Carbon Monoxide and CO alarms for your Home


What is Carbon Monoxide ?

Carbon monoxide (CO) is a colourless, odourless, toxic gas that is produced whenever fuels are burned incompletely, including natural gas, propane, wood, tobacco and gasoline. Carbon monoxide interferes with the body's ability to transport oxygen through the blood to the body's cells. When you breathe in carbon monoxide, it builds up quickly and combines with the blood to produce 'carboxyhemoglobin' (COHb), which reduces the ability of blood to carry oxygen. Carbon monoxide poisoning is the leading cause of accidental poisoning deaths in North America.

How is Carbon Monoxide generated in the home?

Many homes in Canada have gas fired appliances such as a furnace, a boiler, gas fireplace, or a water heater. In most homes, these appliances burn Natural Gas which actually is about 85%-90% methane (CH4). During combustion, the natural gas (methane) is combined with an adequate supply of air (combustion air), where heat and a series of by-products are produced. The by-products are produced because the combustion is never complete (or perfect). Combustion exhaust gases will contain both unburned carbon (soot) and carbon compounds (CO and others). The formula for incomplete combustion in a gas fired furnace is: CH4 + 3O2 = Heat + 2H2O + CO (+/- O2). Other gasses are also produced because the methane is not pure and the combustion air is not pure O2. 

A properly designed and functioning gas fired appliance will have a sealed exhaust vent that expels the exhaust gasses out of the home through a chimney or some other similar type vent. What often happens, though, is that the exhaust gasses are prevented from fully escaping the home and they flood into the living area instead. Depending on the level of concentration of the exhaust gasses inside the home varying degrees of carbon monoxide poisoning can affect the occupants.

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 severe cases, CO poisoning can cause brain damage and death. The elderly, children and people with heart or respiratory conditions may be particularly sensitive to CO. It can poison the body quickly in high concentrations, or slowly over long periods of time.

How can I protect myself and my family from CO poisoning?

The first step to take in prevention is to ensure that all combustion gasses are properly vented to the outside.

  • Have your furnace and your water heater and your gas fireplace serviced annually by a qualified, reputable and licensed technician, 
  • Replace your forced-air furnace filter at least once every year and check it monthly to ensure it is clean and functioning properly,
  • Know the location on the outside of your house where the combustion air vent grill is for every fuel-fired appliance and ensure that they are clean and unobstructed,
  • Don't restrict airflow to your furnace or water heater by storing personal items up against it, or enclosing it into a confined space like a closet,
  • Check your chimney at least once or twice per year to ensure that everything looks fine and the chimney cap is not blocked, or broken, or rusting, or crumbling, etc.,
  • Keep your chimney clean. Open the hatch at the bottom of the chimney to remove the ashes.  Hire a chimney sweep annually.
  • Never leave a car running in an attached garage, even with the garage door open.

The next step to take is to install CO alarms in your home in the appropriate locations and test them regularly to ensure they are functioning properly.

How do CO alarms work?

A carbon monoxide alarm (sometimes called a carbon monoxide detector) is a small electronic alarm that sounds when potentially life-threatening levels of carbon monoxide are present. Models marked CAN/CSA-6.19-01 meet the current Canadian safety standards for carbon monoxide alarms. CO alarms monitor airborne concentration levels (parts per million) of CO over time, and sound an alarm when harmful levels are present. They are designed to sense low CO concentrations over a long period of time as well as high concentrations over a short period of time.

How expensive are CO alarms?

CO alarms range in price from approximately $26 to over $100 depending on whether they are hard-wired, battery operated or plug-in and whether they have additional features (i.e. battery back-up, digital display, etc.). The average mid-range plug-in/battery back-up model is between $35 and $40 per unit.

What about CO Alarm Location?

CO alarms can be used to monitor exposure levels in the following locations:

  • Within 10 feet of each bedroom door and near all sleeping areas where it can wake sleepers,
  • Every home should have at least one carbon monoxide detector for each floor of the home, and within hearing distance of each sleeping area, including the basement,
  • Near or over any attached garage,
  • Near, but not directly above, combustion appliances, such as furnaces, water heaters, and fireplaces, and in the garage,
  • On the ceiling in the same room as permanently installed fuel-burning appliances, and in every HVAC zone of the building,

Where not to locate CO alarms:

  • Directly above or beside fuel-burning appliances, as appliances may emit a small amount of carbon monoxide upon start-up,
  • Within 15 feet of heating and cooking appliances,
  • In or near very humid areas, such as bathrooms,
  • Within 5 feet of kitchen stoves and ovens,
  • Near locations where household chemicals and bleach are stored,
  • In any extremely dusty, dirty, humid, or greasy areas,
  • In direct sunlight, or in areas subjected to temperature extremes.(i,e.-unconditioned crawlspaces, unfinished attics, uninsulated or poorly insulated ceilings, porches,
  • In areas where blowing air may prevent carbon monoxide from reaching the CO sensors.

