In this simple model, a quantity of DNAPL is added to a sealed beaker containing air and water. The water is assumed to be well-mixed, and the air is assumed to be well-mixed. The air and water, however, are not mixed together. The model simulates the transport of mass across the air-water interface until the system reaches dynamic equilibrium. The kinetics of the transfer are assumed to be controlled by diffusion through boundary layers on either side of the interface. Most of the key input parameters can be specified below. The size of the beaker and the quantities of media are fixed.