Most of the photocatalytic products currently used are applied primarily in the construction industry in order to reduce environmentally hazardous and toxic harmful substances indoors and outdoors. The standardised nitrogen oxide decomposition test according to ISO 22197-1 is used for the quantitative evaluation of these products. It can be supplemented with application-oriented VOC (volatile organic compound) analysis. Using different reactor types and geometries (flatbed reactor for planar specimens, flow-through reactor for mats or bulk goods) makes it possible to test a wide variety of products.