Abstract: The invention relates to a process and a device for burning oxidizable components in a vehicle gas to be purified, comprising a gas inlet (36), a burner (19) with an attached flame pipe (22) opening into a main combustion chamber (24) comprising a bottom and side walls, an annular chamber leading from the side of the main combustion chamber bottom (21), a heat exchanger (32) around which flows the purified gas and through which flows the gas to be purified, and a gas outlet (38). To obtain good combustion with a compact construction, especially to make the best possible use of the geometric dwell time in the main combustion chamber, it is proposed that the main combustion chamber be constructed in such a way and/or has such guide components (40,42,44) that the gas flowing from the bottom towards the annular chamber is distributed completely or largely uniformly over the cross-section of the main combustion chamber.