What is carbon monoxide and how do I detect it?

This surprisingly common gas is invisible, odorless and toxic. Here's what else you need to know.

Ashlee Valentine CNET Contributor
Ashlee is an MBA business professional by day and a dynamic freelance writer by night. Covering industries like banking, finance, and health & wellness, her work has been published on sites like bankrate.com, thesimpledollar.com, interest.com, womens-health.com and more. Ashlee specializes in personal finance and is passionate about helping others achieve greater financial freedom.
Ashlee Valentine
5 min read
Tyler Lizenby/CNET

You've most likely heard of carbon monoxide, but do you know what it is? Is it dangerous? Do you need a carbon monoxide detector in your home? 

Carbon monoxide, or CO, is a colorless and odorless gas commonly found in home appliances and vehicles. If you burn fuel in vehicles, small engines like lawnmowers, water heaters, clothes dryers, grills, gas fireplaces, gas ranges or gas furnaces, you have come in contact with carbon monoxide. 

Sounds pretty harmless, right? Not always. Carbon monoxide indoors or without proper ventilation can result in carbon monoxide poisoning and can be deadly. Each year in the US, more than 400 people die from unintentional CO poisoning, more than 20,000 end up in the emergency room and more than 4,000 are hospitalized. The fact that CO is odorless and invisible makes it even more dangerous, because people often do not suspect exposure until they have already become ill. If they are not familiar with the risks and CO poisoning symptoms, they may mistake those symptoms for other illnesses. This is why CO is often referred to as "the silent killer."

Keep reading to find out if your family may be at risk for carbon monoxide poisoning and the steps you can take to eliminate that risk.   

Read more: How often should I replace my fire extinguisher?

Do I have a carbon monoxide leak?

A proactive approach is always better than a reactive approach when it comes to a potentially deadly hazard. 

If you have fuel-burning appliances or an attached garage, the proactive approach is to install one (depending on the home) carbon monoxide detector near every sleeping area and on each floor of your home. These detectors are calibrated to industry safety standards determined by Underwriters Laboratories and are made to detect the unusual build-up of CO over time. If CO levels exceed industry safety standards, the detector will sound to alert you. This is the best way to determine if you have a CO leak. We'll talk more about how to buy a carbon monoxide detector later. 

Whether you have a CO detector or not, it's critical to know what signs and symptoms of CO exposure to watch out for. It is also important to understand that some people do not experience any symptoms.


Even if you have a carbon monoxide detector, it's good to keep in mind the various symptoms associated with CO poisoning.

Chris Monroe/CNET

Common symptoms of carbon monoxide poisoning

The severity of CO poisoning and speed at which it occurs depend on the concentration of CO in the home. For example, at 50 parts per million (ppm), you may be exposed for eight hours with no symptoms. Continued exposure at this level would eventually result in more hazardous build-up. On the other hand, at 12,800 ppm, within 1 to 3 minutes of exposure, a person may be rendered unconscious and die. 

If you think you or someone in your home has been exposed to CO, call the national toll-free Poison Help hotline at 1-800-222-1222. If the condition is severe, you should call 911.

These are the most common symptoms associated with CO poisoning.

  • Headache
  • Upset stomach
  • Vomiting
  • Dizziness
  • Weakness
  • Chest pain
  • Confusion
  • Unconsciousness
  • Shortness of breath
  • Relief from symptoms when away from home
  • More than one person in the home is affected with similar symptoms.
  • Pets seem ill
  • You experience the above symptoms, but lack other symptoms that are generally associated with colds and flu, like fever, body aches and enlarged lymph nodes. 

How to find carbon monoxide leaks

The most common cause of CO leaks is poorly maintained or poorly ventilated gas-fueled household appliances. But other things, like blocked flues and chimneys and faulty or restricted car exhausts, can lead to a build-up of CO, too. Here are some ways to identify potential carbon monoxide leaks:

  • Brownish or yellowish stains around appliances
  • A pilot light that frequently goes out
  • Burner flame appears yellow instead of clear blue (exception: natural gas fireplaces)
  • No upward draft in chimney flue
  • Stale-smelling air
  • Soot, smoke or back-draft inside the home

If you find any of these issues, take action fast. The best way to prevent CO leaks is to have your home's fuel-powered equipment thoroughly inspected each year.

Protecting the CNET Smart Home from floods, fires and more

See all photos

How to prevent carbon monoxide poisoning

Prevention is the best approach with carbon monoxide poisoning. Even if CO poisoning isn't deadly, it can cause long-term or permanent damage to vital organs like the brain, heart and lungs. CO is known to be so damaging that there is a long-standing debate on whether people who have been poisoned by carbon monoxide can be organ donors. Suffice it to say, carbon monoxide poisoning is a serious issue with potentially long-lasting effects. So, how can you keep it from happening?

Carbon monoxide detectors

The National Fire Protection Agency recommends installing a carbon monoxide detector outside each sleeping area and on each floor of your home. You should also check with local laws and building codes to ensure CO alarms are installed anywhere they are required. 

Be sure to install CO detectors that have a recognized testing laboratory, like Underwriters' Laboratories. If your home is a smart home, options like the Nest Protect, First Alert and Roost include smoke and carbon monoxide detection. Regardless of which alarm you decide to install, do so according to the manufacturer's instructions, as these are tested for optimal accuracy and protection. 

Test your CO detectors on the same schedule you test your smoke detectors -- once per month. 


If you have gas-fueled appliances, it's important to have them properly installed and regularly inspected.

Tyler Lizenby/CNET

Equipment maintenance

We mentioned this when discussing finding and preventing CO leaks, but it's worth mentioning again. Have all your fuel-powered appliances inspected yearly. If you buy new appliances, be sure they are installed by a qualified professional. Have your chimneys and flues inspected annually as well. 

Not every CO issue originates inside the living area of a home. Attached garages are common culprits. Make sure to remove fuel-burning equipment from the garage before starting them and repair or replace any that are not working properly. Never leave your car running inside the garage without the door open, and have the exhaust system inspected for leaks regularly. 

If you live in an area prone to power outages and have a portable generator, be sure to use the generator outdoors only. 

No indoor smoking

Heavy smoking can cause carbon monoxide poisoning. In smokers, the concentration of carboxyhemoglobin (CO bound to hemoglobin) is usually between 3% to 8% and up to 15%, whereas in non-smokers, it is usually 1%. If you're smoking in an enclosed area, others may also be affected by the CO. 

The conclusion on carbon monoxide

Encountering carbon monoxide is inevitable if you use fuel-powered appliances or equipment in your home or garage. The goal is not to eliminate CO but to prevent its ability to build up in our living spaces and vehicles and take the proper precautions to alert you if build-up occurs. A carbon monoxide detector is the best way to ensure you'll be alerted to carbon monoxide exposure before it becomes a more serious health hazard to you and your family.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.