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Tedlar bags bleed some of the volatile compounds of interest--in <br /> particular, benzene--at concentrations up to 3 ppb. <br /> The BAAQMD has also stated that volatile compounds in the laboratory <br /> atmosphere may permeate into the Tedlar bags. A supplier's specifica- <br /> tion sheet states a permeability rate for nitrogen of 0.25 cubic <br /> centimeters (0.25 millimeters) per 100 square inches per 24 hours. <br /> Methylene chloride, a common laboratory extraction solvent, is usually <br /> present in the laboratory atmosphere. Methylene chloride is known to <br /> permeate through Teflon seals on water sample vials and, because <br /> Tedlar is teflon containing a small amount of plasticizer, probably <br /> permeates the Tedlar bags. Other volatile compounds, such as benzene, <br /> 1, 1 ,1-trichloroethane, trichloroethylene, and chloroform, may also <br /> permeate the bags during sampling and analysis activities. <br /> 5.1 .6 Recordkeeping and Chain-of-Custody <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 /> for 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 sam- <br /> ples were split and sent to multiple laboratories, a record sheet <br /> PJ9 9390304.00D 5-5 Rev. 0 09/20/88 <br />