TiO2 photocatalyst was prepared by hydrothertual method using titanium isopropoxide as a precursor. This photocatalyst had higher content of anatase structure and larger surface area than commercial P-25 photocatalyst. The air purification device with a filter coated with photocatalyst film was excellent in its capabilities to decompose organic materials and to kill germs. When the device was installed in hospitals, it was powerful for the sterilization of floating germs in the air. In addition, the number of germs after 7 months operation was almost the same as that obtained in the first operation. (c) 2005 Elsevier B.V. All rights reserved.