Hydrogen sulphide (H2S) is a gas which if dissolved in water smells like rotten eggs. The easiest way to remove the smell of small amounts is to aerate the water or pass it through carbon. In conventional carbon filters the carbon gets saturated and regularly needs replacing. In this novel system the H2S is sprayed through a layer of air held in the top of the vessel oxidising the gas vastly improving the capacity of the carbon reducing the need and cost of replacement carbon.