A novel titanium dioxide-coated cordierite foam (TiO2/cordierite foam) was developed for use in air cleaners. By a simple impregnation procedure, TiO2 nanoparticles were immobilized firmly onto the surface of a cordierite foam substrate through high-temperature (500 degrees C) calcination. The strong bactericidal performance of the fabricated foam was evaluated by a newly developed test method for complex three-dimensional through-pore structures. This method could trace 5-6 log units of decrease in bacterial cell numbers in an air environment, thus meeting the criteria of both the JIS and ISO standard test methods. With 0.25 mW cm(-2) of UV-A irradiation for 24 h, the bactericidal rate of the TiO2/cordierite foam exceeded 99.9% for five types of airborne or droplet-based infectious pathogens: Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Legionella pneumophila (L pneumophila), Klebsiella pneumoniae (K. pneumoniae), and methicillin-resistant Staphylococcus aureus (MRSA). The results of repeat testing, where the same sample was used three times, revealed that the bactericidal rate for E. coli was maintained at 99.9% in the second and third use, indicating that the TiO2/cordierite foam possesses a long-term bactericidal action. The TiO2/cordierite foam also exhibited a high photocatalytic degradation capability on gaseous acetaldehyde, which is associated with sick building syndrome, and volatile organic compounds to generate CO2 and H2O. The results demonstrated that TiO2-coated cordierite foam has great potential for use in air-cleaning filters with not only high bactericidal performance to remove pathogens in the air and in droplets, but also strong decontaminating and deodorizing functionality. (C) 2011 Elsevier B.V. All rights reserved.