Barrie's fire department is warning the public after receiving a rash of calls involving carbon monoxide.

Firefighters have been busy in February responding to 23 calls involving CO alarms going off.  Emergency crews say people are trying to stay warm and they're using gas fire places, wood stoves and sometimes warming cars up in the garage.

“All of those devices produce carbon monoxide and in large volumes,” says Jeff Weber, Barrie’s deputy fire chief. “So with our houses all closed up tight, snow against fences, snow against the house, snow against our exhaust pipes, we end up with more opportunity for CO to build up in our house.”

One of those calls came from Monique Gadd. Last week her furnace started leaking, and carbon monoxide was slowly seeping into the home. It was enough to set off one of the three CO detectors in the house.

“It's not something you can smell, or see and it is a silent killer. You could be here reporting on a different note, reporting a different story,” says Gadd. “It could have been a different outcome if it we didn't follow our gut and call the fire department.”

In fact, the family called the Barrie fire department not even knowing the gas was starting to build up. Emergency crews arrived and discovered the problem.

Some of the calls reported to firefighters involved a problem with the alarm, but on four of those calls, crews detected the deadly gas.

Firefighters say people sometimes confuse the symptoms of carbon monoxide exposure with the flu. The gas can make you dizzy, nauseous and bring on headaches.

The best way to tell if it's something more serious is by coupling those symptoms with a detector. If the CO alarm is producing a reading, people are urged to contact emergency services.

CO detectors will be mandatory is most Ontario homes by April.