How long do CO alarms last?

Carbon monoxide alarms have a limited life, typically 5 to 7 years (some even less). Most people don’t realize they need to be replaced this often. Many manufacturers will state the limited life span somewhere in their manual; however, it’s usually not prominent.  The presence of a CO alarm may give you a false sense of security. It could even lead to unsafe combustion practices, thinking that if the air becomes poisonous, the alarm will warn you. Check the manufacturer’s instructions. If your CO detector was put into use before 2010, it needs to be replaced. Your CO alarm may give no indication that it’s no longer functional. Pushing the test button (usually) only tests the battery, horn and circuitry. The test button does not test whether the gas sensing element is still functional.

At what height should CO alarms be installed?

Unlike smoke, which rises to the ceiling, CO mixes with air. Hence CO alarms may be installed at any height. However, if a combination smoke/CO alarm is used, it must be installed on or near the ceiling as per manufacturer’s instructions, to ensure that it can detect smoke effectively.

CO Alarms Now Mandatory in the BC Building Code

The BC Building code has adopted requirements for carbon monoxide alarms in new and renovated residential buildings:

Buildings that contain residential occupancy shall have a carbon monoxide alarm(s) installed in every bedroom or within 5 m of each bedroom door, measured along the corridor, if the suite:

  • contains a fuel-burning appliance,
  • shares a wall/floor or ceiling with a service room that contains a fuel-burning appliance and the service room is not within the suite of residential occupancy. Carbon monoxide alarm is also required in such service room
  • shares a wall/floor/ceiling or adjacent attic or crawl space with a storage garage
  • NOTE: If a fuel-burning appliance, such as a fireplace, is located inside a bedroom the carbon monoxide alarm should be installed within the bedroom.

The carbon monoxide alarms shall:

  • conform to CAN/CSA 6.19, Residential Carbon Monoxide Alarming Devices,
  • be equipped with an integral alarm conforming to CAN/CSA 6.19,
  • be battery-operated or hardwired, and
  • if hardwired, must comply with CEC Rule 32-110, and
  • be mechanically fixed at a height as per manufacturers’ recommendations.
  • plug-in type is not acceptable.

Units combing smoke and carbon monoxide alarms are acceptable.


The City of Vancouver has taken it one step further

Recent City of Vancouver fire bylaw changes have made carbon monoxide alarms mandatory for all residential buildings with fuel-burning appliances or an attached garage. It is the shared responsibility between an owner and a tenant to make sure that there is a carbon monoxide alarm installed in their home. Vancouver is the third jurisdiction in Canada to adopt bylaws making carbon monoxide monitors mandatory.

On a Personal Note

I have been in many homes and inspected many furnaces. In far too many of them I have seen a potentially dangerous/deadly situation. I have advised people of the dangers in no uncertain terms and I just know that many of them are going to do nothing to remedy it. I think it has something to do with the fact that carbon monoxide is invisible and odourless. It differs from smoke and fire. People understand the dangers of smoke inhalation and house fires. They’re obvious. We have all seen a building on fire and the smoke they produce and we recognize that we need to protect ourselves from that. But carbon monoxide is different. It really is the silent killer. Even if it doesn't kill you it may make you sick and you won’t even know why. It seems people think, ‘everything’s been fine so far, what’s the worry?’ 

In Canada, 380 accidental deaths were caused by CO poisoning between 2000 and 2009 and there are untold thousands of CO poisoning related illnesses. That's over 3 deaths every month! Many experts believe that CO poisoning statistics are an understated problem because the symptoms of CO poisoning mimic a range of common health ailments. It is likely that a large number of mild to mid-level exposures are never identified, diagnosed, or accounted for in any way in carbon monoxide statistics. Most CO exposures occur during the winter months, especially in December and January.

This winter, check the date on your CO alarm. If it is older than 5 years, replace it. If you don't have them in your home, install them. In Vancouver, it’s the law. Make sure you have enough CO alarms in your home to offer proper protection and check them often. Have your furnace and water heater professionally serviced. Clean your chimney or have it professionally swept. Be aware of the potential risks and be on the look out for their signs.