Containment Construction and Worker Decontamination
Containment Basics
Containment isolates the work area and prevents fiber release. Candidates must know the components: critical barriers (sealing openings and surfaces), polyethylene sheeting on floors and walls, negative air pressure maintained by HEPA-filtered negative air machines (NAMs), and warning signs at entrances. Negative pressure must be verified (e.g., with a manometer or smoke test) and maintained throughout the job.
Decontamination Systems
A three-stage decontamination unit - clean room, shower, and equipment/dirty room - is standard for larger jobs. Workers move dirty-to-clean: remove contaminated clothing in the dirty room, shower, and dress in the clean room. Equipment passes through a decontamination enclosure or is cleaned before removal. Waste exits through a separate route or bag-out procedure.
Traps to Watch
Frequent traps: (1) assuming positive pressure is acceptable (it is not); (2) confusing the order of rooms in the decon unit; (3) forgetting that the shower is required, not optional; (4) assuming containment can be removed before clearance; (5) forgetting critical barriers before demolition. Also watch for questions about airlock design and about keeping the containment under continuous negative pressure.
Rule of Thumb
Remember "dirty to clean, never back": workers and equipment move in one direction only, and negative pressure always pulls air into the containment.
Worked Example
A worker finishes removal and needs to leave. The correct sequence is: leave the work area into the dirty room, remove contaminated PPE and bag it, shower, then dress in the clean room - never exit directly to the clean room.