An apartment building in Airdrie, Alta., was evacuated for the second time in one week due to elevated carbon monoxide levels, after a child died from exposure to the toxic gas on Sunday.

The fire department was called to 700 Willow Brook Rd. shortly after midnight on Friday, after a CO detector went off in one of the units on the ground floor.

The condo management company told residents via email that the evacuation was lifted at 3:30 a.m., once the CO was cleared, and that the gas to the impacted unit will remain off until the issue has been fixed.

The detector had been supplied to the resident by the Airdrie Fire Department after a fatal incident on Sunday, when a water heater failed to ventilate properly and a 12-year-old boy died.

"Right away we realized it was another carbon monoxide issue," said Sarah Gillespie, who lives in one of the units.

The incident on Friday was also caused by an on-demand heater that didn't ventilate correctly, but this time, no one was hurt.

"I think everyone's pretty on edge right now, not sure what to do. These are our homes, but we're not feeling really safe at this point," Gillespie added.

Sarah Gillespie says she's concerned, after her apartment building was evacuated twice in one week due to CO leaks. (CBC)

Airdrie fire chief Garth Rabel said 67 CO detectors were given out to occupants on Sunday, and another 10 were handed out Friday.

He said that, while he couldn't speak to whether or not the same supplier installed all of the units in the building, it would be a good idea for residents to have their heaters inspected.

"Well, it would be prudent for the owners of those apartments to have a qualified, certified technician to come in and inspect and service if required those units," Rabel said.

He said that the resident's insurance company will be further investigating the unit that malfunctioned on Friday.

This week wasn't the first time the Airdrie complex has dealt with heightened CO levels.

In 2014, the fire department was called out for the same reason.

In the wake of the incident, friends of the deceased 12-year-old child's family have started a petition to make carbon monoxide detectors mandatory for all Alberta homes.

Gillespie told CBC that she's had ATCO Gas come in to inspect her unit, but she's still concerned.

"It's so tough. This is my home, and I love my place, but you want to feel safe and secure," she said.