Accumulation of out-of-service odorant storage vessels is one of the problems in gas distribution system of the country. The absolute majority of gas distribution stations use the odorant MNM – mixture of lower natural mercaptans. Being highly corrosive, odorant MNM promotes rapid accumulation of bottom sludge in metal containers for odorant storage. The bottom sludge consists of corrosion products – pyrophoric iron sulphides. For the purpose of reducing the hazard category of out-of-service odorant storage vessels, the method for their detoxification was developed. It allows effectively reduce the sulfur content in the bottom sludge, so the vessels can be utilized as low-hazard waste.