NYC-WTC_000220454

NYC 9/11 Public Portal Document t'E«-28-2UU2 'I'HU 11:19 AM CLOSINGS 9 ROSE FAX NO. 212 210 6724 P. 37/42

. Hose'Associates JLC Project #01-2089 septemberIB, 2001 Air Sampling Analysts and Procedure 4 Introduction Air sampling is defined as the process of measuring the filter content of a known volume of air enlrained on a filter membrane over a specified period of time. Each sample is cross-referenced by field designation and a JLG lab internal code to ensure proper, consistent handling through a chain of custody, Sample preparation takes place within an HEPA filter clean bench to avoid any poocible ,11 contamination.

Methodology Test procedures for these samples conform to the National Institute of Or.ci ipational Safety and Health (NIOSH) standards.

Air sampling was conducted at a level approximating the breathing zone of persons anticipateri tn be present in the area during normal operations, Samples collected should represent the area's 7 : , typical airt^orne fiber concentration. y All eampico wore cotlected on fully exposed 25 millimeter, 0.8 inlaumetur (pm) cellulose ester membrane air sampling cassettes with conductive cowl.

Anaiytical Procedures ’1 A section of the filter approximating twenty-five percent of the total filter was removed and placed on a pre-cleanfed microscope slide and then exposed to approximately 250 microliter (pl) of acetone vapor, A single 3,0 - 3,5 pl drop of triacetin was applied and a clean #1.5 cover slip was placed upon the filter. The prepared slide was then heated on a slide heater until clarity allowed analysis to he conducted.

< . Analysis was accomplished utilizing a Phase Contrast Microscope in accordance with NIOSH 7400 method, co (in liny lule "A.'’

Pha«e Contrast Microscopy JUG Environmental's laboratory uses an Olympus BH-PC Phase Contrast Microscope, (PCM) equipped with a Walton-Beckett Graticule, Samples were analyzed by first dissolving the filter through a chemical process (described above) and then counting the fiherK with PCM at 400x magniticatipn. Phase contrast increases the light contrast between the object and the background, thus enhancing the microscopiet'e ability to ccc fibers. Normally, 100 microscopic fields or 100 fibers are counted, whichever occurs first,

Analytical Results . The "Summery of Analytical Results" represents the results of the analysis of the samples. The ' ' PCM limit of reliable quantification is less than 0,01 fibers/cubic centimeter (,f/cc) of air, If final tests do not meet these lequirements, the entire work site must be re-cleaned and re-tested.

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NYC-WTC_000220454