Background: The risk of spread of infection through aerosols generated by ultrasonic scalers is a major concern in the dental community. The aim of this pilot study was to evaluate and compare the efficacy of different pre-procedural mouthrinse in reducing the levels of viable bacteria in aerosols and the efficacy of chlorine dioxide as an effective alternative. Materials and methods: Study included 21 systemically healthy patients with chronic periodontitis and divided randomly into three groups (l, ll, and lll) of seven patients each to receive 0.2% chlorhexidine gluconate, chlorine dioxide (ClO2) and water, respectively, as a pre-procedural rinse. Aerosols produced by the ultrasonic unit were collected at three different locations, on blood agar plates in all three groups. The blood agar plates were incubated, and the total number of CFUs was counted and statistically analyzed. Results: The results showed that CFUs in groups l and ll were significantly reduced when compared with group lll, p <0.001 (analysis of variance ANOVA). But on comparing group l and ll, p> 0.05 value was found to be non-significant. The numbers of CFUs were the highest at the patient’s chest area and lowest at the assistant’s chest area. Conclusion: This study suggests, use of pre-procedural mouthrinse could significantly eliminate the majority of aerosols generated by an ultrasonic unit, and that ClO2 mouthrinse was found to be equally effective in reducing the aerosol contamination to 0.2% CHX gluconate.