Kenai, a 14-year-old Bernese mountain dog mix, began barking at 4 a.m. on Sunday, as Kirstin Kraig and her family and friends enjoyed a near-tragic getaway weekend in New Castle on the Western Slope, according to The Denver Post.

The group had cooked pizza in a propane oven the evening before, and during the night dangerous carbon monoxide gas built up. They were later jarred awake by Kenai’s persistent barking and whining, and, feeling woozy, soon recognized the problem, in part owing to widespread media attention about carbon monoxide poisoning in recent months.

Two of the people were in such bad shape they had to be evacuated via helicopter and treated in a hyperbaric chamber at Presbyterian/St. Luke’s Medical Center in Denver, where they recovered. “I truly believe that if it weren’t for Kenai, we wouldn’t all be here today,” Kraig says.