A carbon monoxide leak led to the evacuation of a northwest Calgary building on Friday.
Firefighters were called to the 6800 block of Centre Street N.W. at 12:15 p.m.
"When we arrived, CO levels were quite high, spiking, actually, maxing out our monitors at 1,000 parts per million," CFD district chief Dave Nelson said.
In total, 35 people had to leave the building and were temporarily sheltered at a nearby fire hall.
Later on, Calgary Transit buses were brought in to keep them warm.
Four people – two adults and two children – were taken to hospital in stable condition.
Nelson says the carbon monoxide leak occurred when a fresh air intake was blocked with ice.
"Make sure you're checking your intakes and your exhaust for your furnaces and that kind of stuff, to make sure that you have fresh air coming in, as well as fresh air able to escape."
He said they were alerted when a carbon monoxide detector in another unit of the building went off.
"It's a good reminder to make sure you have CO detectors," Nelson said. "A lot of homes don't have CO detectors."
Crews remained at the scene for a few hours to ventilate the building and make sure it was safe for residents to return inside.
