“…ClO 2 is a free radical, owing to one unpaired electron in its molecular orbital (ClO 2 : ) (Lynch et al, 1997). Possibly due to its strong oxidizing activity (Moran et al, 1953;Fukayama et al, 1986), when dissolved in water, ClO 2 has potent antimicrobial activity against bacteria, fungi, protozoa and viruses (Taylor & Butler, 1982;Harakeh et al, 1988;Chen & Vaughn, 1990;Foschino et al, 1998;Eleraky et al, 2002;Schwartz et al, 2003;Sivaganesan et al, 2003;Li et al, 2004;Loret et al, 2005;Sy et al, 2005;Wilson et al, 2005;Okull et al, 2006;Simonet & Gantzer, 2006). However, the antimicrobial activities of gas-phase ClO 2 have not been well studied.…”