The WABCO air handling unit is a multifunctional device that integrates multiple independent units, including air dryers with or without heaters, safety valves, and tire inflation connection devices. It also includes a multi way protection device, as well as one or two integrated pressure limiting valves and two integrated one-way valves, which are connected to the air dryer through flange connection. WABCO's multifunctional APU (Auxiliary Power Unit) is not only affordable and easy to install, but also requires minimal installation space due to its use of an integrated compact unit. In addition, WABCO's air handling unit also has efficient filtration capability, suitable for corrosive environments, and has an electronic air handling unit version that integrates WABCO's fuel saving software in the external ECU, aiming to provide better energy efficiency and performance.