Abatement Work Practices and Procedures
This domain tests the methods used to remove or stabilize asbestos without releasing fibers. Questions often target wet methods, glove bags, mini-enclosures, wrap-and-cut, negative pressure, and the prohibition on dry removal.
Core work practices
Removal must use wet methods and amended water (water with a surfactant) to suppress dust. Workers use HEPA vacuums, not dry sweeping or compressed air. Glove bags are used for small pipe and valve removals; mini-enclosures for larger components; wrap-and-cut for pipe sections that can be isolated and sealed. Work generally proceeds from clean areas toward dirty areas and from top to bottom. Visible emissions indicate a failure of controls and require stopping work.
Negative pressure
Containments are kept under negative pressure relative to adjacent spaces, and HEPA air filtration units exhaust filtered air. A common planning target is at least four air changes per hour, though project specifications may require more.
Worked example
A containment is 20 ft × 15 ft × 10 ft = 3,000 ft³. At 4 air changes per hour, required airflow is 3,000 × 4 = 12,000 ft³/hr, or 200 cfm. If a HEPA unit is rated 500 cfm but is derated 50% for filter loading, it provides about 250 cfm. One unit nominally meets the target, but a second unit is often used for redundancy and better mixing.
Traps
Do not dry-sweep, use compressed air, or remove material dry. Do not rely on a HEPA vacuum alone to control a large release. Do not forget to wet material before and during removal. Do not ignore visible dust or failed negative pressure.