How Many Carbon Monoxide Detectors Do I Need?

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If you are here, you already realize the silent and deadly danger that carbon monoxide presents, and you need to know how best to protect your home and family. Carbon monoxide fumes can be present anytime, but wintertime is when they strike the most. 

According to the Centers for Disease Control and Prevention (CDC), over 20,000 people visit the emergency room because of carbon monoxide poisoning, and 400 unsuspecting people dieeach year. These deaths are preventable. So preventable, in fact, many states are now adopting legislation that mandates the use of carbon monoxide detectors. 

Home Installation for smoke and carbon monoxide detector

Types of Carbon Monoxide Detectors

It’s important to purchase carbon monoxide detectors that fit your lifestyle and expectations. Some require more maintenance, while others allow you to set-it-and-forget-it. 

Battery-powered carbon monoxide detectors 

These detectors are efficient in that you can install them anywhere within minutes. No wiring is required. There are two types of battery-powered detectors: a 10-year, sealed, lithium battery alarm and nine-volt or “AA” battery alarms. The major difference between the two types is the length of battery life. Carbon monoxide alarms don’t last forever, and it’s recommended you replace them every 10 years. So, while a nine-volt or “AA” battery will last you about six months before the batteries need to be replaced, the 10-year lithium battery will last until it’s time to get a new detector. 

Plug-in alarms

As the name implies, plug-in alarms are powered with an AC outlet in your home. They also have a battery backup in the event of a power system failure so that you remain protected. 

Hard-wired carbon monoxide detectors 

You can typically find hard-wired CO detectors in new or newly remodeled homes. They require special wiring and are a permanent fixture, requiring little to no maintenance, just replacement when they reach their end-of-life stage. 


You can also purchase a combination alarm that combines smoke and carbon monoxide detectors in conventional or Internet-ready models. These use ionization and/or photoelectric technologies to monitor for smoke and carbon monoxide. Some are Wi-Fi ready while others need additional equipment to connect these combination devices to the Internet. 


Interconnected devices work within your home security system by cables or via Wi-Fi. They are wired within the framework of other alarm systems, such as a theft prevention system and fire sensors. When one detector alarm sounds, it automatically triggers all interconnected devices to sound as well. We recommend these devices to those interested in a smart home or home security system, since they’re typically available in their package or as an add-on.  

Where Do I Need a Carbon Monoxide Detector?

Most individual states in the United States have adopted laws governing the use of carbon monoxide detectors. You can check the statutes of your state to make sure that you comply with the new regulations. Homes are not the only places that these detectors are required. Any structure that has a fossil-fuel burning furnace, motor, or enclosed garages is subject. Some good places to start are: 

  • Homes 
  • Garages 
  • Boats 
  • Shops  
  • Schools and daycare providers 
  • Hotels and motels 
  • Residential care facilities 

This is not a complete list, but it gives you a good starting point. Think about how many places you may have these silent, deadly fumes. 

How Many Carbon Monoxide Detectors Do I Need in My Space?

Carbon monoxide sensors are not the same as smoke detectors. They are both built to sense distinctly different hazards. Smoke is lighter than air, so it rises, but carbon monoxide is different. It is lighter than air, but its molecules are denser, giving it the ability to mix with air at lower levels. While there are different opinions about the “best” place to install your detectors, a rule of thumb is: 

  • On the wall, at least 5 feet off the ground 
  • One on every level of your home including basements and attic spaces 
  • One within 10 feet of every sleeping area or inside every bedroom 
  • Above every door that connects from your home to an attached garage 

Where NOT to Use a Carbon Monoxide Detector

There are instances where it’s not the best practice to install a carbon monoxide alarm. These places could potentially send off false-positive signals such as: 

  • Within 15 feet of a fossil fuel-burning appliance 
  • In humid areas like a bathroom 
  • In direct sunlight 
  • In a drafty space or near blowing air like near windows, vents, or fans 
  • In areas of temperature extremes of below 40 degrees or above 100 degrees. Extreme temperatures may cause the unit to fail 
  • Inside closets containing water heaters or furnaces 
  • Dead air spaces like behind furniture or curtains and drapes, wall and ceiling corners. Keep units 6” or more away from these areas. 

These should answer your question about “how many carbon monoxide detectors do I need?” If you’d like to learn more about home security systems that include carbon monoxide monitoring, please visit our top picks page

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Deborah White

Freelance Editor for SmarterHome

Deborah is an American freelance writer living in Chelem, Yucatan, Mexico, who specializes in business, marketing, and career writing. 

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