Which statement describes the ceiling critical condition?

Which statement describes the ceiling critical condition?

• A. Floor two sheets of 6 mil overlaps walls by 12 inches
• B. Walls two sheets of 4 mil overlaps floor by 12 inches
• C. Ceiling one layer of 4 mil overlaps walls by 12 inches
• D. Walls two sheets of 8 mil overlaps ceiling by 6 inches

Answer: (C)

In this context, the ceiling critical condition means how the containment barrier on the ceiling must be installed to be effective. The ceiling should be covered with a single layer of 4-mil polyethylene, and that sheet should extend over and onto the adjacent walls by 12 inches. This combination creates a continuous, dust-tight boundary at the ceiling–wall junction, reducing the chance that fibers can escape through seams. The other descriptions don’t describe the ceiling barrier correctly: some refer to floor or wall barriers, or specify different thicknesses or overlaps that aren’t the standard for a ceiling critical condition.

In this context, the ceiling critical condition means how the containment barrier on the ceiling must be installed to be effective. The ceiling should be covered with a single layer of 4-mil polyethylene, and that sheet should extend over and onto the adjacent walls by 12 inches. This combination creates a continuous, dust-tight boundary at the ceiling–wall junction, reducing the chance that fibers can escape through seams.

The other descriptions don’t describe the ceiling barrier correctly: some refer to floor or wall barriers, or specify different thicknesses or overlaps that aren’t the standard for a ceiling critical condition.