Two parents and two boys have arrived back home from an Ottawa hospital Friday after suffering from carbon-monoxide poisoning at their Gatineau, Que., home.

Gatineau firefighters, paramedics and police were called at about 4:30 a.m. Friday about a gas leak at 56 Jeanne D'Arc St.

Once they arrived, firefighters said, they found all four family members conscious but with headaches.

The four were treated with breathing apparatus and transferred to the Ottawa Hospital in critical condition. They were treated with a hyperbaric chamber, which supplies high-pressure oxygen therapy.

Jeffrey Tanguay said he and his family were lucky they got out of the house when they did.

"We got out apparently in the nick of time," he said. "We had no idea until we got to the hospital, and they were telling us our carbon monoxide levels were at 30 something per cent, and apparently you aren't supposed to wake up if they are over that. So we're just lucky that my wife got up and we all up and got out."

At first, they had thought his wife was just feeling unwell, Tanguay said. It wasn't until their second boy came up to them, throwing up, that they suspected something else was wrong.

Gatineau firefighters said they and the gas company will meet the family to go over safety precautions for the house.

CO levels much higher than normal

Fire Chief Luc Meilleur had earlier told CBC News that two family members were found unconscious and that a carbon monoxide reading showed 873 parts per million. The normal PPM is about 10.

But Gatineau Fire's Richard Groulx later corrected that, saying there was a reading of about 300 PPM. There was no carbon-monoxide detector in the home.

Paramedics were also exposed to the carbon monoxide for about 30 minutes, Meilleur said, and they were advised to go to the hospital.

Firefighters believe the carbon-monoxide leak originated in the furnace.