The auto mode of the air purifier is designed to deliver optimised indoor air quality. When the air purifier detects that the air quality is beginning to deteriorate, it automatically increases the fan speed to bring the air quality back to the optimum level. This action protects you from potential airborne risks that are not visible to the human eye.
If you find that the air purifier is too loud, change the fan speed to a lower level or the mode to sleep.
For Philips Air Purifiers AC30XX, AC38XX and AC42XX, you have an option in the mobile app to indicate your main concerns when you set up the air purifier. If you have chosen pollen or dust mites, the device works with a higher fan speed to minimise your risk towards airborne allergens. If you find it too loud, you can use the app to change your main concern to 'Dust and haze/smog/PM2.5'. However, we recommend that you do not change the settings if you suffer from airborne allergy.