1.1 Risk assessment for tb laboratories: what is it?

The four-tier classification system of biosafety levels (1–4) described in WHO’s Laboratory biosafety manual² provides broad guidance on basic concepts of biosafety for the development of national and international codes of practice. The challenge for managers of TB programmes and staff at laboratories, particularly in resource-limited settings, has been to interpret the generic risk-group assignments and biosafety levels into specific precautions relevant to a country’s activities.

Definitions of terms

Aerosol-generating procedure

High-risk procedures that may increase the potential for generating droplet nuclei as a result of the mechanical force of the procedure(for example, pipetting, vortexing, centrifuging or mixing).

Airborne transmission

The transmission of disease caused by dissemination of droplet nuclei that remain infectious when suspended in air.

8.3 Spill clean-up kit

The laboratory manager is responsible for maintaining spill response kits. Two spill response kits should be prepared: one placed outside the containment laboratory and one placed inside the laboratory. The kits should include the items listed below.

Spill response kit:

8.2.3 Breakage of tubes inside sealed buckets (safety cups)

Always use sealed centrifuge buckets, and load and unload them in a BSC. If breakage occurs during centrifuging, broken tubes must be discarded in a puncture-resistant container and disposed of immediately.

Decontaminate centrifuge buckets by soaking them in a suitable disinfectant. Do not use bleach to disinfect metal parts because it causes corrosion. Alternatively, buckets may be decontaminated by autoclaving.

8.2.2 Infectious spills (contained within a biological safety cabinet)

When a spill of infectious material occurs within a BSC, a clean-up procedure should begin immediately, and the cabinet should continue to operate.

1. Place absorbent tissue over the spill area, and apply disinfectant solution liberally.

2. If the walls of the BSC have been splashed, clean with a layer of absorbent paper towel liberally soaked in disinfectant solution.

3. Leave affected areas covered with disinfectant for 30 minutes to 1 hour.

4. Carefully collect contaminated sharps material, and place in a puncture-resistant container for disposal.