Hydrogen sulfide, which is formed in sewer networks in the absence of Oxygen (air), causes heavy odours. The reason for this is a decomposition processes in the collected waste water. As long as there is atmosphere providing some Oxygen for oxidation no hydrogen sulphide forms. When the Oxygen is used up anaerobic conditions are stablished creating the perfect ambient for the formation of H2S, organic Sulphides and Mercaptans. Hydrogen Sulphide is poisonous and has a strong corrosive effect. Standard measures against hydrogen sulfide formation are injection of compressed air, compressed air rinses, adding relevant chemicals and de-odorizing. These measures are often expensive or solve the problem only partially.