Boiler Room Pressure Loss and a Failed Clearance
During a summer abatement at a 1965 school, a licensed contractor is removing 200 linear feet of friable pipe insulation and 60 square feet of tank insulation in the boiler room. The enclosure has three HEPA air machines and a manometer that read -0.018 inches of water column at the end of the shift. Overnight one HEPA unit fails; the morning reading is +0.004 inches. The crew enters at 6:30 a.m. without rechecking the manometer because the supervisor is late. A glove bag on a vertical pipe tears, dropping insulation into the bag and onto the floor. At 9 a.m. the project monitor arrives and sees visible dust on the poly and a tear in the glove bag. A clearance sample later reports 0.013 fibers per cubic centimeter by PCM.
1. What immediate actions should the project monitor and supervisor take upon arriving?
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The first priority is to stop the release and protect people, not to finish the shift.
- Stop work and clear the enclosure: The monitor should direct workers to stop, leave the work area through the decontamination unit, and remain out until the enclosure is repaired and negative pressure is restored. The area should be posted and secured.
- Restore containment: The failed HEPA unit must be repaired or replaced. The enclosure should be checked for tears, loose poly, and failed critical barriers. Negative pressure must be re-established and verified with a manometer before re-entry.
- Address the glove bag tear: The torn glove bag is a direct release point. The bag and debris should be wetted and handled as asbestos waste; the pipe section should be re-bagged or enclosed before work resumes.
- Investigate the entry decision: The crew entered without checking pressure after an overnight equipment failure. That is a work-practice failure, not just a mechanical problem.
Because visible dust is present, the monitor should assume contamination has spread beyond the immediate bag area until cleaning and clearance show otherwise.
2. What corrective cleaning and enclosure repairs are required before clearance sampling can be repeated?
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The monitor should require a full enclosure cleanup rather than spot cleaning.
- Wet-clean and HEPA vacuum: All poly surfaces, the floor, the tank, and the pipe area should be HEPA-vacuumed and wet-wiped. Dry sweeping or dry brushing is prohibited because it resuspends fibers.
- Repair the enclosure: Patch or replace torn poly, reseal seams, repair the glove bag or replace it with a new bag, and verify that critical barriers are intact.
- Restore and verify negative pressure: Replace the failed HEPA unit, check airflow, and confirm a sustained negative pressure before any further abatement.
- Clean the decontamination unit: The dirty room, shower, and clean room should be cleaned so workers do not track contamination out.
- Perform a visual inspection: Clearance air sampling should not begin until the monitor finds no visible debris or dust.
Only after these steps should the contractor request a new clearance sample. Re-sampling without cleaning would simply measure the contamination that is still present.
3. Can the 0.013 f/cc result be accepted as clearance? Explain the standard and next steps.
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No. The result is above the usual clearance criterion of less than 0.01 fibers per cubic centimeter by phase contrast microscopy. The 0.013 f/cc result indicates that the cleaning was inadequate or that contamination remains in the enclosure.
The monitor should reject clearance, document the failure, and require the contractor to re-clean the enclosure, re-inspect visually, and re-sample. If repeated PCM results remain elevated, the monitor should consider whether contamination escaped, whether the sampling method is adequate, and whether TEM or additional sampling is needed. The school should not reoccupy the boiler room until acceptable clearance is documented. The monitor should also document the overnight pressure loss, the unauthorized entry, the glove bag tear, and all corrective actions, because those facts affect both worker protection and the integrity of the clearance.