Carbon Monoxide Detector: How it Works & Where to Place Them

As an odourless, tasteless, and colourless gas, carbon monoxide (CO) has earned the ominous moniker as the “silent killer.”

Any household with a gas appliance—whether for cooking or heating—is especially susceptible to carbon monoxide poisoning. And without the proper equipment in place, it could kill you quietly while you sleep. Around 70% of Australian households use gas as an energy source; there’s a good chance you do, too.

If you’ve yet to get a carbon monoxide alarm installed, we recommend checking out this guide—it could save your life one day. Read on to learn what carbon monoxide is, how a carbon monoxide detector works, and where to install one in your home.

Table of Contents

What is Carbon Monoxide?

Carbon monoxide is a gas that appears when burning common fuels such as propane, petrol, charcoal, and wood. Although natural gas is the most common cause of carbon monoxide poisoning, other sources like heaters, driers, ovens, oil-fired boilers, fires, and car engines can also emit the deadly gas.

Normally, carbon monoxide gets safely diverted to the open air through a chimney or flue. However, if an exhaust system fails—whether due to blockages, incorrect installation, or poor maintenance—noxious gas will begin building up in the room.

When carbon monoxide is inhaled, even in small amounts, it causes carbon monoxide poisoning, potentially resulting in severe injury or death. On average, one Australian dies of carbon monoxide poisoning each year, and around 20 others are injured. The elderly, infants, and people with respiratory illness are particularly vulnerable, although the gas can prove fatal to anyone.

Carbon monoxide is slightly lighter than air, so it will begin filling a room from the top down. Although poisoning causes symptoms such as dizziness and headache, these aren’t always immediately obvious. Many people have died in their sleep without ever realising something was wrong.

What is a Carbon Monoxide Detector?

A carbon monoxide detector (AKA, carbon monoxide alarm) is, as the name implies, a device that detects carbon monoxide and sounds an alarm. It’s important not to confuse it with a smoke alarm, as the two detect entirely different things. The safest option is to install both devices in your home.

Carbon monoxide detectors come in three distinct types:

Biometric sensors have a unique gel inside the alarm that changes colour when it detects carbon monoxide. A sensor detects the change and sounds an alarm.
Metal oxide semiconductor sensors detect a change in electrical resistance when carbon monoxide is present, which triggers an alarm.
Electrochemical sensors have a chemical solution that alters the current in the presence of carbon monoxide, which triggers an alarm.

Carbon monoxide detectors are also powered in two distinct ways:

Battery-powered alarms use standard alkaline batteries, which must be replaced every year or so. No professional installation is required, and the alarm will automatically notify the homeowner when the battery starts running low.
240V alarms must be hardwired into the mains power of the home by a licensed electrician. These devices typically include a rechargeable backup lithium battery, which won’t need changing over its lifespan.

The best devices can be linked to an existing smoke detector so that all alarms sound simultaneously in an emergency (either smoke or carbon monoxide).

It’s possible to purchase a carbon monoxide detector wholesale or for individual use.

Where to Place a Carbon Monoxide Detector?

If you’ve got a 240V alarm, you’ll need to get a licensed electrician to install it. You can safely position a battery-powered alarm yourself, but be sure to consider the following.

Because carbon monoxide is lighter than air, position your alarm at least two meters from the ground (15cm below the ceiling is ideal).
Ideally, install an alarm in every room with a fuel-burning appliance. Failing that, put one in a central area like a hallway.
Don’t put the detector within one meter of a fuel-sourcing appliance, including fireplaces, to avoid nuisance alarms.
Position at least one alarm close enough to your bedroom to wake you up in an emergency.
Avoid positioning the alarm in enclosed spaces like cupboards or behind furniture.
Don’t put an alarm near windows, exterior doors, or exhaust fans—anywhere the gas could naturally vent outside.
Avoid positioning the alarm in moist or high condensation areas like bathrooms.

By following these tips, you can be sure your carbon monoxide alarm will function correctly in an emergency. In any case, always read the manufacturer’s instructions and test your alarm as per their recommendations.