Philips AC4014 Air Purifier with advanced filtration system smart sensor gives accurate feedback on indoor quality of air. The advanced filtration system eliminates harmful agents , bacteria and allergens in three stages. HEPA Filter with its anti bacterial coating filters out fine dust and eliminates germs and mould.. Healthy air protect alert gives you a timely warning to replace the filter. 3-step light indicator clearly shows air quality level: Blue-Good, Purple- Fair, Red-Bad. Appliance operates for a set of hours and automatically switches off when set time has elapsed.