What is Mercaptan?
Natural gas is one of the safest, most efficient and most reliable forms of energy available. But, like any energy source, natural gas must be used properly.
Since natural gas is colorless and odorless, we add a harmless, non-toxic chemical that makes it easier to detect a gas leak before it can create a hazardous situation. The chemical, called mercaptan, smells a lot like rotten eggs. If you aren't familiar with it, call Columbia Gas of Massachusetts at 1-800-688-6160 and ask for a "scratch-n-sniff" card that provides you with a sample of the odor.
In a concentrated form, the smell is almost unbearable. And it takes only a few parts per million of mercaptan to give natural gas a smell. That is precisely why we add it to natural gas. If we did not add mercaptan, it would be hard for you to know that unlit natural gas was coming from your stove after you left the valve turned on. And leaks from furnaces and hot water heaters would be nearly impossible to detect without expensive equipment. So mercaptan's smell is a very valuable safety feature.
Mercaptan contains sulfur. That's what makes it smell. The kind we use blends well with natural gas and, in a gaseous state, has much the same properties as natural gas, so it will also rise and dissipate with natural gas.
There are other uses for mercaptan in industry, including jet fuel, pharmaceuticals and livestock feed additives. It is used in many chemical plants. Mercaptan is less corrosive and less toxic than similar sulfur compounds found naturally in rotten eggs, onions, garlic and skunks.