Biological Safety Manual - Chapter 03: Principles of Biosafety


Biological Safety Manual - Chapter 03: Principles of Biosafety



A fundamental objective of any biosafety program is the containment of potentially harmful biological agents. The term "containment" describes a combination of primary and secondary barriers, facility practices and procedures, and other safety equipment, including personal protective equipment (PPE), for managing the risks associated with handling and storing hazardous biological agents and toxins in a laboratory environment. The purpose of containment is to reduce or eliminate exposure of laboratory workers, other persons, and the outside environment to potentially hazardous agents. The use of vaccines may provide an increased level of personal protection. The risk assessment of the work to be done with a specific agent will determine the appropriate combination of these elements. Final determination on the combination of containment measures required to address the relevant biosafety risk present at a facility should be based on a comprehensive biosafety risk assessment. A comprehensive biosafety risk assessment is a key component of a successful biosafety program and should be part of an all-hazards risk assessment; it should be conducted on a continual basis to address evolving risks within the laboratory environment. Detailed information on the biological risk assessment process is found in Section II of BMBL. Management and leadership, with support from the facility’s biosafety professionals and other health and safety personnel, must perform and review the risk assessment using the best available information. Management and leadership are responsible for assessing the risks and selecting the appropriate combination of risk mitigation measures.


All persons in the institution are responsible for performing their work in a manner that ensures the successful implementation and performance of the safety measures identified in the risk assessment and review.

Table of Contents

  1. Laboratory Practice and Technique
  2. Safety Equipment (Primary Barriers)
  3. Personal Protective Equipment
  4. Facility Design and Construction (Secondary Barriers)
  5. Facility Practices and Procedures
  6. Biosafety Levels
  7. Animal Facilities
  8. Clinical Laboratories
  9. Laboratory Biosecurity
  10. Importation and Interstate Shipment of Certain Biomedical Materials
  11. Select Agents
  12. References

I. Laboratory Practice and Technique

The most important element of containment is strict adherence to standard microbiological practices and techniques. Persons working with infectious agents or potentially infected materials must be aware of potential hazards and must be trained and proficient in the practices and techniques required for handling such material safely. The director or person in charge of the laboratory is responsible for providing or arranging the appropriate training of personnel.

Each laboratory should develop or adopt a biosafety or operations manual that identifies the hazards that will or may be encountered, and that specifies practices and procedures designed to minimize or eliminate exposures to these hazards. Personnel should be advised of special hazards and should be required to read and follow the required practices and procedures. A scientist, trained and knowledgeable in appropriate laboratory techniques, safety procedures, and hazards associated with handling infectious agents must be responsible for the conduct of work with any infectious agents or materials. This individual should consult with biosafety or other health and safety professionals regarding risk assessment.

When standard laboratory practices are not sufficient to control the hazards associated with a particular agent or laboratory procedure, additional measures may be needed. The laboratory director is responsible for selecting additional safety practices, which must be in keeping with the hazards associated with the agent or procedure.

Laboratory personnel, safety practices, and techniques must be supplemented by appropriate facility design and engineering features, safety equipment, and management practices.

II. Safety Equipment (Primary Barriers)

Primary barrier or primary containment is defined as physical containment measure(s) placed directly at the level of the hazard. Safety equipment such as biological safety cabinets (BSCs), enclosed containers, and other biosafety controls are designed to protect personnel, the surrounding community, and the environment from possible exposure to hazardous biological agents and toxins. Primary barriers can function to either provide containment (e.g., BSCs) or direct personal protection from the hazardous biological agents and toxins used.

The BSC is the principal device used to provide containment of infectious splashes or aerosols generated by many microbiological procedures. Three types of BSCs (Class I, II, III) used in microbiological laboratories are described and illustrated in Chapter 9: Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets.

