Abstract of Disclosure In a treatment method of room air by air ionization, sensors such as air-quality sensors, an airflow sensor, an air humidity sensor, an ozone sensor, are provided. Parameters such as oxidizable air components, relative humidity, flow velocity, flow volume, ozone level, and intensity of oxygen ions are measured. The level of ionization power of the ionization apparatus is determined by an electronic control device based on the measured parameters. The ionization power is lowered, when a predetermined ozone value is detected, and, when the ozone level continues to increase after lowering the ionization power indicating an external ozone source, ozone decomposition is initiated by changing a time period of the applied periodic alternating voltage, supplied in the form of alternating pulses or packages of alternating pulses of a preset number or a combination of alternating pulses and packages of alternating pulses of a preset number.