I purchase this Philips air purifier one month ago. I am totally disappointed with its performance. My room size is 120 square feet. which this purifier is unable to provide clean and safe air level. The air quality indicator never shows good air quality level ( blue) even after whole night operation. It generally remains in very unhealthy or unhealthy level. The purifier remains totally ineffective during night sense mode. I did not expect this quality from Philips. Totally waste of money.