Clearance Sampling After a Hospital Mechanical Room Abatement
A licensed air sampling professional arrives at 6:30 a.m. to perform final clearance sampling in a hospital basement mechanical room after removal of 300 linear feet of friable pipe insulation. The containment has been visually cleaned; the supervisor says the final visual inspection passed. Two HEPA negative-air machines are running, but the building engineer has already restarted the air-handling unit serving the adjacent pharmacy to 'dry things out.' The outside doors are propped for equipment movement, and it is raining. The air sampling professional plans five PCM samples inside the containment and one outside. Results: four inside samples 0.003-0.006 f/cc; one inside sample 0.012 f/cc; outside 0.002 f/cc. The supervisor asks the professional to 'call it a pass because the average is below 0.01' and says the pharmacy opens at 8 a.m.
1. How should the air sampling professional evaluate the results, and can clearance be granted?
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Clearance should not be granted. The 0.012 f/cc sample exceeds the 0.01 f/cc PCM clearance criterion, and clearance is based on every sample, not an average. The 0.012 result is an outlier that must be investigated: it may reflect incomplete cleaning, disturbed dust from the propped doors, or HVAC activity. The sampling conditions were also compromised because the air handler was restarted and outside doors were open during rain. The professional should document the deviations, fail the clearance, and require re-cleaning and re-sampling under controlled conditions. The supervisor's request to average the results is not acceptable.
2. What should the professional do about the HVAC and doors before re-sampling?
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Before re-sampling, the professional should ensure the containment is intact and the HEPA negative-air machines are running. The building engineer should shut down or isolate the air handler serving the pharmacy unless the project design requires normal HVAC operation for clearance; the outside doors must be closed to stop cross-drafts and moisture. The supervisor should re-clean the containment, including ledges, equipment, and the decon area, then allow the air to settle. The professional should re-sample at the same locations plus any suspect area, and should not re-sample until the conditions match the clearance protocol. The pharmacy opening time is not a reason to skip these steps.
3. What documentation and communication are needed after the failed clearance?
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Document all results, the failed sample, the HVAC and door deviations, and the corrective actions in the clearance report. Notify the supervisor and hospital infection control that clearance failed and the mechanical room remains restricted. Do not issue a clearance report or allow the pharmacy to rely on the 0.012 sample as a pass. If the hospital pressures the professional, explain that the report must be accurate and that a failed clearance is a reportable result to the client. The final report should include the re-sampling results and a clear pass/fail statement.