Asbestos Contractor/Supervisor Practice Exam

If a contractor passed an air clearance sample using PCM but failed the air clearance when TEM was used, which of the following activities probably contributed the most to the TEM failure?

1. Using improper personal protective equipment

2. Improper sealing of the work area

3. Detail cleaning using wire brushes

4. Failure to enclose the worksite

The correct answer is: Detail cleaning using wire brushes

Detail cleaning using wire brushes is likely the activity that contributed most to the failure of the air clearance when Transmission Electron Microscopy (TEM) was used. TEM is a highly sensitive method that can detect even very small amounts of asbestos fibers. While PCM (Phase Contrast Microscopy) is effective for counting fibers, it typically has a higher threshold for detection compared to the more sensitive TEM. Using wire brushes can release more fibers into the air compared to other cleaning methods due to the abrasive action that disturbs material that may contain asbestos. This action can disturb surface debris and lead to a higher concentration of airborne fibers, which would be picked up by the TEM analysis. Therefore, it stands to reason that this type of cleaning method is particularly disruptive and could be the primary cause of the increased fiber counts in the TEM sample, ultimately resulting in a clearance failure. In contrast, other options like improper sealing of the work area or failure to enclose the worksite may also contribute to fiber release into the environment but would not necessarily impact the air clearance sample as significantly as direct disturbance from cleaning methods. Similarly, the use of improper personal protective equipment (PPE) cannot directly influence the air sample results; however, it does impact worker safety during the process.