The Humidifier Pressure Valve is designed to help prevent water or oxygen from flowing into a CPAP or BiPAP machine from the hose or humidifier. When the machine is turned on the air flow passes through the valve from the machine to the air pathway. When the machine is turned off the Pressure Valve prevents oxygen or water from flowing back into the machine. The Pressure Valve is compatible with any CPAP or BiPAP machine being used without a humidifier, or if the machine is being used with a stand alone humidifier. It's an added defense against costly damage that can sometimes happen when a CPAP unit is exposed to water. This product includes the Humidifier Pressure Valve alone, and does not come with any other parts or accessories. What's Included: Humidifier Pressure Valve General Tips Section The Pressure Valve attaches directly to the machine and allows a stand alone humidifier or long CPAP hose to attach to it. The valve is trouble free and keeps water or added oxygen out of the machine. NOTE: The valve MUST be installed directly onto the machine to prevent the flow of water or oxygen back into the machine. 302418