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TO E RO E K SOP No.021,REV.1 <br /> „ SOIL GAS SAMPLING METHODS <br /> ASSOCIATES,INC. <br /> PAGE 9 <br /> Summa canisters are expensive and, therefore, are not cost effective when conducting on-site <br /> analysis. Samples collected in canisters and sorbent tubes are shipped off site for analysis, with <br /> the advantage of excellent assurance of sample integrity. Sorbent tubes should be kept cold. <br /> 3.0 CAUTIONS <br /> Both Tedlar®bags and syringes are transparent to light, and many volatile compounds are subject <br /> to degradation in sunlight. Because of this, samples in Tedlar® bags should be stored in a dark <br /> place, such as a cooler, and analyzed as quickly as possible. Syringes should be covered and <br /> wrapped in aluminum foil after collection to minimize exposure to sunlight. In general, samples <br /> collected in Tedlar® bags should be analyzed within 24 hours after collection, at a maximum. <br /> Syringe samples should be analyzed immediately. This will ensure sample integrity and minimize <br /> contaminant loss by degradation processes or absorption onto surfaces. Soil gas samples should <br /> not be subjected to changes in ambient pressure. Samples to be analyzed off site should not be <br /> shipped by air. If condensation is observed in the sample container,the sample should be discarded <br /> and a new sample collected <br /> Seemingly safe sites or situations may still present life-threatening conditions. Even the best <br /> monitoring equipment cannot replace astute observation and common sense. Be alert and aware <br /> of surroundings and conditions at all times. <br />