Additional primary containment devices may include sealed containers (e.g., sealed rotors and centrifuge safety cups). These enclosed containers are designed to contain aerosols, droplets, and leakage of hazardous biological agents and toxins that may result during certain activities (e.g., centrifugation). Sealed containers provide containment for transfers between laboratories within a facility, between facilities, and depending upon risk assessment, within a laboratory. Selection of the appropriate primary containment device should be based on the risks identified for those activities likely to produce aerosols, droplets, or result in potential leakage of hazardous biological agents and toxins.

III. Personal Protective Equipment

Personal protective equipment (PPE) helps protect the user’s body from injury from a variety of sources (e.g., physical, electrical, heat, noise, chemical) or potential exposure to biological hazards and airborne particulate matter. PPE includes gloves, coats, gowns, shoe covers, closed-toe laboratory footwear, respirators, face shields, safety glasses, goggles, or ear plugs. PPE is usually used in combination with other biosafety controls (e.g., BSCs, centrifuge safety cups, and small animal caging systems) that contain the hazardous biological agents and toxins, animals, or materials being handled. In situations where a BSC cannot be used, PPE may become the primary barrier between personnel and the hazardous biological agents and toxins. Examples include fieldwork, resource-limited settings, certain animal studies, animal necropsy, and activities relating to operations, maintenance, service, or support of the laboratory facility. Selection of the appropriate PPE should be based on the risks identified for each respective laboratory.

IV. Facility Design and Construction (Secondary Barriers)

The design and construction of the laboratory facility provide a means of secondary containment of hazardous biological agents and toxins. The secondary barriers, together with other biosafety controls, help provide protection of personnel, the surrounding community, and the environment from possible exposure to hazardous biological agents and toxins. When the risk of infection by aerosol or droplet exposure is present, higher levels of secondary containment and multiple primary barriers may be used in combination with other controls to minimize the risk of exposure to personnel and the 26 Biosafety in Microbiological and Biomedical Laboratories unintentional release into the surrounding community or the environment.

Such design features may include, but are not limited to the following:

  • Ventilation strategies to ensure containment of the hazards;
  • Effluent decontamination systems; and
  • Specialized building/suite/laboratory configurations, including:
    • Controlled access zones to support the separation of the laboratory from office and public spaces;
    • Anterooms; and
    • Airlocks.

Design engineers may refer to specific ventilation recommendations as found in the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Laboratory Design Guide.1 Please note that depending on the laboratory facility, design professionals may need to follow or consult with the current versions of additional design recommendations and requirements such as:

  • The National Institutes of Health (NIH) Design Requirements Manual (DRM);
  • World Health Organization (WHO) Laboratory Biosafety Manual;
  • World Organization for Animal Health (OIE) Manual of Diagnostic Tests and Vaccines for Terrestrial Animals; and/or
  • Other similar national or international design reference documents

V. Facility Practices and Procedures

Established facility-specific best practices and procedures are essential to support the implementation and sustainability of a successful biosafety program. Persons working in facilities that handle and store hazardous biological agents and toxins must be able to properly identify all potential hazards and be trained and proficient in necessary safe practices and procedures. Management and leadership are responsible for providing and arranging the appropriate training of all personnel based on their functional roles and responsibilities in support of the biosafety program. Strict adherence to documented laboratory best practices and procedures is an essential element of a robust biosafety program since failure to follow the established procedures could result in an accidental exposure to personnel or unintentional release of hazardous biological agents and toxins into the surrounding community or the environment. All facilities should develop and implement a biosafety program that identifies the hazards and specifies risk mitigation strategies to eliminate or reduce the likelihood of exposures and unintentional releases of hazardous materials. Management and leadership are ultimately responsible for the work conducted within laboratory facilities. When existing safety practices and procedures are not sufficient to minimize the risk(s) associated with a particular hazardous biological agent and/or toxin to an acceptable level, additional risk mitigation measures may be needed. Safety best practices and procedures must be developed and implemented in coordination with other components of the overall biosafety program.

VI. Biosafety Levels

Four BSLs are described in Chapter 4: Laboratory Biosafety Level Criteria, which consist of combinations of of facility design features and safety equipment (primary and secondary barriers), facility practices and procedures, and personal protective equipment. Selection of the appropriate combinations to safely conduct the work should be based upon a comprehensive facility-specific biosafety risk assessment that documents the properties of the biological agents and toxins to be used, potential host characteristics, potential routes of infection, and the laboratory work practices and procedures conducted or anticipated to be used in the future.

