Health & Wellness

The visitor no one wants

Janet Moje
The visitor no one wants

Each year, 50 Canadians die and 132 Canadians are hospitalized for carbon monoxide poisoning. Will you be one of them? We can protect ourselves by knowing the facts.

Carbon monoxide poisoning can happen in two ways… quick or slow. If there is a large amount of CO in an enclosed space, its effects are fast. But if there is a small amount present, it can affect you slowly over time. It’s not just about dying in your sleep, we need to recognize the symptoms.

Health Canada’s Water and Air Quality Bureau biologist, Francis Lavoie, explains, “Whenever you burn something whether it’s wood, natural gas, oil, paper or propane, there’s CO produced.”

Carbon monoxide is a naturally occurring, short-lived gas that oxidizes into the harmless carbon dioxide (CO2) gas and ozone over the course of 1-2 months. In closed environments however, the concentration can easily rise to lethal levels. Without adequate venting, you breathe it in and it replaces the oxygen in your blood, thus reducing the amount of oxygen reaching your heart, brain and other vital organs.

The visitor no one wants

Symptoms are flu-like (minus a fever) with headaches, shortness of breath, impaired motor functions and muscle weakness being the first signs. If higher levels of CO persist, you will experience dizziness, chest pain, poor vision, and eventually coma and death.

It is called the “Silent Killer” - an odorless, colourless gas slightly denser than oxygen. You can’t see it, you can’t smell it, and aside from a CO detector/alarm, you don’t know if it’s around you. It can enter your home any time of the year, but spikes in winter because we burn more fuels to keep warm. It is important to check and clear all vents from any obstructions before you start burning fuels in your home.

What we can do:

  • Clean all fuel vents before the winter season begins.
  • Check vent openings after a heavy snowfall to make sure they aren’t blocked.
  • If you experience symptoms of CO poisoning, go out into the fresh air. If they subside, you can suspect your home has unsafe levels of CO.
  • Watch your pets. CO affects them before it affects us. If they become irritable or vomit, or don’t want to come back into the house, your home may have unsafe levels of CO.
  • Buy a CO detector/alarm, test it regularly to confirm it is working. CO detectors do have an end-life and will start beeping regularly (chirp) despite a battery change when they no longer function adequately. It is now mandatory to have a CO alarm in Ontario, Manitoba, Quebec and the Yukon.
  • If your CO alarm goes off, treat it like a fire alarm. Evacuate immediately and call 9-1-1. If your home is unsafe, do not go back inside until it has been deemed safe.
  • Do not idle your vehicle in a garage - especially if it is attached to your home.
  • Never warm up your kitchen by opening the oven door of a gas appliance.
The visitor no one wants



0.1 ppmv

Natural atmosphere level

0.5–5 ppmv

Average level in homes

5–15 ppmv

Near-properly adjusted gas stoves in homes, modern vehicle exhaust emissions

<1000 ppmv

Car exhaust fumes after passing through catalytic converter

5,000 ppmv

Exhaust from a home wood fire

30,000–100,000 ppmv

Undiluted warm car exhaust without a catalytic converter