Based on the pollution levels of the installation location, the Pre-Filter should be changed or cleaned every 6-12 months. Before it has to be changed, the Cell will last 2.5 years. These times are based on constant usage 24 hours a day, seven days a week. The P series purifiers feature indication lights that alert the user whenever the Cell or Pre-Filter needs to be replaced. In only a few minutes, you can change the Pre-Filter and Cell.