Abstract: Air pollution, especially particulate matter (PM), is an increasingly urgent problem in urban environments, causing both short and long-term health problems, climate interference and aesthetical problems due to building fouling. Photocatalysis has been shown to be a possible solution to that end. In this work two complementary detection methods for photocatalytic soot oxidation are studied and their advantages and disadvantages are discussed. First, a colour-based digital image analysis method is drastically improved towards an accurate, detailed and straightforward detection tool, that enables simultaneous measurement of the degradation of different grades of soot fouling (for instance a shallow soot haze versus condensed soot deposits). In the next part, a second soot oxidation detection method is presented based on in situ FTIR spectroscopy. This method has the additional advantage of providing more insight into the photocatalytic soot degradation process by monitoring both gaseous and adsorbed intermediates as well as reaction products while the reactions are ongoing. As an illustration, the proposed detection strategies were applied on four different commercially available and synthesized photocatalytic materials. The digital image analysis showed that P25 (Evonik) is the fastest photocatalytic soot degrader of all studied materials for both a uniform soot haze as well as concentrated soot spots. Application of the in situ method showed that for all studied materials adsorbed formate-related surface species were formed and that commercially available ZnO nanopowder has the highest specificity towards complete mineralization into CO2. With this we aim to provide a set of complementary experimental tools for the convenient, reliable, realistic and standardised detection of photocatalytic soot degradation.