Dive summary:

• A Montana energy company manufactured scratch-and-sniff cards that smelled like natural gas and yesterday one of the crates of 25,000 expired cards got hauled away by a garbage truck, creating a smell scare across the city.
• Several buildings in downtown Great Falls, Mont. were evacuated after residents along the waste haulers route complained something smelled like leaking gas.'
• When the cards were compacted by the truck it essentially acted as a giant finger that triggered all of the cards to release the smell.

From the article:

Nick Bohr, general manager at Energy West, said workers at the company were cleaning out some storage areas and discarded several boxes of scratch-and-sniff cards that it sent out to customers in the past to educate them on what natural gas smells like.

“They were expired, and they were old,” Bohr said. “They threw them into the Dumpsters.”

When the cards were picked up by sanitation trucks and crushed, “It was the same as if they had scratched them.” ...