Influence of local airflow on the pollutant emission from indoor building surfaces

This article reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general un derstanding of the mechanisms involved in the emissions from building mater ials in ventilated rooms. In addition, a generally applicable method for th e prediction of surface emissions is proposed. The work focused on the emis sion of vapours and gases and no particulate emissions were considered. The methods used were numerical calculations by computational fluid dynamics ( CFD) and full-scale laboratory experiments. It was found that the emissions are a strong function of air-change rate, local air velocity and local tur bulence, as the mass transfer coefficient increases in proportion to these parameters. The findings further show that the mass transfer coefficient in creases in proportion to the velocity when the emission is controlled by ev aporation from the surface. With regard to diffusion-controlled emissions, the mass transfer coefficient is unaffected by the velocity.