Ontario's provincial government is considering making carbon monoxide detectors mandatory following two high-profile poisonings in which the detectors were absent.

"... I'm quite prepared to ask our officials to see what options are available to require a carbon monoxide detector," Municipal Affairs Minister Jim Watson told CTV Toronto on Wednesday.

Progressive Conservative MPP Ernie Hardeman, a firefighter for 25 years, urged the government to move quickly on such a law, saying people can become complacent if they think their homes heating system is in good repair.

"I don't think there's many families in Ontario that would not be prepared to pay up the small cost it would take to put detectors in their home, providing they knew the risks of not doing it," he said.

The province did require carbon monoxide to be installed in new homes starting in 2002, but didn't require them in existing homes.

"Carbon monoxide can't be smelled, seen or tasted," Capt. Mike Strapko of Toronto Fire Services said Wednesday. "The only way to know is with the device."

Some Ontarians have learned that lesson the hard way recently.

Two people, a Toronto mother and her 18-year-old son, are recovering in hospital after inhaling the deadly  fumes in their west-end home.

Emergency services were called to 110 MacDonald Ave. in the Jane and Lawrence area around 9 p.m. Tuesday. There, they found two unconscious victims in the basement of the home. Another family, including two children, living on the upper level of the same home were also suffering from carbon monoxide poisoning.

Three ambulances rushed the two families to Toronto-area hospitals. A semi-conscious pet dog was also treated for gas poisoning, Strapko told ctvtoronto.ca.

All but one of the victims was taken to Humber River Regional Hospital. A female patient was taken to Toronto General where she was placed in a hyperbaric chamber -- a high-pressure oxygen therapy chamber used to treat patients in severe need of an additional air supply for breathing.

"It floods the blood with oxygen to get the carbon monoxide out," Strapko said.

Phuong Nguyen, the woman who lives on the upper level of the home, and her two kids, ages 11 and 9, were treated and released from hospital at about 2 a.m. Wednesday.

Nguyen stopped by the MacDonald Avenue home briefly on Wednesday afternoon to pick up some essentials for herself and the children. They'll be spending the night at her sister's home.

"Yeah, I was scared," Nguyen told CTV Toronto on Wednesday, adding she worried for her kids.

The night before, her head was hurting, her hands shook and her heart was beating quickly, she said.

Nguyen said 9-1-1 was called shortly after one very ill teen victim knocked on her door upstairs. "He was shaking," she said.

An 11-year-old boy placed the 9-1-1 call, Strapko said.

The home was not equipped with a carbon monoxide detector, investigators said.

The house still isn't safe to occupy as investigators attempt to pinpoint the leak's cause.

The incident happened the same day an OPP officer from Woodstock, Ont. lost her week-long battle for survival. Const. Laurie Hawkins was suffering from carbon monoxide poisoning after a gas leak killed her husband, 14-year-old daughter and 12-year-old son.

A buildup of gas in a fireplace pump appears to have caused the toxic leak in their Woodstock home on Dec. 1.

There was no carbon monoxide detector in the home.

With reports from CTV Toronto's Paul Bliss and Zuraidah Alman