[en] Processes affecting transport of volatile species in the shallow soil column have recently been recognized as having a substantial impact on a broad array of real world problems. Investigations of volatile transport have ranged from studies of probable health impacts of radon infiltration into homes to pesticide and volatile organic contaminant mobility in the soil column. The objectives of many of these studies has been the development of numerical models of vapor phase (and solute) transport in shallow soils. An early model, LEACHM, developed by Hutson and Wagenent was recently modified enabling it to describe both solute and vapor phase transport of volatile chemicals in the soil. Subsequent tests of the latter model, named LEACHV, showed that use outside of a very restricted range of soil conditions resulted in large mass balance errors and unreasonable values for soil gas concentrations and vapor flux. The present research was undertaken in an effort to identify and correct the subroutines responsible for the problems and to allow the model to describe vapor phase transport in a much broader range of soil conditions