Mechanism And Experimental Study On VOC Emissions From Building Materials

Volatile organic compounds (VOC) emitted from building material have been recognized as major problems affecting indoor air quality and human health, but the emission mechanism of VOC emission from building materials is not clear. It is important to study emission characteristic of VOC from building materials. The emission mechanism of VOC from building materials was studied theoretically and experimentally.An approximate integral method for predicting volatile compounds emission from plate was presented. The gas-phase mass transfer resistance is neglected for simplifying computation. Compared with Laplace Transformation Method, the method suggested is simpler. The emission flux, chamber concentration of volatile compounds and concentration distribution of volatile compounds in the material can be determined conveniently. Results of the present method are in good agreement with experimental data.The diffusion coefficient of VOC in building materials, partition coefficient, and initial concentration of VOC in building materials are the three key parameters used to predict VOC emissions from building material. The diffusion coefficient and partition coefficient are affected strongly by temperature and relative humidity. In this thesis, a small environment chamber is used to study the influence of temperature and relative humidity on VOC concentration curve in chamber. The diffusion coefficient, partition coefficient and initial concentration of VOC can be obtained by the least square fitting. The influence of temperature and relative humidity on diffusion coefficient and partition coefficient is also analyzed.A new mass transfer model for estimating the emission of VOC from fresh wet building materials was developed. Different from the mass transfer-based models in the literature, the dry period of wet material during the process of VOC emission from wet building material is considered in the new model and the effect of saturated vapor pressure at surface of wet building materials on process of VOC emissions is analyzed. When wet building materials is newly applied, the concentration of TVOC in the building materials gradually decreases as the emission of VOC, and the vapor pressure of VOC at surface of wet building materials decreases. For keeping the partial pressure of VOC at the surface of wet building materials is saturated vapor pressure, the air-wet film interface is lowered and the dry film at the surface of wet building materials is formed. Compared with the results by VB model, Yang's model and experiment data, the results obtained by the present model agree well with the results obtained by Yang's model and experiment data. The present model is more accurate in predicting emission of VOC from wet building materials than VB model. A small environment chamber is used to study the influence of temperature and relative humidity on VOC concentration curve in chamber. The results obtained from experiment can be well explained by dry model.