The Philips EverFlow Oxygen Concentrator is a 5-liter Oxygen Concentrator, option for home oxygen machine. The Philips Everflow Inlet Filter reduces the load on the machine and there by reduces power consumption The EverFlo concentrator uses this air inlet filter as a replacement part, which shields the equipment from harmful particles and ensures highly effective operation on a long-term basis. The philips oxygen machine EverFlow inlet filter will need to be replaced every two years, and the filter door needs to be cleaned every month at least. If you are working in a particularly particle-heavy environment, you may need to clean the door and replace the filter more frequently.