Recently, heterogeneous photocatalytic detoxificationmethodologies proved very promising for the treatment anddisinfection of contaminated air. It is well established thatinitiation of photocatalytic degradation of paint layers containingΤiO2 is quite different from that of layers withoutΤiO2. Since TiO2 is broadly used in modern and contemporarypictorial art, acting both as a pure white pigment or amoderator of hue and saturation, the present paper is tr yingto investigate the dioxide’s role in the inherent protectionof polychrome works of art, proposing an additionalapplication of heterogeneous photo catalytic decomposition(TiO2/UV-A). For testing the possibility, Hansa yellowand verdigris were selected as two colourants bearingextensively studied degradation processes, and havingstructures easily correlated to further chemically relatedpigments. Various types of TiO2, in rutile form or as a mixtureof rutile/anatase, were examined at several light intensitiesas to their role in protecting or not Hansa yellow andverdigris. In order to reproduce a sequence of typicalindoor environments, the induced difference was measuredwith reference to samples not containing TiO2 on a seriesof experimental simulations of paintings at various proportionsof TiO2/colourant, placed in an isolated chamber filledwith contaminated air and irradiated.