Bacteria and mould gradually build up in the filters. This causes a deterioration in the air exchange capacity. In addition, the ventilation system becomes noisier if the filters are not changed regularly.
On average, it is recommended to change the air filters at least twice a year. If your region or neighbourhood has poor air quality, you may want to change the filters more frequently, for example if you live in an urban area with a lot of traffic. If you suffer from allergies or asthma, you may need to change the filters after only 2 months.