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Are Smoke and Carbon Monoxide Detectors Different? 

  • Safety Tips
  • Celine Jerly
  • 5 minutes

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Most homes have a smoke alarm, but does it detect carbon monoxide? Smoke and Carbon Monoxide detectors are not so different – at least in their basic function. So, can the same device warn you about high smoke and CO gas levels? How and where should you install these devices for maximum safety? Find out more right here: 

Smoke and Carbon Monoxide detectors usually look the same – these are small battery-operated devices installed on ceilings or walls. As smoke alarms are much more common, most people do not realize it when they see a carbon monoxide (CO) detector. However, they are different, and here’s how to tell them apart. 

Also See: Know More about Carbon Monoxide Poisoning from a Gas Stove

Is a carbon monoxide detector the same as a smoke detector? 

Smoke and carbon monoxide detectors are separate devices unless the sensor has dual functions.  

Smoke detectors are primarily used for fire safety in homes and other buildings. When smoke or other harmful fumes from fires rise to dangerous levels, the sensor in these devices sets off an alarm. A heat detector is sometimes used as an additional safety device but is not as effective as a smoke alarm.  


A carbon monoxide detector has a specific function – to detect the odorless, tasteless, colorless, and flammable CO gas. Carbon monoxide is dangerous to your health and even fatal in high quantities. Faults with the combustion process, such as in car engines or heaters, are the main cause of CO leaks.  

Nowadays, dual function – smoke and carbon monoxide detectors – are available. So, yes, some smoke detectors can detect carbon monoxide.  

How do smoke and carbon monoxide detectors work? 

Smoke alarms and carbon monoxide detectors usually work on batteries; even wired devices will have batteries as a backup power source. They could also be a series of alarms connected throughout the building or operate individually. Both detectors are available at different price points – from entry-level to high-end. In any case, smoke and carbon monoxide detectors work in similar ways: 

When the CO gas or smoke reaches the detection field, it causes a chemical reaction that produces an electric current that sets off the audible alarm. In the case of dual-function detectors, both alarms may not go off – there can be smoke without carbon monoxide and vice versa.  


Smoke alarms usually beep three times in a row, while carbon monoxide alarms are four simultaneous beeps. A single beep is generally a low battery warning, or it’s time to replace your smoke alarm. Overall, smoke and carbon monoxide detectors are low maintenance – you just need to ensure the battery isn’t dead.  

With new tech, we also have smoke detectors that alert you via voice and give safety directions. For the hearing impaired, smoke and CO alarms that shake your pillow or have strobe lights are available. 

Where should I position a CO detector? 

Smoke detectors are placed on the ceiling as smoke rises. But carbon monoxide won’t rise as quickly as smoke – so you must place them on the walls. If you have a gas furnace or heater, place a CO detector near them or outside the room. The same goes for any gas-powered appliance or equipment.  

You can install dual-function detectors on the ceiling. Most people start noticing symptoms of CO exposure at about 50 ppm; set your detector to sense and alert if the gas is at this level or less.  

what causes carbon monoxide exposure infographic

When should you replace CO detectors? 

Carbon monoxide detector replacements depend on the model, but 5-7 years is the safe option. Or, check the replacement frequency suggested in the device’s manual. 

You need to replace smoke alarms every 7-10 years as long as it’s working fine. After ten years, the detector burns through batteries faster, and the sensors begin to deteriorate, leading to false readings. 

Replace batteries in smoke and carbon monoxide detectors at least once a year. Remember, wire-mounted smoke alarms also have batteries for backup power. Frequent beeps from the detector, without relevant cause, might be an indication of weak batteries.  


How do I know if my smoke alarm detects carbon monoxide? 

Not sure if you are looking at a device that detects smoke, carbon monoxide , or both?  

The first step to solving the confusion is to inspect the device itself. Remove it from the mount to check the backside – twist it counterclockwise. To remove wall-mounted CO detectors, unplug them from the socket.  

If the alarm device detects CO gas, you’ll find the text “Carbon Monoxide Alarm” and a safety check emblem that reads “CSA,” “IAS,” or “UL.” Devices without markings or descriptions are either not up to safety standards or do not detect carbon monoxide.  

To be sure, run an online search with the smoke detector’s model number and manufacturer/brand name. The model number is usually a series of numbers and letters on the device. If your smoke detector has dual functions, the manual or the manufacturer’s website will mention it.  

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