Carbon monoxide (CO) is often called the ‘silent killer’ because it is an invisible, odourless gas that can be deadly.
CO poisoning causes dozens of accidental deaths each year and many more illnesses.
The best protection against this danger is a carbon monoxide detector.
A carbon monoxide detector is a small alarm device that can alert you to CO gas in the air before it harms you.
However, installing the detector in the right place is crucial.
What is a Carbon Monoxide Detector?
A carbon monoxide detector (also known as a CO alarm) is a safety device designed to detect the presence of carbon monoxide gas.
It serves a similar role to smoke detectors, but instead of sensing smoke, it monitors for carbon monoxide.
Because carbon monoxide is impossible for us to detect on our own, a detector is often the only way to know if this gas is building up in your home.
Carbon monoxide detectors are typically small, battery-powered or mains-powered units that can be mounted on a wall or ceiling.
They continuously sample the air for CO.
If the device senses a dangerous concentration of carbon monoxide, it will emit a loud, high-pitched alarm to warn everyone in the vicinity.
Many modern CO alarms also have test buttons and indicator lights, and some models include digital displays to show CO levels.
Basically, a carbon monoxide detector acts as an early warning system .
It will alert you as soon as CO is present at hazardous levels, giving you time to ventilate the area or evacuate.
By installing CO detectors in your home, you can be warned of a carbon monoxide leak before it reaches life-threatening levels.
Where to Install a Carbon Monoxide Detector in Your Home
Knowing where to install your carbon monoxide detectors is just as important as having them.
To provide effective protection, detectors should be placed in locations where they can detect CO quickly and alert people throughout the home.
The general rule is to install CO alarms near any potential source of carbon monoxide, and near areas where people sleep.
This ensures that if a dangerous CO leak occurs, the alarm will pick it up early and wake you up if you’re sleeping.
Here are some guidelines for positioning CO detectors in your home:
In Rooms With Fuel-burning Appliances
Place a detector in each room that contains a potential CO source, such as a gas boiler, gas fire, wood-burning stove, or gas cooker.
For example, if you have a gas boiler in the kitchen or a fireplace in the living room, install a CO alarm in those rooms.
It should be installed at a distance of 1–3 metres from the appliance, if possible, rather than right next to it.
This distance helps the detector sample the air in the room effectively without being immediately exposed to small transient puffs of exhaust from the appliance.
Avoid placing it directly above a cooking appliance or fire, to prevent false alarms from normal fumes or steam.
Near Bedrooms and Living Areas
It’s crucial to have a carbon monoxide detector where it can be heard if you are sleeping.
CO alarms should be located close to where you sleep.
This includes in each bedroom or in the hallway just outside sleeping areas.
If carbon monoxide leaks at night, an alarm near the bedrooms will sound and wake people up.
In living spaces like lounges or any room you spend a lot of time in, position a CO detector at roughly head height.
On Each Level of a Home
Ideally, have at least one CO detector on every floor of your house.
For a two-storey house, that means one upstairs and one downstairs.
In a single-storey property or apartment, make sure the one alarm you have is located centrally where its alarm can be heard throughout, and not too far from the main bedroom.
Height and Positioning
Carbon monoxide detectors can be installed on the ceiling or high up on a wall.
Carbon monoxide has roughly the same density as air and also tends to mix with warm air rising from appliances.
Therefore, you should place the detector at a height where it will detect the gas in the room’s air column.
If wall-mounting, put it at least as high as any door or window in that room and about 1.5 metres from the floor.
If ceiling-mounting, it should be at least 30 cm away from the nearest wall, since corners or edges of the ceiling can create dead air space.
Always follow the manufacturer’s mounting instructions specific to your detector model, as some detectors are designed to be wall-mounted and others on the ceiling.
Garages
If your home has an attached garage, it is wise to install a CO alarm in the room adjacent to the garage door.
Car exhaust is a common source of carbon monoxide, and fumes can seep into the house from the garage.
By placing a detector near the internal door to the garage, you’ll be warned if a car left running or any petrol tools in the garage are causing CO to enter your home.
How Does a Carbon Monoxide Detector Work?
A carbon monoxide detector works continuously to sniff out any CO gas.
Most modern CO detectors use an electrochemical sensor to detect carbon monoxide.
This sensor reacts with CO gas and generates an electrical signal proportional to the concentration of CO present.
In simple terms, the detector is constantly measuring the parts-per-million (ppm) level of carbon monoxide in the surrounding air.
When the CO level climbs too high, the detector’s built-in alarm is triggered.
Carbon monoxide detectors are designed to activate before healthy adults start feeling symptoms of poisoning.
They often operate on a concentration-time function.
Even relatively low CO concentrations will set off the alarm if they persist for several hours, while higher concentrations trigger the alarm much faster.
This ensures you are warned in time to take action.
Power Supply
Most CO alarms on the market are battery-powered, though some plug into mains outlets or are hard-wired into a home’s electrical system.
Regardless of power source, they all function similarly.
Alarm
The alarm sound is distinct and piercing (often an intermittent series of loud beeps).
It is designed to be audible enough to wake people from sleep and alert everyone in the house.
Where Not to Install a Carbon Monoxide Detector
Installing your carbon monoxide detector in the wrong place can undermine its ability to protect you.
It may lead to false alarms or, worse, failing to alarm when it should.
To ensure your CO alarm works effectively, you need to avoid certain bad locations and placement mistakes.
Let’s look at where not to install a carbon monoxide detector:
Blocked or Enclosed Spaces
Never install a CO detector inside a cupboard, behind heavy furniture, or in any enclosed space.
