A North Carolina firefighter saved dozens from carbon monoxide (CO) poisoning after he noticed restaurant patrons exhibiting symptoms of the deadly condition.

Lonnie Wimmer was off-duty and attending a 30th birthday party at the Winston-Salem area River Ridge Taphouse Saturday when he noticed people were “acting a little weird.”

“People were starting to act a little weird,” he said, having been trained to spot the signs of CO poisoning. “Heads hurting, people holding their belly, going to the bathroom a lot.”

Acting quickly, he called his “office” at the Lewisville Fire Department, prompting 12 of his comrades to arrive on the scene. When they arrived, they found the CO levels in the eatery were over five times the healthy level.

“We identified the most likely source to be a natural gas heating system,” said Lewisville Fire Department Assistant Chief Steve Williams.