Objective To investigate the NOx(nitrogen oxides,esp.NO2) output of household ozone generator and the control method.Methods Ion chromatogram,pH detection and iodine titration were used to study the outputs of ozone and the by-product,NOx,generated by some certain household ozone generator in normal operation condition.The method of controlling NO2 simply by pure water absorption was also studied.Results At about 15 min,the ozone generator produced NO2 and turned into NO3-,the amount increased along with the operating time.After 60 min,the NO3-was almost in proportion to the operating time,the pH value decreased clearly.pH value was a proper and simple substitute parameter to display the generation and accumulation of NO2.NO2 could be efficiently controlled by pure water absorption.NO3-absorbed in a 0.1 mol/L NaOH solution was less than 0.01 mg/L after a pure water absorber which had an effective depth of 12cm,with little influence of ozone production.Conclusion NO2 will be generated inevitably and the amount of the by-product increases with the running time of the household ozone generator.Pure water absorption is efficient to control NO2 generation.