The sensor needs access to circulating air to detect CO.
If it’s obstructed or hidden, it may not sense the carbon monoxide until it’s too late.
Similarly, don’t put it in a narrow corner or at floor level behind curtains.
Keep it out in the open where air flows freely around it.
Too Close to Appliances
While you want the detector in the same room as a fuel-burning appliance, placing it right next to or above the appliance can be problematic.
For instance, mounting a CO alarm directly above a gas cooker or very close to a boiler could lead to nuisance alarms.
If the detector is too close, it might alarm unnecessarily.
These frequent false alarms can cause people to become desensitised or to disable the alarm.
For that reason, a minimum distance (often about 1–3 metres or roughly 10 feet) is recommended between the alarm and the appliance.
This way the detector monitors the general air in the room, not just the immediate vicinity of the appliance’s exhaust.
Near Windows, Vents, or Fans
Avoid installing a carbon monoxide detector right next to a window, exterior door, air vent, or ventilation fan.
Draughts and fresh air from outdoors can dilute the carbon monoxide in that area, so the detector might not register the gas even if CO is present elsewhere in the room.
CO could be building up in a different part of the room while fresh air near the detector keeps it low at that spot.
Likewise, being next to a heating or air conditioning vent can blow air on the sensor and potentially prevent it from detecting CO.
Always place detectors at least a few feet away from any sources of strong drafts or ventilation.
High Humidity
Do not install CO alarms in bathrooms or above cookers and kettles where they will be exposed to a lot of steam and humidity.
Excess moisture in the air can interfere with the sensor and lead to false alarms or corrosion over time.
A hot steamy shower could trigger a nearby CO alarm falsely, or constant humidity might damage its electronic components.
Keep detectors out of very damp areas like bathrooms, laundry rooms, or right next to humidifiers.
The same goes for areas with grease or smoke from cooking.
Grease buildup can clog the sensor opening.
It’s best to have the kitchen CO detector at least a few metres away from the hob or oven.
Extreme Temperatures
CO detectors generally should be used in living spaces.
Placing one in an environment that is extremely cold or hot (outside the typical range of about -10°C to 40°C) can cause it to malfunction.
If you put a detector in an unheated garage or attic that freezes in winter, its battery or sensor might not work properly.
Instead of mounting an alarm inside a potentially extreme environment like a loft or garage, mount it in the adjacent room where it will still detect CO.
Always check the manual as it will specify the acceptable temperature and humidity range for the unit.
Out of Earshot
An often-overlooked ‘wrong place’ is any location where you would not hear the alarm.
Remember that the purpose of a CO detector is to wake you or alert you to danger.
If you install one in a far corner of the basement but you sleep two floors up, that’s not going to be very useful unless the alarms are interconnected.
Make sure at least one alarm is close enough to sleeping areas that it would wake everyone up.
If you have a large home, consider interconnected alarms that all sound if one detects CO, so you can hear the alert everywhere.
For a standard standalone detector, place it within hearing range of bedrooms.
Carbon Monoxide Sources in Your Home
We’ve talked about where to put CO detectors, but what are the common sources of carbon monoxide inside a home?
Carbon monoxide is produced by the incomplete burning of carbon-based fuels.
This means any appliance or equipment that burns gas, coal, wood, oil, petrol, charcoal, or other fossil fuels can potentially produce carbon monoxide.
In a household setting, several sources can create CO gas:
Gas-fired Appliances
This includes gas boilers (central heating systems), gas water heaters, gas fires in fireplaces, and gas cookers/ovens.
When working correctly, these appliances burn gas (natural gas or LPG) cleanly to produce heat.
However, if they are faulty, poorly ventilated, or not properly adjusted, they can produce carbon monoxide.
For example, a boiler with a blocked flue or a cooker with a yellow, inefficient flame can release CO into your kitchen or utility room.
It’s one reason regular servicing of gas appliances is so important.
Solid Fuel and Wood Burning Appliances
Wood stoves, coal stoves, open fireplaces, and pellet burners can all emit carbon monoxide.
Solid fuels naturally create CO as they smoulder and burn.
If you have a chimney or flue that’s partially blocked or a stove that isn’t drawing properly, CO can spill back into the room.
Even dying embers in a fireplace overnight can produce CO.
Always ensure chimneys are clear and well-maintained, and have a CO detector in any room with a fireplace or wood-burning stove.
Vehicle Exhaust
If you have an attached garage, a prime source of carbon monoxide is a car engine.
Running a car in a garage can build up CO.
If the garage is attached to the house, the gas can seep through doorways or any small gaps into the home.
This is why it’s essential to have detectors near the door to an attached garage and of course.
Never leave vehicles running inside the garage with the door closed.
Even with the garage door open, CO can accumulate in the garage and drift indoors.
Some people warm up cars in winter or leave engines running unwittingly and a CO alarm can pick up the danger if those fumes begin entering the home.
Key Takeaways
You should now have more of an understanding of where to install a carbon monoxide detector in your home.
Carbon monoxide detectors are a simple but vital addition to any home that has a fuel-burning appliance.
They provide an early warning of a deadly gas that you cannot see or smell.
By following the placement guidelines outlined above, you and your family will be alerted in time to act.
Always remember to maintain your detectors: test them regularly and replace the batteries as needed.
Additionally, maintain your fuel-burning appliances with regular servicing to prevent CO problems at the source.
In a house equipped with properly placed carbon monoxide detectors, you can rest easier knowing you have a watchdog against this silent hazard.
The shrill beeping of a CO alarm at 3 AM might be jarring, but it could save your life.
It’s far better than the alternative of not knowing about a carbon monoxide leak.
