Air treatment system and method of supplying a brake system of a commercial motor vehicle with compressed air

The air treatment system (10) for the supplying a commercial vehicle's brake system with compressed air has a compressed air inlet (1) connected through respective bypass valves to first and second compressed air outlets, whereby the first outlet is connected to a compressed air receiver and the second to a trailer brake system. A check valve (18) is provided parallel to the first bypass valve (12) and enables a bypassed air flow from the first compressed air outlet (21) through the check valve and shuts off the air flow to the first compressed air outlet. An independent claim is included for a method for the supplying of compressed air to the brake system of a commercial vehicle by means of an air treatment system.