It is important to note that the four Biosafety Levels described below are not to be confused and equated with Agent Risk Groups as described in the National Institutes of Health Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules (NIH Guidelines). The Risk Group (RG) of an agent is an important factor to be considered during the biosafety risk assessment process. Biological agents and toxins are assigned to their relevant Risk Groups based on their ability to cause disease in healthy human adults and spread within the community. However, just because a biological agent is listed as a Risk Group 3 agent, it does not mean the activities conducted with that biological agent must occur in a BSL-3 laboratory. The laboratory director is specifically and primarily responsible for assessing the risks and applying the appropriate biosafety levels. The institution's Biological Safety Officer (BSO) and IBC can be of great assistance in performing and reviewing the required risk assessment.

VII. Animal Facilities

Four standard biosafety levels are also described for activities involving infectious disease work with commonly used experimental animals. These four combinations of practices, safety equipment, and facilities are designated Animal Biosafety Levels 1, 2, 3, and 4, and provide increasing levels of protection to personnel and the environment. See Chapter 5: Vertebrate Animal Biosafety Level Criteria for Vivarium Research Facilities for additional details.

One additional biosafety level, designated BSL-3-Agriculture (or BSL 3-Ag) addresses activities involving large or loose-housed animals and/or studies involving agents designated as High Consequence Pathogens by the USDA. BSL 3-Ag laboratories are designed so that the laboratory facility itself acts as a primary barrier to prevent release of infectious agents into the environment. More information on the design and operation of BSL 3-Ag facilities and USDA High Consequence Pathogens is provided in Chapter 12: Agricultural Pathogen Biosafety.

VIII. Clinical Laboratories

Clinical laboratories, especially those in health care facilities, receive clinical specimens with requests for a variety of diagnostic and clinical support services. Typically, the infectious nature of clinical material is unknown, and specimens are often submitted with a broad request for microbiological examination for multiple agents (e.g., sputa submitted for "routine," acid-fast, and fungal cultures). It is the responsibility of the laboratory director to establish standard procedures in the laboratory that realistically address the issue of the infective hazard of clinical specimens.

Clinical laboratories routinely work with unknown specimens and specimens that have the potential to be infected with multiple pathogens; as such, the occupational risks in a clinical laboratory environment differ from those of a research or teaching laboratory. Most public and animal health clinical laboratories use Biosafety Level 2 (BSL-2) facility, engineering, and biosafety practices.5 Clinical diagnostic laboratory personnel may not know what infectious agent or other hazard(s) exist in the specimen they handle and process.

Except in extraordinary circumstances (e.g., suspected hemorrhagic fever), the initial processing of clinical specimens and serological identification of isolates can be done safely at BSL-2, the recommended level for work with bloodborne pathogens such as HBV and HIV. The containment elements described in BSL-2 are consistent with the OSHA standard, "Occupational Exposure to Bloodborne Pathogens."2,3 This requires the use of specific precautions with all clinical specimens of blood or other potentially infectious material (Universal or Standard* Precautions).4,5* Additionally, other recommendations specific for clinical laboratories may be obtained from the Clinical Laboratory Standards Institute (formerly known as the National Committee for Clinical Laboratory Standards).6

* In 1996 the United States Hospital Infection Control Practices Advisory Committee introduced a new set of guidelines, "Standard Precautions," to synthesize the major features of Universal Precautions (blood and body fluid) with Body Substance Isolation Precautions (designed to reduce the risk of transmission of pathogens from moist body substances).6 Standard Precautions apply to:

  1. blood;
  2. all body fluids, secretions, and excretions except sweat, regardless of whether or not they contain visible blood;
  3. non-intact skin; and
  4. mucous membranes.

For additional information on Standard Precautions see reference 6 or the CDC website.

