A study of the properties of chlorine dioxide gas as a fumigant

Chlorine dioxide (ClO2) is a strong oxidant that possesses an antimicrobial activity. We demonstrated here that ClO2 gas is easily generated by mixing 3.35% sodium chlorite solution (Purogene) and 85% phosphoric acid at a 10:1 volume ratio without using an expensive machine. In a test room (87 m(3)), experiments were carried out using various amounts of sodium chlorite solution (0.25 ml/m(3) to 20.0 ml/m(3)). The gas concentration increased in a sodium chlorite volume-dependent manner and reached peak values of from 0.8 ppm to 40.8 ppm at 2 h-3 h, and then gradually decreased. No differences in gas concentrations were observed between 0.1 and 2.5 m above the floor, indicating that the gas was evenly distributed. Under high-humidity (approximately 80% relative humidity), colony formation of both Staphylococcus aureus and Escherichia coli was completely inhibited by ClO2 gas exposure at 1.0 ml/m(3) sodium chlorite solution (mean maximal concentration of 3.0 ppm). Exposure at 4.0 ml/m(3) sodium chlorite solution (mean maximal concentration of 10.6 ppm) achieved complete inactivation of Bacillus atrophaeus spores. In contrast, without humidification, the efficacy of ClO2 gas was apparently attenuated, suggesting that the atmospheric moisture is indispensable. Delicate electronic devices (computer, camera, etc.) operated normally, even after being subjected to more than 20 times of fumigation. Considering that our method for gas generation is simple, reproducible, and highly effective at decontaminating microbes, our approach is expected to serve as an inexpensive alternative method for cleaning and disinfecting animal facilities.