The density of gas phase contaminants may be responsible for several important transport phenomena in porous media. One-dimensional laboratory experiments were conducted to explore the transport of a dense gas (Freon-113) through an air-dry sand. Gas densities were measured and fluxes were estimated during transport through a column filled with oso-flaco sand. Significant differences in density profiles and fluxes were observed for the three primary flow directions (horizontal, vertically upward, and vertically downward) at high source densities. Estimates indicate that pressure gradients of up to 20 Pa/m measured in the first 2.5 cm of the column were possibly due to the nonequimolar diffusion of Freon and air. Simulated Freon densities from numerical models based on the standard Darcy-Fickian transport equation did not compare well against measured density data. Density profiles generated by the model differed from the data by up to 400%. Numerical simulations indicated that slip flow may be significant relative to Darcy advective flow, but the slip phenomenon did not account for the discrepancy between model simulations and data. Further research and equation development will be necessary in order to ascertain why the standard theory does not adequately describe the diffusive and advective transport processes for dense gases.