BSL-2 recommendations and OSHA requirements focus on the prevention of percutaneous and mucous membrane exposures to clinical material. Primary barriers such as BSCs (Class I or II) should be used when performing procedures that might cause splashing, spraying, or splattering of droplets. Biological safety cabinets also should be used for the initial processing of clinical specimens when the nature of the test requested or other information suggests the likely presence of an agent readily transmissible by infectious aerosols (e.g., M. tuberculosis), or when the use of a BSC (Class II) is indicated to protect the integrity of the specimen.

The segregation of clinical laboratory functions and limited or restricted access to such areas is the responsibility of the laboratory director. It is also the director's responsibility to establish standard, written procedures that address the potential hazards and the required precautions to be implemented.

IX. Laboratory Biosecurity

In recent years, with the passing of federal legislation regulating the possession, use, and transfer of biological Select Agents and Toxins with high adverse public health and/or agricultural consequences (DHHS, USDA APHIS Select Agents), a much greater emphasis has been placed in the emerging field of biosecurity. Biosecurity and Select Agent issues are covered in detail in detail in Chapters 6 and 14.

While biosafety focuses on the protection of personnel, the surrounding community, and the environment from the unintentional release of hazardous biological agents and toxins, the field of laboratory biosecurity is focused on the prevention of the theft, loss, and misuse of hazardous biological agents and toxins, equipment, and/or valuable information by an individual(s) for malicious use. Nonetheless, a successful containment strategy must incorporate aspects of both biosafety and laboratory biosecurity to adequately address the risks present at the facility.

X. Importation and Interstate Shipment of Certain Biomedical Materials

The importation of etiologic agents and vectors of human diseases is subject to the requirements of the Public Health Service Foreign Quarantine regulations. Companion regulations of the Public Health Service and the Department of Transportation specify packaging, labeling, and shipping requirements for etiologic agents and diagnostic specimens shipped in interstate commerce (See Chapter 11: Transportation of Infectious Substances).

The USDA regulates the importation and interstate shipment of animal pathogens and prohibits the importation, possession, or use of certain exotic animal disease agents which pose a serious disease threat to domestic livestock and poultry (See Chapter 12: Agricultural Pathogen Biosafety).

XI. Select Agents

In recent years, with the passing of federal legislation regulating the possession, use, and transfer of agents with high adverse public health and/or agricultural consequences (DHHS and USDA Select Agents), much greater emphasis has been placed in the emerging field of biosecurity. Biosecurity and Select Agent issues are covered in detail in Chapters 6 and 14 of this document. In contrast with biosafety, a field dedicated to the protection of workers and the environment from exposures to infectious materials, the field of biosecurity prevents loss of valuable research materials and limits access to infectious materials by individuals who would use them for harmful purposes. Nevertheless, adequate containment of biological materials is a fundamental program component for both biosafety and biosecurity.

XII. References

  1. American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASHRAE Laboratory Design Guide: Planning and Operation of Laboratory HVAC Systems. 2nd ed. Atlanta (GA): ASHRAE; 2015.
  2. Bloodborne pathogens, 29 C.F.R. Part 1910.1030 (1992).
  3. Centers for Disease Control and Prevention. Update: universal precautions for prevention of transmission of human immunodeficiency virus, hepatitis B virus, and other bloodborne pathogens in health-care settings. MMWR Morb Mortal Wkly Rep. 1988;37(24):377-82, 387-8.
  4. Garner JS. Guideline for isolation precautions in hospitals. The Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol. 1996;17(1):53–80. Erratum in: Infect Control Hosp Epidemiol. 1996;17(4):214.
  5. CLSI. Protection of Laboratory Workers from Occupationally Acquired Infections: Approved Guideline, Fourth Edition. CLSI document M29-A4. Wayne (PA): Clinical and Laboratory Standards Institute; 2014.
  6. National Committee for Clinical Laboratory Standards. Protection of laboratory workers from occupationally-acquired infections; approved guideline, 3rd ed. Pennsylvania: Clinical and Laboratory Standards Institute; 2005.

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