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. Section No 6 <br /> Revision No 0 <br /> Date September 5, 1991 <br /> Page 6 of 55 <br /> 200 ml of soil gas at a flow rate between 100 and 200 ml/min. When the total <br /> flow volume has been obtained, a solenoid valve is automatically closed and <br /> the sample collection is complete The mass flow meter delivers sample <br /> volumes between 20 and 5000 standard ml with less than 2 percent error <br /> independent of temperature and vacuum conditions <br /> 6 2.3 Decontamination of Equipment <br /> Prior to each use and reuse, each stainless steel sleeve, sampling <br /> probe, point and bailer are steam cleaned and stored in clean storage areas <br /> on the drive point rigs Care is taken with this equipment to eliminate both <br /> soil-surface and cross-hole contamination Vinyl or latex surgical gloves <br /> are worn during handling and assembly of the sampling apparatus <br /> Adaptors and stainless steel bottles are heated to 120 degrees C using <br /> a convection oven and held for 1 hour at that temperature Carbon packed <br /> desorption cartridges are purged at 400 degrees C with helium for 8 minutes <br /> Cartridge holders are heated and purged at X200 degrees C for 20 minutes <br /> Separate storage areas are provided for used and cleaned equipment No <br /> equipment is reused without cleaning <br /> 6 3 Air Sampling <br /> 6 3 1 General Considerations <br /> Gas samples may be collected from a variety of environments and sources, <br /> each of which require specific sampling techniques <br /> • ■ Ambient Air Samples may be collected at stations near potential <br /> omission sources and located relative to wind direction, land use, <br /> and topography as specified in the sampling and analysis plan <br /> 6-6 <br />