A sour gas odor reported across northwest Kalispell on Thursday morning turned out not to be as dangerous as people may have thought — although it was just as smelly.

NorthWestern Energy spokesman Butch Larcombe said the company had brought in some old gas pipe from a nearby rural area to the firm’s North Meridian Road location earlier that morning. Attached to the pipe was a pressurized odorant pot containing mercaptan.

Mercaptan is a sulfur-containing compound used to give natural gas its trademark odor, since the gas itself is odorless. Similar compounds occur naturally in rotten eggs, onions and garlic and in skunks’ spray.

The addition of mercaptan to natural gas lines makes it possible to smell a gas leak, warning anyone nearby of the danger.

However, the odorant pot was leaking, and while the pipes were in the NorthWestern Energy welding shop, some of it spilled. Concentrated mercaptan has an extremely strong odor, and when employees opened the doors to let the smell out of the shop, it began to spread quickly.

The sudden smell led to several calls to police as well as NorthWestern Energy, including a call from Kalispell Middle School, Larcombe said. NorthWestern Energy received about 10 calls, while the Kalispell Police Department and Kalispell Fire Department also received calls.

“Apparently it was able to be smelled somewhere between a quarter- and half-mile radius,” Larcombe said. “Mercaptan does its job very well.”

A northerly wind carried the smell as far as Windward Way, where a mental health facility temporarily evacuated due to concerns of a gas leak.

Kalispell firefighters responded to try to help seal in the smell by placing the leaking container in a larger plastic container, but then discovered the mercaptan container was pressurized and firefighters didn’t want to accidentally create a pressure bomb.

Instead, NorthWestern Energy employees from a larger operation in Cut Bank were dispatched with a neutralizing agent that would eliminate the odor entirely. They were expected to arrive in Kalispell around 2 p.m. By that time, mother nature had intervened slightly with wind that helped dissipate the smell.

Larcombe noted that while there was no gas leak and no danger, people did the right thing by calling the company and reporting the odor.

He said he was unaware of the situation occurring previously at NorthWestern Energy, but a similar incident once happened in Great Falls involving a gas company there.