Biological safety levels (BSLs) are prescribed by the CDC (Centers for Disease Control and Prevention) to inhibit contamination of a work environment and ensure worker safety by outlining operating procedures and atmospheric controls.

There are four levels of infectious-agent exposure, each designated to abide by a specific set of control designs and protocol.  To determine the safety control level, labs must consider several factors, and today we are going to focus on the difference between Level 1 and Level 2.

In addition to specifying guidelines for the type of work that is classified under each Biosafety Level, the CDC also has guidelines for the types of precautions and protections needed to mitigate injury resulting from exposure to pathogens.  Creating a secure working environment is a critical goal of the CDC and individual employers.

Biosafety Level 1 is specified as work with well-characterized agents that are known NOT to cause disease in healthy, non-immunocompromised adults.  Special containment practices and devices are generally not required, but institutional laboratory practices must be implemented to reduce risk to lab personnel.

  • LAB TYPES: Standard teaching and researching laboratories.
  • LAB PRACTICES REQUIRED: Standard good laboratory practices, such as use of personal protective equipment (PPE), hand washing and decontamination of work surfaces.
  • SAFETY EQUIPMENT REQUIRED: biological safety cabinets (BSCs) are NOT required and most procedures are performed on an open bench. Special engineering controls, such as fume hoods and cabinets may be used to minimize exposure to chemical or sample spills.


Biosafety Level 2 is specified as work that poses moderate hazards to personnel and the environment. Research or diagnostic activities that are administered with pathogenic bacteria, such as Staphylococcus aureus or Salmonella, fall into this category. This Biosafety Level builds upon Biosafety Level 1; all of the precautions and practices spelled-out in Biosafety Level 1 must be followed in addition to those found in Biosafety Level 2. 

  • LAB TYPES: Primary healthcare diagnostic and research laboratories.
  • LAB PRACTICES REQUIRED: PPE, restricted access to laboratory areas, use of primary engineering controls (PECs) such as biosafety cabinets and glove boxes to reduce the risk of aerosolized exposure to pathogens.
  • SAFETY EQUIPMENT REQUIRED: BSCs are required as a PEC, and research or diagnostic activities must be performed within these devices. In addition, special engineering controls, such as fume hoods and cabinets may be used to minimize exposure to non-pathogenic substances.

Biosafety Level (BSL) operational recommendations are developed to both protect lab personnel and give meaning to their important research. Without these precautions, work would be dangerous, inefficient and more time consuming. 

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