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detected at a level of 5,000 ppmv or more,obtain fixed and biogenic gas valves or the equivalent; (e.g.,oxygen,carbon dioxide,methane,and ethylene)data by using a Thermal-Conductivity Detector(TCD)or a hand-held instrument.The RL b. 100-mL gas-tight syringe fitted with an inert valve and wrapped in for oxygen and carbon dioxide should be one percent or less. aluminum foil; E. Pressure Reading: Record pressure readings of each sampling tube c. Gas-tight glass bulb wrapped in aluminum foil;or system in the field logs and report along with the methane concentration to determine if the area is pressurized d. Glass-lined or silicon coated SUMMA'S canister. F. Special GC Requirements:The GC method requires calibration curves D. Precautions for analytes such as methane since it is not a normal target analyte for such an analytical method. a. Hydrogen sulfide is extremely unstable in the presence of oxygen and moisture;therefore,avoid contact of hydrogen sulfide samples with G. Special Hand-Held Instruments Requirements:Hand-held instruments oxygen and moisture. should be calibrated in accordance with the manufacture's instructions. When a hand-held instrument is used to analyze methane samples, b. Due to the high reactivity of hydrogen sulfide gas,avoid contact of confirm at least 10 percent of all positive methane samples(e.g.,more hydrogen sulfide samples with metallic or other non-passive surfaces than 5,000 ppmv),rounded to the nearest whole number,by another during sample collection,storage,and analysis. hand-held instrument(different unit or brand)or by a GC method. c. Care must be taken so that GC components do not react with the 2. Hydrogen Sulfide Sampling Program:Hydrogen sulfide may be analyzed sample. Typically glass-lined injection ports and Teflon"tube packed by a GC using the South Coast Air Quality Management District(SCAQMD) columns are used to avoid loss of hydrogen sulfide due to reaction with Method 307-91 or EPA Method 16,or by an appropriate hand-held instrument active surfaces. (e.g.,LTX-310 calibrated for hydrogen sulfide,Jerome 631-X or Drager TM tubes). 4.0 Analytical Result Reporting: A. Reporting Limit The RL should be equal to or less than 0.5 ppmv or be Consult Appendix H for reporting format and parameters. sensitive enough to allow for a modeled ambient air concentration(at least one microgram per cubic meter)at the soil surface. B. Holding Time:Hydrogen sulfide samples should be extracted directly into a hand-held analyzer within 30 minutes of collection to minimize the risk of Nlz , q losing the hydrogen sulfide due to reaction with active surfaces. If a hand- ' " held instrument is not used,hydrogen sulfide samples should be analyzed Z V ' as below: a. Within 30 minutes of collection,using the GC procedures;or b. Within 24 hours of collection,if a surrogate is added to the samples or > 100 percent duplicate samples are collected. C. Sample Containers:The following sample containers are recommended for hydrogen sulfide: a. Minimum one(1)liter black Tedlaro bag fitted with polypropylene 12/10/2009 -43- 12/10/2009 44-