1. A life saving air-jacket

2. The heater core is thermally insulated by an air jacket from an exterior case.

3. Here, a silencer chamber (10) which is provided is partially or completely surrounded by a cooling air jacket chamber (20).

4. The cooling air jacket chamber (20) can be traversed by a cooling air flow (29, 29') which is driven by the exhaust-gas flow (49, 49').