Conflicting Asbestos Clearance Criteria
You are performing post-abatement clearance air monitoring in a school portable being renovated. The contract specifies clearance at 0.01 fibers per cubic centimeter by phase contrast microscopy (PCM). You collect three samples; two read below 0.01 f/cc, and one reads 0.012 f/cc. The abatement contractor says the sample was overloaded and offers to 're-run the count.' The school district's facilities manager wants the portable reopened tomorrow for summer program registration. You also know the material removed was chrysotile pipe insulation, and PCM cannot distinguish asbestos fibers from other fibers.
1. Should you accept the contractor's offer to re-count, and how do you interpret the 0.012 result?
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A re-count of the same filter is a legitimate quality-control step only if it is done blind and documented as a recount - not a way to obtain a preferred number. The 0.012 f/cc result is a valid data point as collected; it exceeds the contractual clearance criterion. Because PCM is non-specific, the result could reflect non-asbestos fibers, but that ambiguity cuts both ways and cannot be resolved by re-counting the same filter. The correct path: document the result as failing the stated criterion, and if the parties want to resolve fiber identity, use transmission electron microscopy on a properly collected sample. Until then, the portable does not meet the contractual clearance standard, and reopening it is a decision the district makes with that fact in hand - not one you paper over.
2. What do you tell the facilities manager who wants the space reopened tomorrow?
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Give the manager the facts clearly and without hedging: one of three samples exceeded the clearance criterion, the criterion is contractual and tied to the abatement specification, and you cannot certify clearance on this data. Explain the options - recleaning and re-sampling, which is the standard remedy and may be completed quickly, or electron microscopy to characterize the fibers if the parties agree the PCM result is likely non-asbestos. Explain the risk in plain terms: occupancy before clearance means children in a space that has not been shown to be clean. Do not make the reopening decision for the district, but do not soften the finding to accommodate the schedule. Put your conclusion in writing the same day so the manager's decision is informed and documented.