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As we turn on our furnaces for the Fall and Winter, it’s time to think about the potential threat posed by carbon monoxide.

What is Carbon Monoxide?

Carbon monoxide (chemical symbol: CO) is a colourless, odourless gas that is formed by incomplete combustion of fuels such as wood, charcoal and natural gas. It is toxic because, when it enters our bloodstream, it robs the blood of its ability to carry oxygen to our organs and muscles.

How is it formed?

Most of us associate carbon monoxide with automobile exhaust, but that’s not the only source.

Carbon monoxide is formed by incomplete combustion of wood, charcoal or natural gas. Improperly ventilated appliances and engines, particularly in a tightly sealed or enclosed space, may allow carbon monoxide to accumulate to dangerous levels.

Your furnace, water heater, stove, space heaters, fireplace, woodstove, charcoal grill, and dryer can be sources of CO, especially if they are gas-powered, not in good working condition or have been installed without proper ventilation.

Vehicle exhaust fumes from attached garages also can become CO hazards – even if the garage door is open.

Using kerosene heaters or charcoal grills indoors, or running a car in a garage can cause CO levels to rise high enough to result in death or serious illness.

More modern housing construction techniques have made carbon monoxide even more of a threat. Doors and windows in homes are more tightly sealed to prevent drafts from the outside. But this also reduces the amount of fresh air – and oxygen – entering your house. It’s especially a problem in winter, when we have windows closed for the season.

Your home

• Never use a cooking device—an oven, grill, or camp stove—to heat your home.
• If you have a wood-burning fireplace, always make sure the damper is open when the fire is going, to allow CO to go up the chimney with other combustion products. When you put out your fire, make sure it is out, with no active coals. And leave the damper open for a while after putting the fire out to ensure CO doesn’t stay in the house.
• If you have a fireplace, have your chimney cleaned every few years. Blocked flues keep CO from escaping your home and buildup of creosote (a tarry byproduct of burning wood) can cause chimney fires.
• Install a carbon monoxide alarm on each level of your home as your first line of defense. CO detectors are most effective when used in conjunction with preventive maintenance.
• Replace old or faulty central heating and air conditioning units with new and improved models.
• Make sure any heating and air conditioning system is installed by trained professionals with proper ventilation.
• Maintain your heating and air conditioning system regularly, usually just before each big change of season.

Your garage

• It might seem like a time-saver to run your car in the garage before a long commute, especially on a cold winter’s morning. But the emissions from your vehicle can fill your garage with carbon monoxide even if the garage door is open.
• Always back your car out of the garage to let it warm up. Never leave it running in the confined space of a garage, particularly if the garage is attached to the home.
• Never run lawnmowers, snowblowers, generators or other gas-powered engines in confined areas like garages or sheds.

Your car

• Never dismiss a fender bender as something you’ll get checked later. Get your exhaust system checked by a mechanic right away. Even minor collisions can cause breaks in your car’s exhaust system, allowing CO to enter into your passenger area.
• If you get stuck in deep snow by the side of the road and decide to stay in your car and keep warm with your engine running, be sure to clear snow away from your exhaust pipe. A blocked exhaust pipe can cause CO to back up into your passenger area.

Preventing Carbon Monoxide Poisoning

Carbon monoxide detectors are the fastest way to prevent CO poisoning. You can install a carbon monoxide detector (or multiple detectors) in your home. They work much like your fire or smoke alarm by sounding a siren when they detect carbon monoxide.

How do carbon monoxide detectors work?

Carbon monoxide detectors sound an alarm when they sense a certain amount of carbon monoxide over time. Different sensors set off different types of alerts.

• Biomimetic sensor: a gel changes color when it absorbs CO, and this color change triggers the alarm.
• Metal oxide semiconductor: When the silica chip’s circuitry detects CO, it lowers the electrical resistance, and this change triggers the alarm.
• Electrochemical sensor: Electrodes in a chemical solution sense changes in electrical currents when they come into contact with CO, and this change triggers the alarm.

When will my carbon monoxide detector go off?

The CO alarm sounds if your sensor detects a buildup of carbon monoxide in your home—usually before you start sensing symptoms. At lower concentrations (50 ppm), it may take up to eight hours for the alarm to go off. Higher levels (over 150 ppm) can trigger an alarm within minutes.

Act quickly when an alarm sounds because low doses over long periods can be just as dangerous as sudden exposure to carbon monoxide in ultra-high doses.

How Much CO Does It Take to Make Me Feel Sick?

Most people begin to feel the effects of carbon monoxide exposure at 70 ppm. This is why it’s important to have CO detectors since lower levels don’t bring obvious symptoms.

What kind of carbon monoxide detector should I get?

Overall, carbon monoxide detectors sense CO fast and alert you as soon as they do. But there’s a surprising amount of variety in today’s carbon monoxide sensors.

Some simple models plug into outlets or use a battery and alert you with a loud siren, like the one on your smoke detector. These models are cheap and suitable for multi-room buildings that need several units spread throughout.

Many models include sensors for both smoke and carbon monoxide. These are an easy option that you can swap out your existing smoke detectors for. They also reduce the number of sensors on your walls or ceilings.

You can also find smart models that connect with your home security system or alert you of danger through a mobile app. These models are expensive but can be a wise investment if you want extra safety for kids and pets at home.

Sensor Maintenance

No matter what type of carbon monoxide detection you have, it’s a good idea to conduct regular maintenance:

• Test it frequently using the button on the front (once a month).⁵
• Replace the batteries as often as the instructions recommend.
• If you have a wired sensor with a battery back-up, make sure both power sources are working.
• Replace the sensor every few years according to manufacturer guidelines (these sensors don’t last forever).

Where should I place a carbon monoxide detector?

Ensure everyone in the house can hear when an alarm goes off by placing a CO sensor in or near each of four critical locations in your home:

1. At least one on each level – especially in the basement, where your furnace is located.
2. Near each bedroom or sleeping space
3. By doors that lead to attached garages
4. In your garage – whether attached or not.

Bottom Line

Christine Mercado, who is the Chair of the LBNA, is also a Captain in the City of Vaughan Fire and Rescue Service and has some good advice. “Keeping your smoke and CO detectors in good working order are key to safety in the home. But don’t forget to plan and practice your escape route if your detectors go into alarm mode”

Learn More

The City of Toronto has an excellent web page about carbon monoxide detectors and the regulations associated with them.

If you are a landlord, you should check out this page because the Ontario Fire Code has specific regulations about having CO detectors in your rental property. There are fines up to $50,000 for an individual owner and $100,000 for a corporation.

If you are a tenant, visit the City’s web page to ensure your landlord has adequately provided for your safety.