The current advisory for active soil gas investigations in California requires leak tests to be conducted at eveiy soil gas probe while taking a sample. A leak may allow ambient ak into the sample train thus diluting the soil gas and underestimating the results. Also, the leak check compound itself may have impurities thereby contaminating the sample. The advisoiy suggests leak check compounds and lists potential leak points in the sample train that should be investigated. If a leak has been detected but unable to be resolved, the soil gas probe is decommissioned, and a new soil gas probe is installed, or consultation with agency staff required.
Since the leak check results may draw soil gas data into question, the presence of any leak check compound in the sample is a concern. This paper investigates the response of several leak check compounds at determined leak rates into the soil gas sampling train. The diffusion of leak check compounds through the walls of commonly used tubing for soil gas investigation is also evaluated. Finally, considerations for performing leak checks and interpreting leak check data are presented.