The adsorption and photocatalytic degradation of nerve agent, isopropyl methylphosphonofluoridate, Sarin (GB) as a real Chemical Warfare Agent (CWA) on powdery Titanium dioxide (TiO2) film have been investigated using Gas chromatography/mass spectrometry (GC/MS) analysis in ambient atmosphere. We found that the ability to decontaminate GB molecules on TiO2 photocatalyst can be estimated to be 42 molecules/nm(2), indicating that 1 g of TiO2 photocatalyst can decontaminate 3.4 mmol of GB molecules as the limitation value to maintain the photocatalytic activity. We also elucidated a plausible photocatalytic decontamination mechanism of GB at the surface of TiO2 photocatalyst on the basis of the results obtained in this study. (C) 2011 Elsevier B.V. All rights reserved.