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Section 3.0 Sampling with Canisters <br /> There are two basic modes of canister sampling: grab and integrated. A grab sample is taken over a <br /> short interval (i.e., 1-5 minutes) while an integrated sample is taken over an extended period (e.g., <br /> 0.5-2 hours for a 1 L canister and 0.5-24 hours for a 6 L canister). In both modes the canister vacuum <br /> is used to draw sample into the canister. This is commonly referred to as passive sampling. Active <br /> sampling utilizes a pump to fill the canister. The most common hardware configuration used to take a <br /> grab sample are illustrated in the following figure. A particulate filter is used to prevent particulate <br /> matter from fouling the valve and entering the canister. <br /> 3.1 Considerations for Grab Sampling i Canisters <br /> The following are some considerations for collecting a grab sample in a canister. <br /> • Avoid Leaks in Sampling Train: All fittings on the sampling hardware are 1/4 in. Swagelok. A <br /> 9/16 in. wrench is used to assemble the hardware. It is not necessary to over tighten the fittings; <br /> finger tight plus 1/4 turn with the wrench is adequate. In practice this should be tight enough so <br /> o <br /> 10 <br /> r <br /> F <br /> r Y <br /> s <br /> 2 a_' <br /> 8 <br />