Rain-out and water damage are large contributors to machine failures. The PR System One 50 Series humidifier and water chamber are breakthroughs in delivering consistent humidity without compromising water management. System One and Dry Box Technology make it possible for the PR CPAP machines to be virtually spill-free. This humidifier can be tilted, shaken, or turned upside down without water leaking back into the device. This humidifier is only compatible with Respironics 50 Series machines.