What is enclosure in asbestos control terminology?

• A. A physical barrier that isolates ACM from the work area, often used with negative pressure to prevent fiber release.
• B. An engineering control that eliminates all exposure from the start.
• C. A ventilation duct to remove air from the work area.
• D. A scheduled clean-up procedure after completion.

Answer: (A)

Enclosure is about surrounding the asbestos-containing material with a sealed boundary that keeps it separated from the rest of the workspace. This physical barrier creates a contained work zone so fibers can’t drift into surrounding areas. When the enclosure is operated under negative pressure, air flows into the enclosure rather than out, helping to capture any fibers that might be released and directing them to a filtration system. This combination directly limits exposure at the source by containment, which is why it’s considered an effective engineering control.

The idea behind this approach is that you prevent release before it happens, rather than relying on cleanup after fibers have escaped or on ventilation alone to remove them from the room. Other options describe broader ventilation or post-work procedures, or the notion of eliminating exposure entirely, which aren’t as precise as saying the work area is physically sealed off.