This part of ISO 11665 describes radon-222 test methods for soil gas using passive and active in-situ sampling at depth comprised between surface and 2 m.This part of ISO 11665 gives general requirements for the sampling techniques, either passive or active and grab or continuous, for in-situ radon-222 activity concentrations measurement in soil gas.The radon-222 activity concentration in the soil can be measured by spot or continuous measurement methods (see ISO 11665-1). In case of spot measurement methods (ISO 11665-6), the soil gas sampling is active only. On the other hand, the continuous methods (ISO 11665-5) are typically associated with passive soil gas sampling.The measurement methods are applicable to all types of soil and are determined according to the end use of the measurement results (phenomenological observation, definition or verification of mitigation techniques, etc.) taking into account the expected level of the radon-222 activity concentration.These measurement methods are applicable to soil gas samples with radon activity concentrations greater than 100 Bq/m3.NOTE This part of ISO 11665 is complementary with ISO 11665-7 for characterization of the radon soil potential.