Law Department notice on WTC document preservation, Oct 2001

NYC 9/11 Public Portal Document

Method Flow Rate Sample Train Media 7300 Lead 2 liters per minute 37 mm cellulose ester membrane minimum sample volume to (0.8 micron) Closed Face achieve detection limits 50 liters 7400 Fibers (Asbestos and 2 liters per minute** 25 mm cellulose ester membrane Man Made Vitreous Fibers minimum sample volume to (pore size 0.45 - 1.2 microns) MMVF) achieve detection limits - with conductive cowl. Open face 400 liters 7500 Respirable Silica/ 1.7 liters per minute** 37 mm PVC membrane (pore Calcite/ Gypsum* minimum sample volume to size 5 micron) with 10 mm nylon achieve detection limits - cyclone 400 liters

* This methods requires that a bulk respirable or settled dust sample be submitted with personal breathing zone sample to identify interferences with detection method. **These methods are sensitive to filter over loading. Length of sampling period should not exceed 4 hours. Use multiple sample periods to represent entire shift exposure.

Samples will be collected on individuals performing tasks representative of exposure conditions. Specifically the following tasks will be characterized:

• Common area cleaning; • Non-HEPA vacuuming; and, • Cleaning of areas not previously cleaned.

Sample pumps will be pre- and post sample period calibrated using a sample train in-line between the pump and calibration unit to simulate pressure drop posed by the sample train. Calibrations will be made with a primary calibration device (e.g., film flow calibrator or near frictionless piston).

Sample results will be communicated by the SHSO to employees represented by the sample data within five days of receipt on the WRS Air Sampling Data Acknowledgement Form. This data is forwarded to the WRS H&S Manager for inclusion in the employee’s medical file.

-001 WRS Infrastructure and Environment, Inc. 18

NYC-WTC_000145095