Integrated measurements of radon concentrations within the ground but close to the surface are being used extensively in search for premonitory signals from earthquakes and in exploration for uranium. We present a description of the different components of the radon signals that may be present and describe methods for separating them. We also show quantitatively what signals the different radon-integrating devices are sensitive to, how readings in a given geometry can be related to actual concentrations in the soil gas under conditons of diffusional equilibrium, and what some of the effects of water in soil are. This knowledge allows the magnitude of the local contributions to be measured, so that distant signals can be recognized as departures from these values. The importance of recognizing where upward transport of soil gas occurs is emphasized.