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Why are thiols added to natural gas as warning odorants?

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A labeled diagram highlights sulfur's position on the periodic table, showing its atomic number 16, symbol S, atomic weight range, electron configuration, and classification as a solid, strongly acidic, orthorhombic nonmetal at room temperature. — sulfur Chemical properties of sulfur.

Natural gas is primarily composed of methane, which is both colorless and odorless. Because of this, leaks can be difficult to detect, posing a significant safety risk.1

To ensure the rapid detection of any leakage during transport or use, a minute quantity of a thiol—often referred to as a mercaptan—is added to commercial natural gas. Thiols are organic sulfur compounds known for their strong, repugnant, and distinct odors, which humans can detect at extremely low concentrations, such as a few parts per billion. By adding these compounds, the gas is given a characteristic "rotten-egg" or skunky smell that serves as an effective warning agent for potential hazards.2345