Study On Characteristics Of Volatile Organic Compounds Emission From Dry Building Materials

Volatile organic compounds (VOCs) emitted from building materials furniture and equipment are recognized as major problems affecting human comfort, helth and productivity. For the purpose of controlling indoor VOC concentration, it is necessary to their emission characteristics. In this paper, the characteristics of VOCs emission are studied and it's applications to determine building materials' parameters in experiments are analyzed. The thesis covers four chapters.Chapter one introduces the importance of the research and reviews the recent investigation relating to this research in the literature available. The main objective of this thesis and the importance of the research are stated. In Chapter two, a new and generally applicable model for calculating the surface emissions of VOCs from single-layered, dry building materials is developed. Different form the mass transfer-based models in the literature, the new model does not neglect the mass transfer resistance through the air phase boundary layer and does not assume that the initial VOC concentration distribution (C0(x)) in the building materials is uniform, and provides an analytical solution for this model. For the specific case that C0 is uniform, the proposed model is validated with experimental data.By normalizing the model, factors of influencing the surface emissions of VOCs from building material are clarified and the influences are quantitatively analyzed. It is found that the dimensionless emission rate of VOCs is just the function of Bim (the Biot number for mass transfer)/K (the partition coefficient) and Fom (the Fourier number for mass transfer), which summarizes the general surface emission characteristics of VOCs from building materials and provides the basis for fitting experimental data to formulate empirical correlations of VOC emissions. Based upon the model and the analysis, the applicable condition of the famous Little's model is presented.By using numerical results, correlations describing the VOC emission characteristics are developed and the using conditions are analyzed. The criterion of emission ending: Fom=2.0 is found.By using different distribution of initial VOC concentration in building materials, the influence of initial VOC concentration on VOC emission characteristics is clarified: the influence of initial distribution on emission characteristics decreases with increasing time. When time is less than tc, the influence is strong and should be considered. After that period, such influence can be neglected. And tc is mainly influenced by L and D, therefore, the influence of the initial VOC concentration distribution on the emission characteristics is determined by the physical properties of building materials. For the long-term emission prediction cases that the material thickness is relatively small and the diffusion coefficient is relatively large, it would be justified to neglect the effect of initial VOC concentration distribution on emission characteristics.Applying the analytical model, combined with the chamber test experiment, a new method to determining emission parameters of building materials: C-History Method was presented in chapter three.The last chapter, chapter four, summarizes the conclusions of this research and puts forward the work need further researches in the future.