VOC Emission Characteristics From Building Materials: Measurement, Micro-mesocosmic Interpretation And Simulation

Indoor air quality (IAQ) significantly influences people's health, comfort and productivity, and volatile organic compounds (VOC) emitted from building materials is recognized as one of the main reasons causing poor indoor air quality. Therefore, it is very important to study the VOC emission characteristics. For the previous researches on this problem, there are some shortcomings: (1) Most of the researches are limited to macrocosmic level; (2) It is lack of effective and fast method to measure the key emission parameters, such as initial emittable concentration; (3) The relationship between the initial emittable concentration and total concentration is unclear. Consequently, it makes the prediction and control of emission characteristics, and chosen of building materials lack of reliable evidence and technical tools. This thesis studied the addressed problems well, and the main academic contributions are as follows:Firstly, a novel method, multi-emission/flush regression method (MEFR method) is proposed to simultaneously determine the initial emittable concentration and partition coefficient of VOC in building materials. The method is simple, time-saving and has high accuracy. Based on the proposed method, it is observed that the initial emittable concentration increases significantly with increasing temperature, and it is far less than the value measured by perforator method recommended by Chinese National Standard which measures the total concentration of formaldehyde in building materials, and the ratio is no more than 10% at room temperature (25.2℃). From the viewpoint of heterogeneous adsorption on porous media and microcosmic kinetic energy distribution, the discrepancy between the initial emittable concentration and total concentration has been interpreted, and the characteristic parameter describing the energy heterogeneity of porous media has been obtained, which can provide guidance for formaldehyde emission prediction and evaluation from building materials.Secondly, the VOC emission characteristics in porous building materials are analyzed from the mesocosmic level. Through the observation of scanning electron microscopy (SEM) and mercury intruding porosimetry (MIP) experiments, it is found that the series connection between macro and meso pore is the main diffusion path for VOC diffusing in materials. Based on this, a macro-meso two-scale model is developed to predict the effective diffusion coefficient. The value can be conveniently obtained by measuring the mesocosmic structure parameters, which offers theoretical reference for predicting and controlling VOC emission characteristics.Thirdly, a fully analytical solution describing VOC emission in static chamber is deduced, and it is validated by experimental data. By virtue of the solution, together with parameter regression, a group of dimensionless correlations for predicting emission rate is obtained. By means of the correlations, the results of a given material in a test chamber can be conveniently scaled to those under real conditions.Finally, a static chamber partial-C-history method is presented to fastly determine the key emission parameters (initial emittable concentration, partition coefficient and diffusion coefficient). This method needs very short time to perform (≤24h) and the precision can meet the requirement of engineering application. It provides technical tools for furniture labelling.