LPG - Propane Gas Smell: Ethyl Mercaptan - What Does Natural Gas Smells Like
LPG (propane) smells because an odourant - Ethyl Mercaptan - is added to the gas to make it easier to detect a leak. Natural gas smells like the same aroma, as the same odourant is used. In their natural state, LPG (Propane and Butane) and Natural Gas (Methane) smell like nothing, as they are all odourless gases and are also referred to as natural gas liquids – NGL.
The distinctive LPG smell that people associate with these gases is actually added to them as a safety measure. Ethyl Mercaptan is the odourant added to make LPG (propane) and natural gas smell like their distinctive aroma.
This odourant is added to the gas as it leaves the main storage terminals.
Most people describe the smell as either rotten eggs or rotten cabbage.
There are certain end products that require odourant free LPG, such as hair spray or deodorant that use LPG as a propellant.
Some people cannot smell the odourant and must rely on electronic leak sensors.
Let's look at some more of the details…
What Does Propane (LPG) & Natural Gas Smell Like?
For many decades, the gaseous fuels industry has added odourants to make LPG and Natural Gas smell like rotten cabbage so that people can detect gas leaks with nothing more than their noses.
Most people t hink that LPG and natural gas smell like either rotten cabbage or rotten eggs.
Without the addition of an odourant, leaking gas could collect without being detected.
This would create a dangerous condition that could lead to an explosion or fire.
The strength of the odourant has caused some people to refer to the process of adding the odourant as “stenching”.
Which Gas is Mixed with LPG to Detect Smell? Odour Additive
Ethyl Mercaptan is the odourant added to make LPG (propane) and natural gas smell.
However, Ethyl Mercaptan is not a gas, it is a chemical oudourant.
Much research has gone into the science of odourants and Ethyl Mercaptan is almost universally recognised as the best choice.
As a result, it is the most commonly used odourising agent.
Ethyl Mercaptan in Propane
Ethyl mercaptan in propane is also known as Ethanethiol. It is a sulfur compound with the chemical formula CH3CH2SH that is a clear liquid with a very strong and distinctive odour. Ethyl mercaptan is commonly used as an odourant with natural gas and propane-LPG, as they are naturally odourless.
How & When it Gets Added
In the case of LPG, the Ethyl Mercaptan is added to the gas as it leaves the main storage terminals.
The amount added and the process are both carefully controlled.
The terminals themselves have gas detectors that can identify gas leaks without any odourant having been added.
Ethyl Mercaptan is Used in LPG Because of its Stability Over Time
Ethyl mercaptan (not methyl mercaptan) is used in LPG as an odourant to generate the telltale smell. Ethyl Mercaptan will maintain the chemical equilibrium across the liquid and vapour space.
However, if the tank liquid level is low, and much of the tank surface inside is exposed, then a small amount of odourant fade MIGHT occur, reducing the overall concentration of the Ethyl Mercaptan in both liquid and vapour LPG.
Given the detectability of the odourant is much less than the dosing used in Australia (we can detect parts per billion, and we dose in parts per million), the small amount of fade should not be an issue.
Methyl Mercaptan Used in LPG
Methyl mercaptan is not used in LPG. People get confused between Ethyl Mercaptan, which is used as an odourant in LPG, and Methyl Mercaptan, which is not used in LPG. Methyl mercaptan reportedly used as a dietary supplement for animals.
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