Generation and Measurement of Chlorine Dioxide Gas at Extremely Low Concentrations in a Living Room: Implications for Preventing Airborne Microbial Infectious Diseases.

BACKGROUND/AIMS: Preventing respiratory diseases caused by airborne microbes in enclosed spaces is still not satisfactorily controlled. At extremely low concentrations (about 30 parts per billion), chlorine dioxide (ClO2) gas can inactivate airborne microbes and prevent respiratory disease. It has no toxic effect on animals at this level. However, controversies still remain regarding how to measure concentrations of ClO2 gas at such low levels. It is therefore necessary to prove that measured gas concentrations are accurate and reproducible. METHODS: ClO2 gas was released from a gas generator and its concentration was measured by a novel highly sensitive gas analyzer. We compared its data with those from ion chromatography. RESULTS: We demonstrate that the gas concentrations measured in a room using the gas analyzer are accurate and reproducible after comparing the results with those from ion chromatography. However, the temperature dependence of the gas analyzer was found. Therefore, data correction is required for each temperature at which gas concentration is measured. A theoretical analysis of the gas concentrations predicted by the rate of ClO2 gas released from the ClO2 generator was also performed. CONCLUSION: Our results advance progress toward using low concentration ClO2 gas to prevent airborne infectious diseases such as influenza.

Inactivation of Airborne Bacteria and Viruses Using Extremely Low Concentrations of Chlorine Dioxide Gas.

Infectious airborne microbes, including many pathological microbes that cause respiratory infections, are commonly found in medical facilities and constitute a serious threat to human health. Thus, an effective method for reducing the number of microbes floating in the air will aid in the minimization of the incidence of respiratory infectious diseases. Here, we demonstrate that chlorine dioxide (ClO2) gas at extremely low concentrations, which has no detrimental effects on human health, elicits a strong effect to inactivate bacteria and viruses and significantly reduces the number of viable airborne microbes in a hospital operating room. In one set of experiments, a suspension of Staphylococcus aureus, bacteriophage MS2, and bacteriophage ΦX174 were released into an exposure chamber. When ClO2 gas at 0.01 or 0.02 parts per million (ppm, volume/volume) was present in the chamber, the numbers of surviving microbes in the air were markedly reduced after 120 min. The reductions were markedly greater than the natural reductions of the microbes in the chamber. In another experiment, the numbers of viable airborne bacteria in the operating room of a hospital collected over a 24-hour period in the presence or absence of 0.03 ppm ClO2 gas were found to be 10.9 ± 6.7 and 66.8 ± 31.2 colony-forming units/m3 (n = 9, p < 0.001), respectively. Taken together, we conclude that ClO2 gas at extremely low concentrations (≤0.03 ppm) can reduce the number of viable microbes floating in the air in a room. These results strongly support the potential use of ClO2 gas at a non-toxic level to reduce infections caused by the inhalation of pathogenic microbes in nursing homes and medical facilities.