This study reports the design, the development and the application of a novel photo-CREC-air reactor. This photo-catalytic unit operates in a batch mode and features a basket with immobilized TiO2. The TiO2 is supported on a fiberglass mesh and is illuminated externally by eight Pen-Ray((R)) lamps housed in parabolic reflectors. Flow patterns in the illuminated section show good contact between the treated air stream and the photo-catalyst. Two photo-catalysts. Degussa P25 and Hombikat UV-100, were employed with the catalytic activity being tested using acetone as a model pollutant. Special emphasis was assigned to the determination of the influence of several operating parameters including catalyst type, catalyst loading and catalyst attachment to the support. Experimental results showed that, in addition to the catalyst loading, the photo-conversion rate strongly depends on the physical proper-ties of the photo-catalyst such as particle-particle agglomeration and particle-mesh interaction.