The control of emissions from vapor degreasers serves two purposes: 1) it removes the contaminant at the source preventing exposure to workers, and 2) it concentrates the solvent into a smaller volume of air which allows for solvent recovery with considerable savings. Evaluation of performance requires knowledge of capture efficiency. Improved local exhaust system design requires a method to predict capture efficiency before the hood in constructed and tested. A model which can be used to predict capture efficiency for flanged slot hoods exhausting area sources in the presence of a uniform crossdraft has been developed and validated under controlled laboratory conditions. This project proposes to field validate the capture efficiency model and quantify industrial crossdrafts. Capture efficiency of hoods used to exhaust vapor degreasers will be measured during actual use. Crosssdrafts in the vicinity of the degreaser will be measured simultaneously with caplure efficiency. This will allow for comparison of predicted capture efficiency, using the model, with measured crossdraft velocity. Activities involving the degreaser as well as those in the vicinity of the degreaser will be recorded. The activity factors will be correlated with the crossdraft and capture efficiency measurements. The research will lead to 1) An improved method for predicting hood capture efficiency and improved hood design methods; and 2) A better and more systematic evaluation of industrial crossdrafts including the turbulence characterstice of these crosodrafts. Improved hood design methods combined with a better understanding of the characteriatics of industrial crosadrafts will result in improved air quality in plants using vapor degreasers, lower probability of health hazards and mdety hazards associated with air concentrations of halogenated solvents, and the strong possiblilty of lower operating costs if the solvent is recovered from the local exhaust system.
