ResMed's Air Outlet Adapter fits on the back of all AirSense 11 Series CPAP machines. The Air Outlet Adapter must be properly installed whenever the CPAP device is in use. USAGE: The Air Outlet Adapter should not need to be removed from your AirSense 11 sleep therapy device unless the adapter is damaged or needs to be cleaned. To remove the Air Outlet Adapter from your CPAP machine, press the release clip located inside the machine (where the humidifier chamber usually sits) and then pull the adapter out through the rear of the device. For complete instructions review the documentation that came with your equipment.