Development of a model for the estimation of indoor volatile organic compounds concentration based on experimental sorption parameters

In order to model indoor air quality quantitatively, the adsorption and the desorption rate constants of toluene for four typical furnishing materials (namely, two polyacrylonitrile carpets, a cotton sofa and a polyester curtain) were obtained by analyzing the toluene evaporation experiments in a test chamber. The N-2-BET areas were also measured for these materials and they were found to be in the range of 0.5-1.5 m(2)/g. It was found that the constants, at 25 degrees C, ranged between 0.0009 and 0.0013 m* h(-1) for adsorption and between 0.03 and 0.06 h(-1) for desorption, depending on the type of the material. These constants were then incorporated in a model for predicting the toluene concentration as function of time and the theoretical results were compared with the measured data of a test house. The unsteady state mass-balance model which rook into account adsorption and desorption rates and assumed negligible external and internal mass-transfer resistances were found to be satisfactory. Mixing factors were used in expressing deviations from complete mixing in the test chamber, and values around 0.7 were obtained experimentally by the SF6 tracer gas technique. The same technique was also used to measure the hourly air exchange rates in the test house.