Addendum #2 on bulk dust sampling procedures for WTC project,

NYC 9/11 Public Portal Document

a. The monitoring contractor shall schedule and oversee the cleaning of HVAC systems. b. The Monitoring Contractor shall inspect HVAC systems or portions thereof cleaned to verji^ ckmlines& If visible dust or other contaminants are evident through visual TnspectionT^testiiTg^en the Monitoring Contractor will direct the HVAC cleaning contractor toi'cieantnose portions of the system where dust or other contaminants are present and reinspect. c. HVAC cleaning, and cleanliness inspections shall be conducted in accordance with the National Air Duct Cleaners Association (NADCA) General Specification for the Cleaning of Commercial Heating, Ventilating and Air Conditioning Systems and the NADCA Assessment, Cleaning and Restoration Standard (ACR 2002).

12. Sampling of residences and common spaces where cleaning has not been requested a. Based on consultation with resident, aggressive or modified aggressive air sampling will be conducted. i. Before beginning aggressive air sampling, a 1 horsepower electric leafblower shall be used to direct exhaust air against walls, ceilings, floors and other surfaces. This shall continue for at least five minutes per 1,000 square feet of floor. When directing the exhaust, caution shall be taken to minimize disturbance and potential damage to furnishings and personal belongings ii. Residents shall not be present in their residence during aggressive air sampling activities. iii. Personal protective equipment including disposable clothing, gloves, and respirators shall be worn during aggressive air sampling activities. iv. HVAC systems shall be shut down or isolated locally during aggressive air sampling. V. Room and window air conditioners shall not be operated during aggressive air sampling. vi. Leaf blowers shall not be employed for modified aggressive air sampling. vii. All other procedures are identical for aggressive and modified aggressive air sampling, unless otherwise noted. b. At least one 20-inch fan shall be placed in the center of each room sampled. One fan per 10,000 cubic feet of room space shall be used. The fans shall be operated on slow speed and pointed toward the ceiling. The fans shall run for at least 15 minutes prior to the start of sampling. The fans shall operate continuously throughout sampling and shall not be turned off until sampling is completed. c. For studio apartments 3 air samples shall be collected. For 1-bedroom apartments and above, 5 air samples shall be collected. Sampling equipment shall be placed in living areas and away from obstructions. The sampling cassette must be placed on a tripod, not taped to existing surface and should be directed downward at a 45 degree angle. d. Common spaces will be sampled without the use of forced air devices (fans, leaf blowers etc). For small spaces, less than 160 square feet, 3 samples will be collected. For large spaces greater than 160 square feet and less than 25,000 square

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NYC-WTC_000140391