Volatile sulphur compounds (VSCs) are responsible for oral malodour (bad breath). There are many otc products for people for use, based on an oxidative reaction system. This paper examines the effect of ozone on VSCs.Objective To test the efficacy of Ozone (O3) dissolved in water on VSCs and the management of bad breath in a small pilot study in a general dental practice environment, test the Halimeter, and test a new bad breath Index, the Ks Index.Method Twenty subjects were recruited into this study. After olfactory assessment, they were assigned to a Ks Index (The Kissability Index) and measured with the Halimeter (Interscan Corp, USA) after calibration, to establish their base‐line VSCs. Each subject gargled with ozonated water for 30 s, and were re‐assessed with the Halimeter. This was repeated after 5‐, 30‐ and 60‐min intervals. Ozone (O3) was bubbled under pressure into 1 l of cooled, distilled water at a concentration of 2100 ppm for 1 min for each subject.Results After just 1 min of gargling and mouth rinsing with 100 ml ozonated water, there was an average VSC reduction of 42.5% from the pretreatment baseline value. Five minutes after treatment, the VSCs rose an average of 14.2%; after 30 min, a further 18.9%, and after 60 min, the VSC values had risen by a further 24.6%. Ozone is a powerful oxidant, and in gaseous form, is used to reverse caries (1). When dissolved in water (maximum 5% volume in distilled, cooled and pressurised water) ozone is safe, and has been extensively used in reducing cfu's in dental water lines (2). Studies in Russia (3) have shown ozone to be an effective oral hygiene adjunct. This study showed that low concentrations of ozonized water is cheap and easy to make. It is a very effective product to reduce VSC's, and further research is proposed in this area.Conclusion Ozone dissolved in water may offer a cheap alternative to the more expensive and less effective commercial mouth rinses to combat bad breath. However it is unstable (half‐life of about 2–3 h if kept cold) and needs to be manufactured when required. It may have a greater role in the control of oral hygiene or as a presurgical mouth rinse.