A New Method for Determining the Initial Mobile Formaldehyde Concentrations, Partition Coefficients, and Diffusion Coefficients of Dry Building Materials

摘要

The initial mobile formaldehyde concentration, C_(m,o); the partition coefficient, K; and the diffusion coefficient, D, of a dry building material are key parameters to characterize formaldehyde emissions from the building material. The solvent extraction method and direct thermal desorption method can overestimate C_(m,o) because of high temperature. A new method has been developed to determine C_(m,o) under similar conditions to common indoor environment, together with K and D. In the proposed method, the tested materials are placed in an airtight environmental chamber for which the temperature can be controlled by a water bath, then the materials undergo a multisorp-tion/emission process and the instantaneous formaldehyde concentration in the chamber is recorded. The K and C_(m,o) are determined from the equilibrium concentrations after every sorption by means of the linear least-square regression, and D is obtained by fitting the concentration at the emission stage into a mass-transfer-based model in the literature. Four kinds of wooden medium-density boards are tested. The C_(m,o) measured using this method is the mobile formaldehyde concentration in the material, which differs significantly from the total formaldehyde concentration in the material measured by using the traditional method recommended by the Chinese standard (GB/T 17657-1999) extraction method. This means that the mobile formaldehyde takes only a small portion of the total quantity in the tested material. The K, D, and C_(m,o) values measured using this new method are used to predict formaldehyde concentrations for sorption processes. The results agree well with experimental data. In addition, some factors influencing the accuracy are analyzed.