The work presented in this report covers several different modelling and experimental studies into the flow of gases in soil, and forms part of an investigation into how to protect buildings against soil gases. There are three parts: flow due to natural driving forces, high pressure flows, and time dependent effects. For each part, a combination of modelling techniques has been applied to the problems considered and a number of experiments analysed. The modelling techniques used vary from simple analytical models through more advanced analytical techniques to numerical solutions. Some of these develop directly from the work of others, but many are new to the soil-gas field. 272 pages.