A method of treating a gas stream containing silane or other silicon-containing gas is described, in which the gas stream is conveyed to a liquid ring pump or screw-mechanism pump, to which are also supplied an oxidant for oxidising the silicon-containing gas within the pump, and a liquid for forming a liquid ring or intermittent flushing within the pump. A liquid stream containing said liquid and a by-product of the oxidation of the silicon-containing gas is exhaust from the pump.