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For a fire to start, three components of the triangle namely: Fuel, Oxygen and Ignition sources need to come together (Figure).

Figure: Components that cause a fire on coming together

There are different types of accidents that can occur in the TB lab. These accidents and actions to be taken are elaborated below:

Tube Breaks or Infectious Spills inside the Biosafety Cabinet (BSC)

The emergency preparedness plan in a tuberculosis (TB) laboratory is a written document that should provide:

• Operational procedures for incidents and accidents while storing or dealing with tubercule bacteria isolates
• Precautions against natural disasters, for example, fire, flood, earthquakes and explosions

Figure: Composition of an Emergency Preparedness Plan

Depending on the procedural risk in the TB lab, the lab is classified into low, moderate and high-risk categories.

Low-risk TB laboratories work on sputum specimens for:

1. Direct Acid-fast Bacilli (AFB) smear microscopy
2. Cartridge-based Nucleic Acid Amplification Test (CBNAAT)/ Truenat

Figure 1: Procedures Conducted in a Low-Risk TB Lab

As part of the biosafety measures in TB labs, there are specific standards that need to be followed for lab equipment.

Key Features of Laboratory Equipment in TB Laboratories

The equipment should be:

Ventilation is an essential biosafety design feature in a TB lab.

Laboratory ventilation has three basic elements: 

1. Ventilation rate  

Amount of outdoor air that flows into the laboratory.

2. Airflow direction 

Overall direction of air flowing through the laboratory should be from functionally clean areas to dirty areas.

3. Airflow pattern 

The basic recommended design features of TB laboratories to ensure appropriate biosafety are:

• Adequate ventilation and directional airflow; 6-12 air exchanges per hour (ACH) is adequate ventilation for TB laboratories.
• Ample space for the safe conduct of laboratory work and for cleaning and maintenance (Figure 1).

Figure 1: Ample and open spacing in an ideal TB lab

The Cartridge-based Nucleic Acid Amplification Test (CBNAAT) files should be archived and saved to a CD or other appropriate external media (preferably an external drive), at least once a month to ensure that no test data are lost.

Archiving tests creates copies of the test data in “gxx” files. 

Importance of Archiving and Back-up 

Archiving allows you to:

1. Back-up data to ensure it will not be lost if the computer breaks down.

Monthly maintenance tasks of the CBNAAT instrument include:

Cleaning of the Cartridge Bay and Plunger Rod

The CBNAAT manufacturer recommends monthly cleaning of the cartridge bay and plunger rod. However, if the sample load is high, this task can be carried out on a weekly basis.

Cleaning of Module PCR Slot (Figure 1)

While using the CBNAAT machine in a laboratory setting, many different causes can lead to an error (indicated on-screen as ‘ERROR’, as in figure 1).

Figure 1: Window showing how to click on “Errors” to learn more about the issue

Error Message Categories

The errors are displayed by the instrument’s software to highlight various technical issues that disrupt the test process. They are grouped into five categories by the software: