25 October 2004
Figure 3-3. Exhaust hood for low profile work pieces.
Fans. See paragraph 2-4.2 for general fan considerations.
Weather Stack Design and Location. See paragraph 2-4.3.
Air Cleaning Devices. A delagging facility requires multistage filtering,
which consists of a fabric filter collector, prefilters, a mist eliminator, and high efficiency
particulate air (HEPA) filters. Prefilters extend the life of the HEPA filters. Use "bag in,
bag out" styles of HEPA filters, which allow for safe replacement of the filter element
without exposure to asbestos. A mist eliminator before the HEPA filter protects it from
the moisture generated during asbestos removal.
a. Have all collectors deliver the collected asbestos to a common pickup
point to minimize the risk of exposure. Provide a double acting valve at
each collector hopper throat, in accordance with the ACGIH IV Manual,
b. Use a single chamber, shaker type collector to minimize the number
of collection points.
Filter Efficiency. The fabric filter collector requires a minimum efficiency
reporting value (MERV) of not less than 15 in accordance with ASHRAE 52.2, Method