a disinfectant shower upon leaving. The labs have double-door
airlocks. Special nonbreakable containers are used for working with the microbes.
Materials in the lab are destroyed or decontaminated before leaving.
