EVALUATION OF EVAPORATION AND CONCENTRATION DISTRIBUTION MODELS - A TEST CHAMBER STUDY

Occupational exposure to airborne volatile organic compounds is govern ed by the source strength and dispersion of the pollutant into workroo m air. The purpose of the present test chamber study was to validate s uggested models for the prediction of evaporation rates and concentrat ion distributions. The study design was organized into different scena rios to simulate workplace conditions. Evaporation rates of organic co mpounds of different volatilities were recorded gravimetrically and th e corresponding concentrations in air were measured at various locatio ns equally distributed in the test chamber. The evaporation models gen erally showed a fair agreement with experiments but tended to underest imate the evaporation rate especially at low air velocity. Based on fa ctorial experiments a new simple evaporation model was suggested. The performances of the concentration distribution models were of differen t quality. The model developed by Roach (Annals of Occupational Hygien e 24, 105-132, 1981) cannot be used in predicting the concentration di stribution in case of a convective air flow. If knowledge of the evapo ration rate and pollutant concentration at some distances from the sou rce were available, the model suggested by Scheff et al. (Applied Occu pational and Environmental Hygiene 7, 127-134, 1992) generated a conce ntration distribution in reasonable agreement with the observed data. The box-model (Sinden, Building and Environment 13, 21-28, 1978) gener ally offered a fair performance but tended to underestimate the pollut ant concentration in a region close to the source in the direction of the main air flow. (C) 1997 British Occupational Hygiene Society. Publ ished by Elsevier Science Ltd.