NYC-WTC_000230955

NYC 9/11 Public Portal Document

2.0 Scope of Work 24 Air Sampling Procedures

ALC’s licensed teclmiciati collected air samples using TEM Methodology. The technician collected, five (5) air samples rliroughout the building in apartments and hallways.

The air samples were collected using high volume air sampling pumps. Once the pumps were in place the ait sanrpling technician recorded the location, time, date, sample numbers, pump number, flow rate, start and stop times and his initials.

The ait cassette was independent of the pump, motor. This is to prevent the vibrations of to motor from affecting the fibers in the cassette. A separate stand or tripod was used to hold to cassette in place. ITie cassette was angled 4.5 degrees downward from the horizontal stand. This is to insure tot no Uibestoa will drop into to cassette while sampling.

Using a rotameter, we calibrated each pump to the required flow rate, noting this rate on to sample record. After cahbiating to pumps, to end cap from the cassette was removed; to pump was turned on and run for to required amount of lime.

The sampling pumps were checked periodieally to ensure they were stfll operating, to cassettes were still in place, and no one has disturbed to equipment. If at any time to area being sampled was suspected of having high fiber counts, the filter inside tlie cassettes were examined for "overloading”, or an excessive amount of fibers and/or debris on to filter.

When the pie-detcrmined volume of air has been collected, the technician ton calibrated the sampling pump again tO determine to current flow rate. This rate will often be different from to flow rate measured at the bsgianing of to sampling period. That dHTcrence is usually due to the clogging of the filter, thereby adding increased resistance to to flow of air.

Once the pre-determined volume of air has been reached, to time was recorded as well as on the cassette. Before the pump was turned off, the cassette was angled upward and to cap replaced and to end plug. The cassettes were plan ed in sealed containers, labeled with an identifying code and a sample log was kept. The aampl cs were then submitted to to laboratory to be analyzed for asbestos content, A chain of custody record was prepared and accompanied the samples to to laboratory.

24 Asbestos Analysis and Methodology

Each air sample is oross-ieferenced by field designation and lab intamal code to ensure proper, consistent handling through a chahi of custody. Sample preparation tabes place within a HEPA Filter clean bench to avoid any possible contamination. Air sampling was conducted at a level approximating the breathing zone Of persons (tnlieipated to be present in the area during normal operations. Samples collected represent the typical airborne fiber concentration of the area.

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NYC-WTC_000230960