To analyse the optimal condition of photocatalytic removal of indoor air contaminant by air cleaner, an experimental system of photocatalytic degradation of HCHO was constructed and two photocatalytic TiO2 films were coated by dipping method on the granular active carbon and the netlike active carbon,respectively. The results showed that the photocatalytic removal of HCHO was controlled by mass transfer process and pho- tocatalytic reaction process in the higher HCHO concentration,and the photocatalytic rea...