An air purifier includes an outer case having an air purifying cavity, an ionizer module, and an ozone reduction module. The ionizer module includes a power unit and an ionizing electrode. The ozone reduction module is electrically connected to the power unit for generating heat within the air purifying cavity, wherein when a temperature within the air purifying cavity reaches a preset temperature, a level of ozone generated by the ionizing electrode unit is substantially minimized and controlled for preventing excess generation of ozone.