An original methodology to predict spacetime concentration distribution of VOC in an enclosed space where a photocatalytic air purifier apparatus is placed is herein presented. This apparatus is specially designed for indoor air treatment. Intrinsic kinetic parameters are first determined in a perfectly mixed batch reactor allowing a direct access to chemical reaction rate with a few experiments. Computational fluid dynamics (CFD) is then used to model fluid flow in the room and calculate spacetime concentration of VOC by setting chemical reaction rate as a boundary condition based on kinetic parameters determined in the batch reactor. Experiments and modelling are performed using acetaldehyde which is a common indoor volatile organic compound and titanium dioxide thin film coated on steel performed by a PVD method. Remediation of acetaldehyde is investigated at low concentration levels, in the low ppm range. Prediction of acetaldehyde removal in the enclosed space is then compared with experimental results allowing validation of the methodology. (C) 2010 Elsevier Ltd. All rights reserved.