DENVER — Multiple Denver metro area agencies were investigating reports of widespread natural gas or sewage odors Sunday morning.
People across Douglas County, Aurora, Denver and other parts of the area woke up to the smell.
Xcel said in a statement that it received several calls about the odor, but that its natural gas system is working with no known leaks or line breaks, and that crews believe the smell is "sewer related."
The agencies said there is no need to call 911 for the outside odor, unless a gas leak or hissing sound can be heard.
South Metro Fire Rescue said that a temperature inversion caused by the Arctic cold front moving through Colorado could be the reason the smell was lingering outside.
A temperature inversion is when the air temperature of a layer in the atmosphere is cooled by contacting a colder surface, causing the air mass to be colder towards the bottom and warmer towards the top.
"Sometimes on cold mornings this happens," the department said. "Natural gas meters are designed to burp small amounts of gas to regulate pressure and usually that vapor dissipates quickly in the atmosphere."
South Metro said that natural gas is inherently colorless and odorless, so a mercaptan is added so that a "rotten egg" smell can be noticed when there is a leak. When there is a temperature inversion, the mercaptan odor can get trapped near the ground and linger.
Devin Parkes woke up to that foul odor inside his home. He said the entire area around the Highlands Ranch neighborhood reeked.
“Kind of like rotten eggs,” he said. “Sour. It just smelled sour. It was very pungent and concerning.”
Worried that it was a gas leak, Parkes evacuated his family from the home.
“We assumed it was either a gas leak or a sewer problem, but the gas leak was our main concern,” Parkes said.
With the cold weather sticking around Sunday night, there's a chance the smell could return Monday.
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