Troubleshooting My Philips Air Purifier's air quality ring colour won't change When the colour of the air quality light ring in your Philips Air Purifier stays the same, there could be several causes. Learn more here. The air quality sensor is dirty The air quality sensor needs to be clean and dry for your Air Purifier to work properly and for the ring to provide the correct indications. Please clean the air quality sensor with moistened cotton buds and then dry it with dry cotton buds. Heavily polluted air is coming into the room When pollution sources are larger than the purification capacity, the air quality light ring in your Philips Air Purifier won't change. One example of this is heavily polluted air coming into the room. To solve this, please make sure all windows and doors are closed. New furniture was added to the room New furniture can emit gases for several weeks. These gases would be sensed by the air quality sensor and the air quality light ring wouldn't change.