A decomposition unit which is suitable for the decomposition of a gaseous undesired component present in a gas stream comprising: i) a flow-through decomposition chamber in which the undesired component is decomposed and which has an outlet and an inlet, and ii) a heating arrangement, and iii) a flow line passing through the heat exchanger and the decomposition chamber via its inlet and outlet. The characteristic feature of the heating arrangement is that it comprises A) a regenerative heat exchanger which in the flow line downstream of the regenerative heat exchanger creates repetitive puffs containing the undesired component to be removed, and B) a puff filter connected to the flow line at a position downstream of the regenerative heat exchanger, said puff filter a) being capable of removing the undesired component in said puffs, and b) typically comprising a container in which the undesired component is removed from the puffs and has an inlet end and an outlet end.
