114 LIBERTY 2 OF 2

NYC 9/11 Public Portal Document

December 17, 2002 114 LIBERTY STREET REMOVAL OF DUST, DEBRIS, AND CONTAMINATED MATERIALS

08 PRESSURE DIFFERENTIAL & AIR FILTRATION SYSTEM

PART 1 - GENERAL

1.01 DESCRIPTION OF REQUIREMENTS:

A. Isolate the Work Area from all adjacent areas or systems of the building with a pressure differential that will cause a movement of air from outside to inside at any breach in the physical isolation of the Work Area.

B. Continuously maintain the Work Area at an air pressure that is lower than that in any surrounding space in the building, or at any location in the immediate proximity outside of the building envelope. This pressure differential, when measured across any physical or isolation barrier, must equal or ejceed a static pressure of 0.02 inches of water.

C. Accomplish the pressure differential by exhausting a sufficient number of HEPA filtered fan units from the Work Area. The number of units required will depend on machine characteristics, the seal at barriers, and required air circulation. The number of units will increase with increased make-up air or leaks into the Work Area.

D. In addition to the required pressure differential, ensure that a sufficient amount of filtered air is exhausted from the Work Area to provide a minimum of four (4) air changes per hour.

1.02 MONITORING:

A. Continuously monitor and record the pressure differential between the Work Area and the building outside of the Work Area with a monitoring device incorporating a continuous recorder (e.g. - strip chart).

B Provide monitoring of equipment during periods of no work where containment and negative air units are operational.

C. Contractor shall maintain records of monitoring until directed by the Owner. Records shall be available for review at the Owner’s request.

1.03 SUBMITTALS:

A. Submit design of pressure differential system to Ambient Group, Inc. for review prior to the start of work. Do not begin work until the submittal is returned wth Ambient Group Inc. approval.

PART 2 - PRODUCTS

2.01 HEPA-FILTERED FAN UNITS:

A. Air Filtration Devices shall be equipped with High Efficiency Particulate Air (HEPA) filtration systems and shall be approved by and listed with Underwriter's Laboratory. Air filtration devices shall be "Microtrap" as manufactured by Asbestos Control Technology of Maple Shade, NJ or

35 © AMBIENT GROUP, INC.-2002 PRESSURE DIFFERENTIAL & AIR FILTRATION SYSTEM

NYC-WTC_000155687