The generation of ozone in a stable regime of DC corona discharge at a pin electrode is modeled to provide data that can be utilized for the evaluation of charging and transferring devices of electrophotography with respect to reducing the ozone emission. The results of a theoretical investigation show the following: (1) The ozone generation rates of the 50 μm radius pin electrode are 0.085 ppm/μA and 0.010 ppm/μA under 5 liter/min air flow rate in case of negative corona and positive corona, respectively. The generation rate increases in accordance with the increase of the pin radius. Although the rate of ozone emission is nonlinear with respect to the discharge current, it can be assumed to be approximately linear within the usual design and operation conditions of electrophotography chargers. In case of the positive corona, ozone is formed just at the surface of the discharge electrode, but on the contrary, in case of the negative corona, ozone is formed at about 0.1 mm apart from the tip of the electrode. (2) The ozone generation rate of the charger with saw-tooth electrodes is reduced to about one third of that with a biased charger roller and it is only 1/140 of that with a corotron. The sawtooth charger has a potential to realize virtually ozone-free charger.