Containment Construction, Decontamination, and Critical Barriers
This domain tests engineering controls: how containment is built, how critical barriers isolate the work area, and how the decontamination unit prevents contamination from leaving.
Containment and critical barriers
Critical barriers seal openings, HVAC vents, doors, windows, and other paths between the work area and occupied spaces. Containment surfaces are typically covered with polyethylene; floors and high-traffic areas may need multiple layers. Seams are staggered and sealed. The enclosure is placed under negative pressure, and the pressure differential is monitored. Decontamination units normally have three stages: a clean room, a shower, and an equipment/dirty room, arranged so workers move from dirty to clean without backtracking.
Worked example
A 3,000 ft³ containment uses two HEPA units rated 500 cfm each. Total airflow is 1,000 cfm; air changes per hour = (1,000 × 60) / 3,000 = 20 ACH. This is well above a 4-ACH planning target. However, airflow alone is not enough: the enclosure must still hold negative pressure, and the decon unit must be sealed and maintained under negative pressure relative to the clean side.
Traps
Do not leave HVAC openings unsealed. Do not build a decon unit that allows dirty air to pass through the clean room. Do not assume one layer of polyethylene is always sufficient. Do not forget the shower or the equipment room. Do not enter through the clean room without the proper sequence.