One of the final stages of asbestos abatement is to have an independent consultant do “clearance testing”. Before clearance testing is performed, the asbestos was identified by a consultant and it was abated by a licensed asbestos abatement contractor. Clearance verifies if the abatement work was properly done and the level of airborne asbestos is acceptable. The vast majority of the time in my experience, clearances have met Environmental Protection Agency (EPA) standards. However, in rare cases the abatement work can be done improperly which can lead to a failure. The question that often comes up is what can be done to rectify this?
Basics of Asbestos Clearances
Clearances are conducted in two phases. The first phase is visually verifying if the abatement was successful. This can range from checking pipe insulation for residue, looking for excessive dust, and seeing if tile and mastic were adequately removed, among many other visual checks. The second phase of clearance is air testing. This process includes setting up high volume air pumps which are calibrated to a specific flow rate. Once the appropriate flow rate is reached, a Phase Contrast Microscopy (PCM) or Transmission Electron Microscopy (TEM) cassette is used. The sample will run to the desired volume. Once the sampling is complete, the samples will be sent out to an accredited laboratory for analysis, or in some cases PCM air samples can be analyzed on site. The clearance criteria for PCM is 0.01 fibers per square centimeter (f/cc) and 70 structures per square millimeter (s/mm2). To learn more about PCM and TEM air sampling reference our previous blog on the topic.
Why Do Asbestos Clearances Fail?
Clearances can fail for two primary reasons, which are visual inspection failure or air samples that do not meet regulatory clearance criteria. Visual inspection failure will occur mostly likely if debris of the remaining material or heavy dust is still present in the containment area. This demonstrates that the area has not been properly cleaned. Another reason a visual inspection can fail is if the material that was to be abated is still present. This can occur if the scope of work is not clear with the abatement contractor or could be due to negligence. Here is a picture of a recent project where the contractor left a large amount of asbestos-containing asbestos. Clearance can also fail with air samples having higher fiber or asbestos counts then the regulated limit. This is caused by contractors not controlling the release of fibers during removal or insufficient HEPA vacuuming and wet wiping.
How Are Clearance Rectified?
Once the clearance has failed, the containment must remain in place with negative air machines running until clearance criteria is met. The process to rectify it will typically consist of HEPA vacuuming and wet wiping surfaces to remove any debris present. If more materials need to be removed, then abatement activity will simply continue. Another component of successful clearance is time to allow the negative air machines to property scrub the air of any excess fibers once all debris and materials are removed and cleaning activity has ended. Encapsulant is sometimes also used during the end stages of abatement. The area must be visually inspected and air sampled until criteria has been met. Because the contractor has already failed once, you may want to consider doing clearances with aggressive air movement and TEM cassettes for a more thorough analysis.
Once an asbestos clearance has failed, it must be rectified in order to return the area back to pre-loss condition. The responsibility for attaining clearance and costs of clearance testing after a failed clearance should be with the abatement contractor. The clearance sampling should be conducted by a third party air sampler, such as Indoor Science, with no financial connection with the abatement contractor.