Effects of various indoor environmental factors on the decay of chlorine dioxide gas concentration: Implications of its use against pandemic influenza

Abstract

Air-cleaning systems using a low concentration of chlorine dioxide (ClO₂) gas for prevention against infection by the influenza virus have been developed. ClO₂ gas is easily decomposed by indoor climate factors. Three experiments were conducted to evaluate the effects of indoor environmental factors on the decrease of ClO₂ gas concentration. The reaction (decay) rate constant was also determined. High air temperatures and light irradiation accelerated the decrease of ClO₂ gas concentration; the latter had the greatest influence on the decrease of ClO₂ gas concentration among the conditions. A quicker decay of concentration and greater value of the reaction rate constant of ClO₂ was found when a UV lamp was used; this is because the gas absorbs irradiation in the UV range. ClO₂ gas concentration was significantly reduced when an evaporative humidifier was employed due to adsorption and a chemical reaction between the gas and the filter in the humidifier.

Acknowledgments

The authors would like to express their sincere gratitude to Mr. Y. Ezaki, Mr. M. Tatsuki, Ms. H. Takeuchi, and Mr. Y. Yokota of Waseda University for their assistance with the planning and execution of this research. Also to acknowledged are Prof. Y. Aikawa of Ochanomizu University and Dr. N. Ogata and Dr. S. Asada of Taiko Pharmaceutical Co., Ltd. for their advice.

Hitomi Tsutsumi, PhD, is Visiting Lecturer. Fumihiko Shinoda is Master Student. Shin-ichi Tanabe, PhD, Fellow ASHRAE, is Professor. Masakazu Setsujima is Assistant General Manager. Kouichi Nakahara is Engineer.