The prospects for photocatalytic purification and treatment of air depend centrally on finding conditions for which the apparent photoefficiency for contaminant disappearance is near or above 100%. We recently demonstrated that destruction of a low photoefficiency contaminant, toluene, by addition of a high photoefficiency compound, trichloroethylene, could raise the toluene photoefficiency to provide 100% conversion in a single pass, fixed bed illuminated catalyst, using a residence time of about 5-6 ms. The present paper establishes the generality of this TCE enhancement of contaminant rate and photoefficiency by examining the photocatalytic oxidation of various common contaminants at 50 mg/m(3) in air, including alcohols, aldehydes, ketones, aromatics, and chloroalkanes using near-UV-illuminated titanium dioxide powder in a flow reactor, in the absence and presence of trichloroethylene (TCE). Compounds exhibiting TCE rate promotion were toluene, ethylbenzene, m-xylene, methyl ethyl ketone (MEK), acetaldehyde, butyraldehyde, methyl tert-butyl ether (MTBE), methyl acrylate, 1,4-dioxane, and hexane. Rate inhibition by TCE was exhibited for acetone, methylene chloride, chloroform, and 1,1,1-trichloroethane. TCE presence had almost no effect on the benzene and methanol rates. Butanol and vinyl acetate single component conversions were 100% under our standard low flow rate conditions; increasing the flow rate quenched TCE conversion in the presence of butanol, and therefore no TCE enhancement effect could be noted.