An apartment building on Cobourg Street in Ottawa got a new furnace and new carbon monoxide detectors Tuesday after a brush with disaster on Sunday night.

A tenant at 179 Cobourg St. near Besserer Street showed up at the Montfort hospital in Ottawa with symptoms that staff suspected might be caused by carbon monoxide poisoning.

Emergency nurse Yan Landry-Bruneau saw her and said she had symptoms of vertigo, she felt nauseous and confused.

Cobourg carbon monoxide scare

Two of the residents at 179 Cobourg required treatment in hospital. (CBC)

Hospital staff had the presence of mind to find out where the woman lived, and asked firefighters to check on other people at the address.

When firefighters arrived at the building, they measured the carbon monoxide levels and found them to be dangerously high in some parts of the building.

All of the tenants of the building were vacated and checked at hospital.

Assistant deputy fire chief Sean Tracey said hospital staff likely prevented a tragedy.

"We say that carbon monoxide is the silent killer. You can't sense it, you can't smell it. You breathe it in, it bonds with your blood, and causes you to breathe faster and take in more carbon monoxide, and very quickly it can lead to fatal conditions," said Tracey.

The technicians replacing the furnace suspect a chimney blockage caused carbon monoxide to leak into the building.

The building superintendent showed up with new carbon monoxide detectors on Tuesday. He said the building already had detectors but, for some reason, they did not work.

The Ontario legislature passed a bill last Thursday requiring carbon monoxide detectors in homes. It's expected to become law after it receives royal assent in January.