Solution:concept - LPG gas is essentially propane and butane and is odourless in its natural state. LPG is very dangerous because if it leaks, it can cause terrible fires and destructive explosions.
The smell you notice when there is a leak is an entirely different agent called Ethyl Mercaptan. This substance is added to the gas as it leaves the main storage terminals.
To prevent damage due to LPG leaks, Ethyl Mercaptan is added to the gas, which has a strong smell of rotten cabbage. This smell helps us detect whenever there is a leak, which makes a lot of sense in terms of safety and security. Thus, Ethyl mercaptan is used to detect leakage of LPG.
Hence, the correct option is (3).