Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

APPENDIX A DEFINITIONS

1. Access Doors: Covers for service openings consisting of pre-fabricated operable or removable entry panels, which are installed in a ventilation system to facilitate inspection and maintenance services.

2. Air Conveyance System, Air Handling System, HVAC System, Ventilation System: The ventilation system is any interior surface of a building's air distribution system for conditioned spaces and/or occupied zones (See definition of air handling system, ASHRAE 62-1989). This includes the entire air distribution system from the points that the air enters the system to the points that air is discharged from the system. The return air grilles, air ducts (except ceiling plenums) to the air handling unit (AHU), the interior surface of the AHU, mixing box, coil compartment, condensate drain pans, humidifiers, and dehumidifiers, supply air ducts, fans, fan housing, fan blades, spray eliminators, turning vanes, filters, filter housings, reheat coils, and supply diffusers are all considered part of the ventilation system.

3. Air Filtration Device (also referred to as Negative Air Machine): An external air moving device which can be temporarily connected to a section or sections of an ventilation system to create negative airflow for cleaning and remediation procedures, employing a minimum of DOP- tested HEPA final filtration if exhausted indoors.

4. Air Washing; For duct cleaning, this term applies to the use of pressurized air, in combination with a Vaccuum Collection Device, for transporting dislodged debris into the vacuum collection equipment.

5. Ceiling Plenum: A non-ducted area between the ceiling over a conditioned building space and the floor above, through which air is transported to a conditioned space fi-om an ventilation system (ceiling supply air plenum), or from a conditioned space to an ventilation system (ceiling return air plenum).

6. Coils: Devices inside the ventilation system, which temper and/or dehumidify the air transported by the ventilation system. These include heat exchangers, with or without extended surfaces, through which either water, ethylene glycol solution, brine, volatile refrigerant, steam, or electricity is circulated for the purpose of total cooling (sensible cooling plus latent cooling) or sensible heating of a forced-circulation air stream (See ASHRAE 33-78 and ARI 410-91).

7. Debris: Any solid materials, including particulate substances, in the ventilation system not intended to be present.

8. DOP Testing: The percentage of removal of 0.3 micrometer particles of dioctylphthalate (DOP) is used to rate high efficiency air filters, those with efficiencies above about 98 percent (See Military Standard 282, U.S. Department of Defense, 1956).

9. Ductwork (Ducts): A system of passageways for distribution and extraction of air (See ASHRAE Terminology ofHeating, Ventilation, Air Conditioning, and Refrigeration, 1991).

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