Containment Construction and Engineering Controls
Domain focus
The exam tests containment construction and engineering controls: critical barriers, negative pressure, HEPA filtration, and decontamination.
Core rules
- Use fire-retardant plastic, often 6 mil, on walls, floors, and openings. Seal seams, penetrations, and HVAC vents. Critical barriers separate the regulated area from occupied space.
- Maintain the enclosure under negative pressure relative to surrounding areas. Exhaust through HEPA filters to the outside, away from air intakes. Do not recirculate air.
- Use a decontamination unit with clean room, shower, and dirty room; larger projects may use a four-stage decon. The dirty room must be under containment pressure.
- Provide lighting, signage, and safe access. Use wet methods, HEPA vacuums, and local exhaust such as glove bags where practical.
- Monitor pressure with a manometer and inspect plastic daily.
Worked example
A containment measures 40 ft x 20 ft x 10 ft = 8,000 cubic feet. At 4 air changes per hour, airflow must be at least 32,000 cubic feet per hour. A 1,000-cfm HEPA unit moves about 60,000 cubic feet per hour, so it has nominal capacity, but ducting, filter loading, and makeup air can reduce performance. Verify negative pressure and seal leaks rather than assuming the rating is enough.
Traps
Positive pressure spreads fibers. Recirculating HEPA air into the building is not acceptable. One layer of plastic and taped seams fail inspection. A decon unit not under negative pressure can contaminate clean areas.