embodiments of the present invention is shown the muffler 101 comprises a catalyst body 102 arranged in a inner housing 103 with a first open end 104 and a second open end 105 the exhaust gas 106 from the combustion engine not shown enters the muffler 101 at the first open end 104 of the inner housing 103 the exhaust gas outlet from the combustion engine is directly attached to the first open end 104 of the inner housing 103 the inlet channel i e the part of the inner housing upstream of the catalyst body 102 is in this embodiment bent twice in order to minimise the heat radiation from the catalyst body 102 to the first open end 104 and thus protecting the engine not shown from high temperatures the exhaust gas 106 is treated when passing through the catalyst body 102 the treated gas 107 then exits the inner housing 103 at the second open end 105 of the inner housing 103 and enters the front chamber 108 where the gas is cooled due to heat transfer at housing 109 the treated gas 107 is forced to flow through apertures 110 that are arranged close to the housing 109 in an intermediate baffle 111 in order to maximise the cooling of the treated gas by convection heat transfer when passing through the apertures 110 the treated gas 107 enters the rear chamber 112 in the rear chamber there is partly a counter current heat exchange between the exhaust gas 106 entering.