Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

11.1.2 Site Preparation: To minimize possible contamination and damage, the ventilation system/duct cleaning firm shall provide a negative pressure work area containment as necessary during ventilation system remediation.

11.1.2.1 Negative pressure must be maintained by way of an attached external HEPA- filtered air filtration device. The vacuum must provide at least eight (8) air­ changes in the containment per hour.

11.1.2.2 The AHU servicing the area being cleaned must be shut down or zoned-off and remain so during the cleaning process.

11.1.2.3 Only properly trained, authorized individuals may enter the work area while cleaning is being performed.

11.1.3 System Access: Provide necessary access for cleaning and inspection of the ventilation system.

11.1.3.1 Remove and poly bag difiusers if transport to decontamination area will be through non-containment areas. Clean all grilles and diffusers. Thoroughly dry grilles and diffusers prior to re-installing after cleaning.

11.1.3.2 Install service openings as specified in Appendix B in return air handling systems as necessary to facilitate inspection and cleaning procedures. Access points should not exceed fifty (50) foot intervals to accommodate procedures and final inspection, unless otherwise deemed acceptable by the building management or Environmental Cleaning Contractor.

11.1.3.3 The structural integrity of the ductwork shall not be significantly altered by the installation of service openings (See APPENDIX B).

11.1.4 Duct Zoning: Ventilation system/duct cleaning firm will isolate sections of the ventilation system if needed to facilitate cleaning.

11.1.4.1 Prior to cleaning, ventilation system airflow control devices may be repositioned and zoning devices installed in diffusers and ductwork as necessary to facilitate negative airflow from vacuum collection equipment and to avoid contamination from entering the conditioned air spaces.

11.1.4.2 All zoning devices shall be removed and airflow control devices reset to their pre-cleaning positions upon completion of cleaning in the work area they serve.

11.1.4.3 Zoning devices must be disposed of or cleaned free of contaminant debris or other suitable measures employed to prevent cross-contamination prior to reuse in other ventilation system areas.

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NYC-WTC_000145214