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Carbon Monoxide Alarms

Carbon Monoxide (CO) is a poisonous gas that you cannot see, smell or taste. It is often referred to as the “silent killer.” CO is produced by the incomplete burning of fuels such as natural gas, propane, heating oil, kerosene, coal, charcoal or wood.

Carbon Monoxide (CO) alarm will alert you when dangerous levels of CO are inside your home. A working alarm will ring loudly giving you the and your family the early warning you need to get out. CO alarms can warn you about sudden failures of fuel-burning appliances and are a good first line of defence against CO exposure.

Types of CO Alarms

There are different types of alarms with different features, so choosing the right one can be confusing. Take comfort in knowing that while alarms might look different and/or have different features, they are all tested to the same standard. Make sure that the alarm you are purchasing is CSA-6.19 Residential Carbon Monoxide Alarming Devices or UL 2034 Single and Multiple Station Carbon Monoxide alarms. Features to consider:

  • Power Source
    CO alarms can be electrically powered, battery-powered, electrical plugin or a combination. If you are installing a plugin type or electrically wired alarm, a battery backup is recommended in case of power failures.
  • Digital Display
    A digital display shows the parts per million (PPM) of CO that is in your home. Alarms aren't activated unless levels reach 70 PPM, however a digital readout gives you an opportunity to have fuel-fired equipment inspected and repaired prior to an emergency occurring.

Where to Install CO Alarms


Unlike smoke, CO mixes freely with the air, so your CO alarm doesn't have to go on the ceiling or up high. It does need to be near the area where you sleep so that it is loud enough to wake you up and get you into action. If your home has a fuel-burning appliance or an attached garage, install a carbon monoxide alarm adjacent to each sleeping area. Read the manufacturer’s instructions carefully and follow them exactly.


If you live in an apartment or condo building and there is a fuel-burning appliance inside your unit, install a carbon monoxide alarm adjacent to your sleeping area. Read the manufacturer’s instructions carefully and follow them exactly.

If the building has a service room with a fuel-burning appliance, CO alarms must be installed in the service room and adjacent to each sleeping area of all condos/apartment/units above, below and beside the service room.

If the building has a garage, CO alarms must be installed adjacent to each sleeping area of all condos/apartment/units above, below and beside the service room.

Replacing Carbon Monoxide Alarms

Read the manufacturer’s instructions carefully and follow them exactly. Carbon monoxide alarms do not last forever. Check the expiry date on the alarm so that you know when to replace them. If you cannot find a date, replace the alarm. 

Frequently Asked Questions

What are the symptoms of CO poisoning?

Exposure to CO can cause flu like symptoms such as headaches, nausea, dizziness, burning eyes, confusion, drowsiness and even loss of consciousness. In very severe cases, CO poisoning can cause brain damage and death. The elderly, children, people with heart or respiratory conditions, and pets may be particularly sensitive to CO and may feel the effects sooner. If you experience flu-like symptoms at home but feel better when you leave, it might be a warning that there is a CO leak inside your home.

What can create a CO hazard?
  • Fuel-burning appliances, venting systems and chimneys that have not been serviced or maintained regularly by a qualified service technician or heating contractor.
  • A chimney blocked by a bird or squirrel's nest, snow and ice or other debris.
  • Improper venting of a furnace and cracked furnace heat exchangers.
  • Exhaust fumes seeping into your home from a car, lawn mower, or snow blower running in an attached garage.
  • Using fuel-burning appliances designed for outdoor use (barbecues, lanterns, chainsaws, lawnmowers, snow blowers) in a closed area (tent, recreational vehicle, cottage workshop, garage).
  • Combustion gases spilling into a home if too much air is being consumed by a fireplace or exhausted by kitchen/bathroom fans in a tightly-sealed house.
What can I do to prevent a CO hazard?
  1. Get an annual inspection of all fuel-burning appliances, venting systems and chimneys, by a qualified service technician. Regularly maintained appliances that are properly ventilated should not produce hazardous levels of carbon monoxide.
  2. Install and regularly test CSA approved carbon monoxide alarms.
  3. Trust your CO alarm. If it activates or the digital readout shows a number other than 0, have a professional in to check out your home. Alarms are rarely faulty.
What should I do if I suspect CO in my home?

If you or anyone else in your home is experiencing the symptoms of CO poisoning, or your CO alarm sounds, make sure that everyone leaves the home immediately and gets medical help. Call 911. Leave your doors and windows closed when you leave so that Emergency Personnel can get an accurate reading of the CO levels in your home when they respond.

I’ve heard both stories: CO is lighter than air, so the alarm(s) must go on the ceiling; CO is heavier than air and alarms must be kept at floor level. What is true?

CO is virtually the same weight as air, so it does not concentrate high or low. It closely resembles the behaviour of food colouring in water; it will eventually mix evenly throughout, no matter the size of the container.

Is it a false alarm when my carbon monoxide alarm sounds and there doesn't seem to be a problem?

A false alarm should not occur if your alarm is in working order. Remember, carbon monoxide is an odourless, colourless gas. If your carbon monoxide alarm went off, it detected potentially harmful amounts of carbon monoxide. After the professionals have evaluated the situation, make sure no one has any symptoms of carbon monoxide poisoning. Here are a few situations that may cause a carbon monoxide alarm "false alarm":
• The carbon monoxide alarm needs to be relocated. Carbon monoxide alarms should be located 15-20 feet away from all fossil fuel burning sources like furnaces and stoves. Alarms should be located 10 feet away from sources of humidity like showers.
•  Fossil fuel burning appliances may not be burning fuel completely. Check pilot lights/flames for blue color. Appearance of yellow or orange flames indicates incomplete combustion-a source of carbon monoxide.​
•  Some cleaning solvents, humidity, low battery or end of life of the device can also cause the alarm to activate.

Should I keep an alarm right beside the furnace?

No, for several reasons. If the alarm is right at the furnace, then it is probably in the basement where your chance of hearing it is minimised. Secondly, if the alarm sounds at the furnace, most people conclude that the furnace is the problem and may fail to investigate other potential sources. Thirdly, if the furnace is the root of the problem, it’s going to blow CO throughout your home anyway. Install alarms where you are most likely to hear them. Your owner’s manual will identify best options.

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