E-mails 2003 M. Gilsenan

NYC 9/11 Public Portal Document

7. Place the air handling units and their 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 if needed.

8. If there is an outside air intake, clean the intake louvers by damp wiping. If there is an outside air duct and it is accessible, clean the interior surfaces using HEPA vacuums with brush attachments and wet methods. If access to the outside air duct is limited, clean it using a combination of whips (whips only used in ducts without interior insulation), brushes (use soft brushes if ducts have interior insulation), 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 3 feet per minute). Note that vertical risers may be treated similarly to the procedures identified for exhaust ducts.

9. Clean the air intake louvers and filter racks at the return air sides of the AC/ventilation units by damp wiping.

10. Clean all parts of the A/C or ventilation fan unit exposed to the air stream including thermal coils, the blower assembly and housing, and all other components using HEPA vacuum brush attachments and minimal wet methods. Electric coils and components shall be cleaned using dry methods. When wet cleaning thermal coils, apply manufacturer-approved cleaning solution to the coils using low pressure methods (i.e., airless sprayer, hand operated pump).

11. Clean all supply mains and branch ducts in the direction of air flow, starting from the furthest point from the AFD or vacuum collection device. If the ducts are accessible (typically 6’ or less in length from access point) they may be cleaned using HEPA vacuums with brush attachments and wet methods. If access to the ducts is limited, clean them using a combination of whips (whips only used in ducts without interior insulation), brushes (use soft brushes if ducts have interior insulation), 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 3’S3 feet per minute).

Use isolation/zone pillows as necessary to isolate sections of the system, so that sufficient negative pressure is maintained in each work zone and to prevent re-contamination of cleaned sections.

12. Apply encapsulant to any exposed porous insulation in the AC/ventilation system fan unit or ducts.

13. Protect the floor underneath the supply grilles/diffusers or return air grilles using 6 mil polyethylene sheeting. Remove the polyethylene barriers covering the supply air diffusers/grilles and return grilles, while the duct is still under negative pressure.

14. Remove supply air grilles and diffusers to a central location for cleaning. Clean using Simple Green or a similar environmentally safe product. Use bags if necessary when removing the grilles and/or diffusers to prevent dust or debris from being released. Reinstall supply grilles/diffusers and return air grilles after cleaning.

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