Carbon monoxide detector: where it is mandatory and what to do when it goes off

The carbon monoxide detector is officially called a carbon monoxide alarm. That is the term used in Quebec's Code de sécurité and on Québec.ca. The device sounds when the air contains an abnormal level of this gas, which no one can see or smell. When it sounds, the official instruction is to get out, dial 9-1-1 and wait for a firefighter's permission before going back in.

Carbon monoxide and its sources at home

Québec.ca describes carbon monoxide, also called CO, as a toxic gas that cannot be seen or smelled, and that irritates neither the eyes nor the airways. It is released when an appliance or a vehicle burns fuel. The government page, updated on November 23, 2023, names five families of sources.

• Non-electric heating appliances, such as oil furnaces and wood fireplaces
• Vehicles with combustion engines, such as cars and snowmobiles
• Natural gas or propane appliances, such as stoves and water heaters
• Gas-powered tools, such as lawn mowers and generators
• Outdoor appliances, such as barbecues and camp stoves

Poisoning happens when these appliances are defective, poorly maintained or used in an enclosed space, for example a car engine running in a garage, even with the door open.

Which dwellings require the alarm

Section 359 of the Code de sécurité (chapter B-1.1, r. 3), up to date as of June 1, 2026, requires a carbon monoxide alarm in a dwelling that contains one of these two elements.

• A fuel-burning appliance
• Direct access to an indoor parking garage

Section 360 adds that the alarm must comply with the CAN/CSA-6.19 standard, have a built-in alarm and be installed according to the manufacturer's recommendations.

This chapter of the Code does not cover every building. Its section 340 exempts a building used as a dwelling that has no more than 2 storeys or no more than 8 dwellings. In a house, the municipal by-law therefore decides. Québec.ca writes, in a page updated on September 17, 2026, that most municipal by-laws require a carbon monoxide alarm in the home when a garage is attached to the house. The Régie du bâtiment du Québec, Quebec's building authority, recommends a certified alarm in all residential buildings where fuel is used.

This text summarizes public documents. It is not legal advice.

Where to install the alarm

All occupants must hear the alarm when it goes off. Québec.ca, in its page updated on July 29, 2025, recommends installing one in these places.

• On every floor, including the basement
• In the hallway near the bedrooms
• In every bedroom where people sleep with the door closed
• Near the stairs
• Near the door of the garage attached to the house
• In the room above the attached garage

The same page says where not to install it: in the kitchen, in the bathroom, inside the garage and less than 2 metres from a cooking or fuel-burning appliance. It also rules out rooms where the temperature goes above 37.8 °C or below 4.4 °C.

The combined smoke and carbon monoxide device

A smoke alarm does not detect carbon monoxide. The Régie du bâtiment and Health Canada both say so. Some models of carbon monoxide alarms are combined with a smoke alarm. According to Québec.ca, they are installed following the same recommendations as a smoke alarm.

Other models run on batteries or electricity. Québec.ca asks that every alarm meet Canadian standards and carry the ULC logo.

Lifespan and maintenance

None of the official sources consulted sets a lifespan in years for the carbon monoxide alarm. Québec.ca writes that its lifespan is limited and that it should be replaced according to the manufacturer's recommendations. Health Canada advises checking its expiry date. The only published figure concerns batteries: Québec.ca suggests models with lithium batteries, which last 10 years.

Maintenance comes down to two steps: every month, press the test button for a few seconds, and replace the batteries when you hear the intermittent beep.

What to do when the alarm sounds

Québec.ca gives two sets of instructions, depending on whether someone has symptoms or not. If you or someone present has symptoms, whether the alarm sounds or not, here is what to do.

• Leave the premises and go outside
• Dial 9-1-1 or call the Centre antipoison du Québec (Quebec Poison Control Centre) at 1 800 463-5060
• Leave the door open on your way out to air out the place completely
• Wait for a firefighter's permission to go back inside, even for a few minutes

If the alarm sounds and no one has symptoms, shut off the fuel supply if possible, go outside, dial 9-1-1 and leave the door open. Here too, a firefighter authorizes the return.

Symptoms of poisoning

Québec.ca groups the symptoms by the severity of the poisoning and notes that they resemble those of other health problems.

Source: Québec.ca, Intoxication au monoxyde de carbone, updated on November 23, 2023.

The same page states that you must see a doctor to treat carbon monoxide poisoning.

Further reading

• Fire prevention at home: the three devices
• Smoke detector: what the law requires in Quebec
• Fire extinguisher: which one to choose for the home, where to put it and when to refill it
• Loss: definition, reporting it to the insurer and the steps after a fire

Frequently asked questions

Where should a carbon monoxide detector be installed?

Québec.ca recommends an alarm on every floor, including the basement, in the hallway near the bedrooms and near the door of the attached garage. It does not go in the kitchen, in the bathroom or inside the garage.

Is a carbon monoxide detector necessary?

Yes, as soon as there is a source of this gas. Health Canada recommends at least 1 alarm with a backup battery in a home that has fuel-burning appliances.

How can you tell if there is carbon monoxide in a room?

You cannot tell with your senses. Québec.ca specifies that smell is a poor tool for preventing poisoning. Only the alarm signals this gas.

Are carbon monoxide detectors mandatory?

Section 359 of the Code de sécurité requires one in a dwelling that contains a fuel-burning appliance or direct access to an indoor parking garage. A building with no more than 2 storeys or no more than 8 dwellings is exempt: your municipality's by-law applies there.

Will the carbon monoxide detector be mandatory in 2026?

The requirement already exists. Section 359 of the Code de sécurité appears in the text up to date as of June 1, 2026, and it comes from a 2012 order in council. The sources consulted announce no new provincial rule for 2026.

What is the best place to install a carbon monoxide detector?

Health Canada answers that the hallways leading to the bedrooms are the most important places to install one. Québec.ca adds every floor and every bedroom where people sleep with the door closed.

Sources

• LégisQuébec, Code de sécurité, chapter B-1.1, r. 3, sections 340, 359 and 360, up to date as of June 1, 2026
• Gouvernement du Québec, Avertisseurs de monoxyde de carbone, up to date as of July 29, 2025
• Gouvernement du Québec, Intoxication au monoxyde de carbone, up to date as of November 23, 2023
• Gouvernement du Québec, Prévenir les intoxications au monoxyde de carbone, up to date as of November 23, 2023
• Gouvernement du Québec, Prévenir les risques d'incendie dans un garage résidentiel, up to date as of September 17, 2026
• Régie du bâtiment du Québec, Qualité de l'air et intoxication, undated page, consulted on October 11, 2026
• Health Canada, Monoxyde de carbone : Prévention de l'exposition, consulted on October 11, 2026