Containment, Decontamination, and Engineering Controls
What this domain tests
This domain tests containment design and operation: critical barriers, negative pressure, HEPA air filtration, pressure monitoring, smoke testing, and the three-stage decontamination unit. Questions often give a gauge reading or a smoke-test result and ask whether work may continue.
Core rules and concepts
- Containment typically uses fire-retardant polyethylene sheeting, commonly 6-mil, with sealed seams and floors. Install critical barriers at openings, HVAC vents, doors, windows, and other paths for air or debris.
- Maintain the work area under negative pressure relative to occupied space using HEPA air-filtration units. A common target is at least -0.02 inches of water gauge, or the project specification, with enough air changes to control fibers. Exhaust must be HEPA-filtered and must not recirculate into occupied space.
- Monitor pressure continuously or at defined intervals. Use a smoke or tracer test to find leaks. Keep backup power or standby equipment for critical filtration.
- The decontamination unit has a dirty room, shower, and clean room. Workers HEPA-vacuum or clean gross contamination, remove outer PPE in the dirty room, shower, and dress in the clean room. Do not bypass the shower or move contaminated PPE into the clean room.
- Engineering controls include glovebags, mini-enclosures, local exhaust, and proper containment. Box fans, open windows, and unfiltered exhaust are not engineering controls for asbestos.
Worked example
A containment gauge reads -0.005 inches of water gauge, and a smoke test shows smoke drifting out of a seam. May work continue?
Reasoning: no. The pressure differential is too low, and the smoke test confirms an unfiltered leak path. Stop work, seal the seam, check critical barriers and HEPA unit operation, add filtration capacity if needed, and verify a stable negative pressure at the project target. HEPA-vacuum and clean the affected area, then document the correction before restarting.
Traps that cost marks
- Running the containment under positive pressure.
- Using a box fan or unfiltered exhaust to "ventilate."
- Omitting critical barriers at HVAC vents and doors.
- Skipping the shower or moving contaminated PPE into the clean room.
- Not monitoring pressure or not responding to a failed smoke test.
- Recirculating HEPA-filtered air into occupied space without approval.