Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

Air Handling Unit

1. Ensure that the air handling unit motor is locked out and is electrically isolated, and place the air handling unit and its components under containment prior to beginning work. A temporary Zip-wall containment of 6-mil, fire retardant polyethylene sheeting extending from the floor to the ceiling deck, and maintained under negative pressure using a HEPA- filtered air filtration device is sufficient. The footprint of the containment should be large enough to accommodate a ladder or scaffolding. Note that WRS Infrastructure and Environment, Inc. may construct the containment prior to the start of ventilation system cleaning. In addition, WRS Infrastructure and Environment, Inc. shall install a service opening to facilitate cleaning of interior components. The access panel shall be installed in the supply air duct between the blower and the reheat coil. 2. Clean the filter racks at the return air side of the unit by damp wiping. 3. Prior to cleaning, place polyethylene sheeting underneath the coils. Wet clean the upstream and downstream sides of cooling coils. Apply manufacturer-approved cleaning solution to the coils using low pressure methods (i.e., airless sprayer, hand operated pump). 4. Clean the blower assembly and blower housing in place. The blower assembly and blower housing shall be cleaned by a combination of hand vacuuming, damp wiping and air washing. As required in this document, air washing shall only be performed after a vacuum collection device has been installed. 5. HEPA vacuum remaining interior surfaces and components (e g., condenser equipment and compartment, controls, outside air vent to condenser compartment) to remove ail visible debris. No encapsulant materials may be used inside the condenser compartment. 6. Perform a final cleaning by wet-wiping and/or HEPA vacuuming methods of the interior work area containment surfaces, ladders, equipment etc. prior to final visual inspection and wipe sampling.

Reheat Coils

1. Clean the electric reheat coil (located inside the supply air duct) by dry vacuuming or air washing. No liquids may come into contact with the electric reheat coil.

Supply Air Ducts and Terminal Difiusers

1. Remove all terminal diffusers into 6-mil polyethylene bags and proceed to the enclosure constructed for cleaning of the air handling unit. Terminal diffusers shall be wet-cleaned. The diffusers should be sprayed with Simple Green or a similar environmentally safe degreaser and hand washed as needed to remove adhered materials. 2. Seal the diffuser openings using 6-mil polyethylene sheeting to be secured with duct tape. 3. Install a vacuum collection device at the terminal end of the duct section to be cleaned. If the entire duct is not cleaned as one unit, then isolate the section of the duct to be cleaned using a zoning device. 4. The supply air duct shall be cleaned using a pressurized air/mechanical brush system in combination with a vacuum collection device. The direction of cleaning shall be from the air handler toward the terminal end of the duct. (It is permissible to use a mechanical brush followed by application of pressurized air in lieu of combination style equipment.) The 13

NYC-WTC_000145217