The dataset contains details of field collection of test soil gas samples with use of Supel Inert Foil gas sampling bags and the results of methane and ethane measurements performed in order to validate a methodology of soil gas sampling and analysis. The dataset is not intended to be used for any site characterisation, sampling sites were chosen based on high probability of occurrence of measureable methane content in soil gas. Furthermore, the data will be used for formal procedure to obtain the methodology accreditation from the Polish Centre for Accreditation (PCA). The dataset might be used as a set of results of the analytical methodology in future field experimental works. However measurement data are related to particular soil types and beside validation/inter-comparison purpose are not reusable. The dataset was created within SECURe project (Subsurface Evaluation of CCS and Unconventional Risks) - https://www.securegeoenergy.eu/. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 764531