NYC-WTC_000232952

NYC 9/11 Public Portal Document

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(including no paints or glues).

The ambient and personnel air sampling levels set by OSHA need to be below the permissible exposure limit (PEL) of 50 micrograms per cubic meter (ug/m®). If workers are exposed to levels above this limit, certain medical surveillance monitoring, as well as appropriate engineering controls and personnel protective equipment (PRE) are required. Several samples were above the PEL during this project.

Ambient air sampling was conducted in accordance with OSHA recommended guidelines. A personal low volume air pump was placed (n the breathing zone (4-6 feet) and the air was collected onto a 0,8 micron , 37 millimeter cassette. The cassettes were sent to a laboratory for analysis.

Asbestos Air Sampling

Air sample collection and anaiyeis was conducted throughout the abatement project. The purpose was to document the effectiveness of the contractor’s efforts at confining asbestos to the work zone. The program included air sampling and analysis by PCM (National Institute for Occupational Safety and Health (NIOSH) Method 7400],

NIOSH Method 7400 involves ths analysis of all airborne part'culate contaminants captured on a filter medium utilizing vacuum pumps. Sampling cassettes were pre and post calibrated for flow rate in the field utilizing hand held rotometers, which in turn are calibrated against a primary standard in the laboratory. Air samples are then transmitted to the laboratory with a Chain of Custody where, after preparation, they are examined under PCM. Criteria specified for fiber counting is fiber length, length to width ratio, and morphological characteristics.

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Received Time Sep.24. 4:21PM

CITY_21MC100_011835486

NYC-WTC_000232957