Apparatus is described for treating an effluent fluid stream from a semiconductor manufacturing process tool. The apparatus comprises a combustion chamber, means for heating the combustion chamber, and a nozzle for injecting the effluent stream into the combustion chamber. The apparatus is configured to enable a fuel and an oxidant to be selectively injected into the effluent stream as required to optimise the combustion conditions for a particular effluent stream. In one to embodiment, a lance projecting into the nozzle selectively injects an oxidant into the effluent stream, and a sleeve surrounding the nozzle selectively injects a fuel into the effluent stream.