Ozone produced from photocopier, car exhaust and electric welding is harmful because this e exhaust gas mot just o3 also have carbon power, fine particles. Ozone gas from ozone generator is very pure. Ozone contains a lot of nitrogen oxides and other impurities, nitrogen oxides, dust particles harmful to human respiratory tract, nervous system and other harm, so the ozone produced by photocopiers, car exhaust, which contain large amounts of impurities, the human body is not good.