This document discusses biosafety levels (BSLs) for working with potentially hazardous microbes in a laboratory setting. It explains that there are four BSLs, with each level building upon the previous level's safety controls and containment measures. BSL-1 is for microbes that do not typically infect healthy adults, while BSL-4 is for exotic and extremely dangerous microbes like Ebola virus. The document provides details on the standard practices, safety equipment, and facility requirements for each BSL to minimize risk of exposure and environmental contamination from infectious microbes.

1. Laboratory Learning
Series(LLS)
DR.KAVEH HARATIAN, MEDICAL VIROLOGY,PHD
DEPT. OF MICROBIOLOGY AND IMMUNOLOGY
ALBORZ UNIVERSITY OF MEDICAL SCIENCES

2. Recognizing the Biosafety Levels
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3. Introduction
Suppose you are a laboratory microbiologist working with a potentially harmful microbe.
Precautions must be taken in the laboratory to make sure you and others are not infected.
Where in the lab would you complete your work?
What protective equipment and practices would you use?
How would you contain the microbe to limit contamination or accidental infection?
These are just a few of the questions that can be answered through an understanding of
biosafety and the four biosafety levels (BSLs).
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4. Biosafety and biosafety levels
What is Biosafety?
Biosafety is the application of safety precautions that reduce a laboratorian’s risk of exposure to a
potentially infectious microbe and limit contamination of the work environment and, ultimately,
the community.
What are Biosafety Levels (BSLs)?
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
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5. BSLs, continued
The biosafety levels range from BSL-1 to BSL-4. Each biosafety level builds on the controls of
the level before it. Every microbiology laboratory, regardless of biosafety level,
follows standard microbiological practices.
You will learn about each level on the following screens.
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6. BSL 1
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:
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7. BSL 2
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.
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8. BSL 2, continued
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9. BSL 3
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.
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10. BSL 3, continued
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11. BSL 4
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.
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12. BSL 4, continued
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13. Your turn : Exercises
Now that you have learned about the four biosafety levels, it's your turn to identify the
correct BSL in the examples on the following screens.
Select the Next slide to begin.
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14. Exercise No.1
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15. Exercise No.2
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16. Exercise No.3
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17. Exercise No.4
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18. Summary
Congratulations!
You should now be able to recognize characteristics of the four biological safety levels. If you
would like additional information or resources on the topic of biosafety, select the Next icon. To
view other Quick Learn Lessons, visit CDC Learning Connection.
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19. Resources
For more information on biosafety and laboratory practice, review the following web
resources:
Biosafety in Microbiological and Biomedical Laboratories (5th Edition)
Biosafety — Centers for Disease Control and Prevention
Respirator Fact Sheet
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