What's That Smell? How Natural Gas Is Odorized For Safety

Oct 8, 2015

At one CPS Energy odorization station, this small device dispenses 1 cc at a time of the substance mercaptan into flowing natural gas.
Credit Virginia Alvino / Texas Public Radio News

Natural gas doesn’t smell.  But the practice of adding a rotten egg odor was started decades ago for your safety. 

In 1937, a natural gas leak caused a big explosion, destroying a school in New London, Texas, and killing nearly 300 teachers and students.

Daniel Davila with CPS Energy says that event changed the gas industry forever.

“They began developing different types of odorants that people could readily detect based off of a sulfur product," says Davila. "And its derivative of the oil itself, that they re-inject into the gas that makes it smell like it does.” 

And what it smells like – is kind of like rotten eggs.

CPS operates four primary odorization stations where gas comes in from suppliers, and in accordance with regulations, CPS makes it stink.

At the plant, four storage tanks store the chemical mercaptan to odorize the gas. 

As the gas flows through the pipeline, little drips of the mercaptan are dispersed. Just about two tablespoons is enough to odorize gas for 32 homes for a month.

 Davila says if you smell the odor, “Then you should call us. Step out of the house, don’t use the telephone inside the house when you smell gas. Don’t turn the lights on. Nothing that would trigger a spark.” 

Last month, more than 400 gas leaks were called in; CPS is required to investigate them all.

Lastly, Davila reminds residents to call 811 before you dig. Gas pipes could be as shallow as twelve inches below ground.