Ethyl Mercaptan is a highly flammable liquid having low boiling point of 35 Dec C and flashpoint below -45 Deg C (closed cup). This chemical, Ethyl Mercaptan, has a very unpleasant odor which Guinness Book of World Record identifies as the smelliest substance in the world.
Ethyl Mercaptan is added to LPG (Liquefied Petroleum Gas) intentionally to warn us when there is a leakage since we can immediately detect the bad smell of Ethyl Mercaptan.
In IMDG Code Ethyl Mercaptan is listed under UN 2363 Class 3 Packing Group I
IMDG Code Compliance Centre 