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The main soil‐gas transport parameters, gas diffusivity and air permeability, and their variations with soil type and air‐filled porosity play a key role in soil‐gas emission problems including volatilization of toxic chemicals at polluted sites and the production and emission of greenhouse gases. Only limited information on soil‐gas transport parameters across the vadose zone is available, especially for soil layers below the root zone. In a series of studies, we developed new data for the soil‐gas transport parameters in different soil profiles and tested existing and new predictive models. In this first study, we measured gas diffusivity at different soil‐water matric potentials on undisturbed soil samples for three lysimeter soil profiles down to 1.4‐m depth and for two field soil profiles down to 5.6‐m depth, representing a total of 22 different soil layers with soil texture ranging from sand to sandy clay loam. Five commonly used …