The Development and Evaluation of an Emission Factor for a Toluene Parts-Washing Process

Abstract

Field studies were performed to develop and evaluate emission factors for a parts-washing operation using toluene. Ventilation, process, and air concentration data were collected first for the development of an emission factor, then later for evaluation studies. Air concentrations and ventilation rates were used in mass balance models to determine emission rates. The average emission rate was 5.4 grams toluene per minute. The modeled emission rates compared favorably with estimates of toluene use. Emission and process rates were used to develop emission factors. The emission factor for parts washing was 1.6 mg toluene per square centimeter of part washed (r2=0.41, p <0.05). To evaluate this emission factor, process data and ventilation measurements were collected 6 months later to predict air concentrations. Predicted concentrations near the source ranged from 0 to 320 mg/m3, and for the rest of the plant from 0 to 2.8 mg/m3. Concentration measurements were taken but were not available until after the predictions were made. The measured concentrations near the source, 41 to 360 mg/m3, were in the same range as the predicted values and were also correlated with the predicted concentrations (slope=1.1, r2=0.66, p <0.05). Concentrations distant from the source ranged from 0.96 to 2.8 mg/m3. Workers' exposures were predicted using records of their activity and the average modeled concentrations near and distant from the source. The predicted exposures compared reasonably well with personal samples taken during the time period modeled. Predicted exposures were 61 and 20 mg/m3, actual exposures 23.5 and 20.5 mg/m3.