A model developed by Dr. Parker C. Reist to predict the build-up and decay rates of vapor concentrations following a chemical spill and clean-up was tested. The chemicals tested were: acetone, butyl acetate, ethyl acetate, hexane, methylene chloride, methyl ethyl ketone, and toluene. The evaporation rates of these chemicals were determined both by prediction, using a model developed by I. Kawamura and D. Mackay, and empirically and these rates were used in the Reist model. Chamber experiments were done to measure actual build-up and decay of vapor concentrations for simulated spills and simulated clean-up. The chamber experimental results were compared to the model's predicted results. The Reist model, used with the Kawamura-Mackay predicted evaporation rate, can be useful in estimating equilibrium concentration and the time required to reach the equilibrium concentration.