Clinical and Laboratory Standards Institute document M29-A4—Protection of Laboratory Workers From Occupationally Acquired Infections; Approved Guideline—Fourth Edition is intended to be a practical tool to aid in the development of an effective biosafety program for laboratory workers. It promotes best laboratory practices to protect workers from exposure to infectious diseases encountered in the clinical laboratory and to minimize the potential transfer of infectious organisms outside of the laboratory. These practices include but are not limited to use of standard precautions, good laboratory practices (eg, disinfection of contaminated work surfaces), safety devices, personal protective equipment, and appropriate decontamination and disposal of biological hazards. It emphasizes that specific policies and procedures, along with appropriate training of personnel on consistent application of laboratory precautions during the performance of work tasks, are essential administrative controls for the prevention of laboratory-acquired infections. Information is provided on safe transport of infectious substances, laboratory equipment hazards, occupational health and incident response, planning for public health emergencies, and best practices for biosafety training and competency assessment. Guidelines for the development of an effective biological risk assessment are also provided.

The entire document was reorganized and updated with the focus on providing those responsible for providing a safe workplace with best practices for designing, implementing, and continuously improving the biosafety program for a clinical laboratory.

• Information on safe practices for the autopsy suite is no longer within the scope of M29. For reference purposes, the text from the previous edition was moved to Appendix A but was not revised. The most current guidelines for autopsy/necropsy and surgical pathology are contained in Guidelines for Safe Work Practices in Human and Animal Medical Diagnostic Laboratories.1

• Information on standard laboratory practices that all clinical laboratories should follow when working with materials that could contain infectious agents, including bloodborne pathogens, was consolidated into a single section. Additional precautions to follow when working with agents known or suspected to cause laboratory-acquired infections (LAIs) are provided.

• Discussion of engineering controls and good housekeeping practices applicable to all clinical laboratories was updated. 

• The section on shipping biohazardous material was updated to reflect current national and international regulations and has been supplemented with guidance on safe transport between laboratory sections as well as between laboratory facilities within a single institution.

• Current information on safe handling of material that might contain proteinaceous infectious particles was added to the section on medical waste management (see Section 12).

• Information on mitigating risks posed by laboratory equipment that may be exposed to biological agents was added, including recommendations for routine cleaning and decontamination. Best practices for preparing equipment for onsite repair and for return to the manufacturer for repair, refurbishing, or disposal were updated.

• The section on incident response to release, exposure, or injury involving potentially infectious materials was updated. Information on best practices for occupational health programs and their role in preventing and treating LAIs was updated. A new section on preparedness for public health emergencies was added.

• The section on biosafety training was extensively rewritten. Additional information was included on design and implementation of a biosafety training program based on recent guidance from the Centers for Disease Control and Prevention and Association of Public Health Laboratories on biosafety laboratory competencies.

This guideline is intended to describe best laboratory practices for the protection of clinical laboratory workers from exposure to infectious pathogens. M29 was revised to guide clinical laboratory directors, managers, and supervisors in developing an effective laboratory-specific biosafety program according to the risks associated within the scope of services offered by the laboratory. The focus of this document is to provide guidance for laboratory management on the integration of appropriate biosafety practices within the overall laboratory safety program.

The implementation of effective administrative controls as described herein is intended to provide the safest possible laboratory workplace where potentially infectious materials are present. This guideline directly addresses issues concerning the biological risks present in clinical laboratories, in hospitals, and in other patient care settings. The same risk mitigation and exposure avoidance practices are also suitable for many other diagnostic laboratory settings, such as physician’s office laboratories; reference laboratories; or local, regional, or state public health laboratories.

Even workers in a clinical veterinary diagnostic laboratory are at risk for exposure to many common and uncommon infectious agents present in their patients’ specimens. Although this document does not specifically address medical or animal research laboratories, information may be applicable to research settings in which specimens containing potentially infectious materials are tested.