The U.S. Environmental Protection Agency evaluated available pollution reduction capabilities of vapor degreasers fitted with add-on control systems and supplied by greaser manufacturers. The principal objectives of this project were to develop and implement an experimental program for assessing solvent loss from degreasing systems of various designs, and to report the test conditions, procedures, results, and conclusions in a form usable by air pollution agencies and industry. Tests were performed from October 1978 to June 1980 to evaluate the effects of different variables on the rate of solvent loss from degreasers. The variables tested include the following degreaser control options and operating conditions: freeboard ratio, load cross-sectional area, refrigerated freeboard chiller, hoist speed, lip exhaust, crosscurrent air velocity, degreaser size, solvent type, and automatic cover. Various relationships between the test variables are presented in the report. The factor most likely to ensure long periods of operation with minimum solvent loss, regardless of the mix of control options, is installation in an area where crosscurrent velocity can be minimized.