Receiving report for HVAC consulting services, March-April 2003

NYC 9/11 Public Portal Document

5. Exhaust the vacuum collection system or AFD to the outdoors. If no window is available, a stairwell may be appropriate. Alternately, two vacuum collection systems or AFD's may be connected in series so that a second unit filters the exhaust air from the first. Alternately, the cleaning contractor can have the collection equipment leak tested in-place by an independent third party to ensure that contaminants do not leak through the air cleaning device.

6. Install one layer of 6 mil poly over all bathroom and kitchen exhaust grilles and secure in place with painters tape.

7. Insert and inflate isolation/zone pillows, as necessary to isolate system, so that floors beyond the cleaning scope area outside the work zone, and to maintain sufficient negative pressure in the section of the ventilation system being cleaned.

8. Remove the mushroom or other fan type housing or weather cap assembly from the roof mounting. Disregard this step if the mushroom was removed previously to install the vacuum collection system on the roof.

9. Disassemble and clean the mushroom, other fan type housing or weather cap assembly using HEPA vacuums with brush attachments and wet methods, as necessary to remove dust (any electrical equipment will not be cleaned with wet methods).

10. Clean the main riser using a combination of techniques including whips, brushes, and compressed air (note: compressed air may be used only if the system is sufficiently isolated and vacuum collection equipment is used to maintain a duct velocity of approximately 3000 feet per minute to capture and transport dislodged material). Cleaning of the riser should start at the furthest point from the AFD or collection device. Clean the.riser prior to cleaning the associated branch ducts.

11. Reinstall the mushroom, other fan type housing or weather cap assembly once the riser or top zone is cleaned.

12. For accessible branch ducts (typically 6' or less in length from access point): One by one, place an approximately 6' x 6' drop cloth of 6 mil polyethylene sheeting on the surfaces below each bathroom and kitchen exhaust grille. Check to ensure that the face velocity at the grille opening is 500 feet per minute or greater. Remove and clean each bathroom and kitchen exhaust grille inside the affected apartment. Clean all branch ducts from inside the apartment bathrooms and kitchens, using HEPA vacuums with brush attachments and wet methods. After cleaning, reinstall the bathroom or kitchen exhaust grille and cover again with polyethylene sheeting secured with painter's tape to help maintain negative pressure within the exhaust ventilation system before moving on to the next grille. Roll up the polyethylene sheeting protecting the surfaces below the exhaust vent and place in a 6 mil polyethylene bag for disposal as asbestos-containing waste.

13. For inaccessible branch ducts (typically 6' or greater in length from access point): prior to inserting mechanical cleaning devices into the access point, construct a temporary containment (see General item 2) to contain the access point. Remove and clean the grille. Clean the branch duct using a combination of whips, brushes, and compressed air (note: compressed air may be used only if the system is sufficiently isolated and vacuum collection equipment is used to maintain a duct velocity of approximately 3000 feet per minute).

NYC-WTC 000135780