A Dartmouth family is warning others about the dangers of carbon monoxide poisoning after a close call last month.

Reza Kashiloo and seven members of his family were sleeping the morning of March 18 when deadly levels of the gas started building up in their home.

Their ADT alarm system activated, alerting a dispatcher in Calgary who called emergency crews in Halifax.

"They stayed with us until the levels were down to safe level before they left and at that point I realized that it was a really close call," Kashiloo said.

Firefighters determined an outside boiler vent had been covered with snow, causing the carbon monoxide levels to elevate in the home.

High levels of the odourless gas can be fatal within minutes.

“It’s especially dangerous if you’re already asleep, and likely you’re not going to wake up and come out of it, unless something wakes you up,” said Halifax Deputy Fire Chief Roy Hollett.

On Friday, the family and alarm company thanked the Halifax fire department for their quick response.

The company presented the department with a $5,000 grant to provide smoke and carbon monoxide detectors to residents in need.

“It’s a program that we have for anyone who is unable to provide a smoke detector for their house. For us, not having one is not an excuse,” Hollett said.

Kashiloo said he hopes his family’s close call will convince others to install their own carbon monoxide detectors.

With files from CTV Atlantic’s Sarah Ritchie