Lydia this side...Thiols can be found in a wide range of industrial wastes, both liquid and gaseous. Previously, thiols were referred to as mercaptans. Although thiols are toxic, they are usually found in very low concentrations and can be detected by smell at levels far below toxic levels. Because the odor detection levels are in the order of parts per billion, they are not considered hazardous, but rather a nuisance (PPB). The mercaptan removal from lpg are converted to disulphides plus water via oxidation using a liquid catalyst dispersed in a caustic solution. .The spent air is directed to the steam generation unit, while the organic liquid phase, which contains disulphides, is separated from the caustic solution and directed to storage. For further detail have a look on website.