The LPG cooking gas contains propane and butane as the constituents. A sulfur containing compound is added to the LPG, because

Liquefied Petroleum Gas (LPG) is primarily composed of propane and butane, which are naturally odorless and colorless hydrocarbons [1]. Because these gases are highly flammable and pose a significant explosion risk if they accumulate, a safety measure is required to alert users of leaks [4]. A sulfur-containing compound, most commonly ethyl mercaptan (also known as ethanethiol), is added as an odorant [3]. This compound has an extremely low odor threshold and a distinctive, pungent smell often described as skunk-like or rotten eggs. The primary purpose of this additive is to facilitate the easy detection of gas leakage by providing a warning scent, as the base hydrocarbons cannot be detected by the human nose [4]. It does not affect the efficiency, cost, or liquefaction process of the fuel.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.2.2 Chains, Branches and Rings > p. 64
2. [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC10504204/
3. [2] https://www.sciencedirect.com/topics/engineering/odorization
4. [3] https://nj.gov/health/eoh/rtkweb/documents/fs/0894.pdf