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permeate into the Tedlar bags. A supplier's specification sheet <br />states a permeability rate for nitrogen of 0.25 cubic centimeters <br />(0.25 millimeters) per 100 square inches per 24 hours. Methylene <br />chloride, a common laboratory extraction solvent, is usually present <br />in the laboratory atmosphere. Methylene chloride is known to permeate <br />through Teflon seals on water sample vials. Because Tedlar is Teflon <br />containing a small amount of plasticizer, methylene chloride probably <br />permeates into the Tedlar bags. Other volatile compounds, such as <br />benzene and 1,1,1 -trichloroethane, may also permeate into the bags <br />during sampling and analysis activities. <br />• �� • �,��• f•.••. 1.: 1 • •• <br />To ensure data quality, records of all activities that could affect <br />the integrity of a sample were kept. Operation records for the wind <br />utility system and a flow rate curve chart were maintained with the <br />sampler at all times. Sampling records containing date, time, flow <br />rate, location, and comments at sampling start and finish were kept <br />with each sample bag. <br />Chain -of -custody records for each sample were initiated at the time of <br />sampling and contain the following information: <br />• Sample identification number <br />• Date and time of sampling <br />• Type of container <br />• Name of sampler(s) <br />Custody transfers were recorded for each sample; for example, if <br />samples were split and sent to multiple laboratories, a record sheet <br />accompanied each sample. To minimize sampling exposure and potential <br />loss of sample integrity, the number of custodians in the chain of <br />possession was kept to a minimum. Appendix I contains the chain -of - <br />custody documents. <br />PJ9 9390405.00D 5-5 Rev. 0 09/07/88 <br />EM(on Associates <br />