A new quantitative screening method for the photocatalytic activity of nanoparticles and powdery materials was developed. With a custom-built apparatus the measurement of the photodegradation of non-volatile organic compounds in dependence of the inorganic photocatalyst and experimental factors like irradiation time, temperature, organic compound, spectral distribution and irradiance is possible. By applying various spectral distributions and irradiances slightly lower than in outdoor conditions, the described method uses application-oriented testing conditions. It can be used for the screening of the photocatalytic activity of newly developed materials towards any carbon containing non-volatile compounds. (C) 2008 Elsevier B.V. All rights reserved.