Containment Deficiencies in an Occupied Basement
A three-person crew is removing 240 linear feet of friable pipe insulation from the basement of an occupied 40-unit apartment building. The contractor builds a containment of 4-mil polyethylene, taping it to the ceiling and floor. A negative air machine with a HEPA filter exhausts into the common hallway because the only exterior window is painted shut. Workers enter through a single flap cut in the poly; there is no decontamination unit. At lunch, the three workers sit at a folding table inside the containment and eat sandwiches. Debris is picked up with a household shop vacuum. No air monitoring is performed. The building maintenance man lifts the flap to read the water meter. The contractor tells the owner the job will be finished in two days and asks whether clearance is needed before tenants use the basement laundry.
1. Identify the work-practice deficiencies in this setup and explain why each matters.
Read the worked answer
Deficiencies include: 4-mil poly is too thin for a regulated containment; 6-mil fire-retardant poly is the usual minimum. The negative air machine must exhaust outdoors, away from doors, windows, and air intakes - not into the common hallway, which spreads fibers and defeats the pressure differential. There is no decontamination unit; workers need a clean/dirty decon with a shower or at least a three-stage decon, and a single flap is not a decon. Eating inside containment is prohibited. A household shop vacuum is not HEPA and will aerosolize fibers; use a HEPA vacuum. The maintenance man entering without PPE breaches the containment. No air monitoring means no verification.
2. Describe the corrections the contractor must make before work continues.
Read the worked answer
Correct by rebuilding the containment with 6-mil poly, sealing penetrations, and duplicating the flap into a proper decon. Route the negative air exhaust to the exterior, verify it is not near an intake, and maintain negative pressure with a manometer or smoke test. Provide HEPA vacuum, wet methods, and labeled waste bags. Prohibit eating, drinking, and smoking inside; provide a clean break area. Only trained, licensed, PPE-equipped workers enter. The maintenance man should read the meter before containment or after clearance, or be equipped and trained if entry is unavoidable.
3. Is clearance required before the laundry reopens? What does a proper clearance involve?
Read the worked answer
Clearance is required before the basement laundry is reopened. The contractor should perform a visual inspection to confirm no visible debris or dust, then air sampling by a licensed air-monitoring specialist or consultant independent of the abatement contractor, using PCM or TEM as specified. Maine's clearance criterion is typically 0.01 fibers per cubic centimeter or less inside the containment, with careful sample placement and aggressive sampling. If the result exceeds the criterion, reclean and retest. The owner should not accept the contractor's word that “it looks clean.”