Carbon monoxide is an invisible, odorless gas produced when you don’t completely burn off fuels like wood, oil, natural gas, propane, coal, or kerosene. It causes harmful side effects if inhaled and can even cause death.

Owning a carbon monoxide detector is just as important as having a smoke detector, and it may save your life one day.

We’ll tell you all about carbon monoxide and even help you figure out where to put your CO detector in this guide.


Where should you place a carbon monoxide detector?


Carbon monoxide is lighter than air. It also rises with warm air, so the United States Environmental Protection Agency (EPA) recommends placing a carbon monoxide detector on a wall about five feet above the floor or about eye level. You can put them on the ceiling, too.

So, where is the ideal carbon monoxide detector placement?

  • Outside of each bedroom or sleeping area.

  • Inside an attached garage.

  • On every floor, including the basement.

  • At least 10 feet from the garage door leading to your home. You should also place a sensor in the room above the garage.

  • At least 15 feet away from gas-burning appliances, like fireplaces or stoves. (These items already put off trace amounts of CO and could cause a false alarm.)

  • If you are only getting one carbon monoxide alarm, make sure it’s near a sleeping area and loud enough to wake everyone in the house.

When installing a carbon monoxide detector, make sure you:

  • Keep the alarm out of reach of children or pets.

  • Regularly check battery-operated detectors.

  • Avoid placing next to or over a fireplace or stove.

  • Install them away from the kitchen, bathroom, sunny spots, or open windows since humidity could interfere with the sensors.

  • If you require a CO alarm for a new residence, the detector should be interconnected so that when one goes off, they all go off. (Check your state requirements.)


What should you do if your carbon monoxide detector sounds an alarm?

If your CO detector sounds, you should immediately open windows and doors to allow fresh air inside and turn off any fuel-burning appliances. Then, grab your family and pets and leave the dwelling. Once you’re outside and safe, call the fire department.

If anyone in your family is sick or experiencing CO poisoning symptoms, take them to an emergency room or call 9-1-1. Doctors may need to treat them with oxygen.



What gives off carbon monoxide?


Burning charcoal, running a car, and even cigarette smoke produce carbon monoxide. However, if your appliances are maintained and used correctly, they should typically only have trace amounts of carbon monoxide gas.

It’s essential to know some common sources of CO, so you can keep an eye on those items in your home and ensure their proper maintenance and upgrading.

Common sources of CO include:

  • Boilers

  • Camping stoves

  • Water heaters

  • Furnaces or chimneys

  • Clothes dryers

  • Central heating systems

  • Generators or other gas-powered items like grills or lawn equipment

  • Fireplaces

  • Gas stoves and ovens

  • Wood stoves

  • Clothes dryers

  • Stored wood pellets

  • Automobiles

  • Open fires

  • Tobacco smoke


How is carbon monoxide measured?

Carbon monoxide is measured by parts per million (ppm), from 0 to 1000 ppm. The EPA considers 9-ppm over 8 hours to be standard or 35-ppm over 1 hour.

A good rule of thumb is that the CO levels inside your home should match levels outside. To find this number, check your city and current air quality; CO readings should be specified. Carbon monoxide levels tend to be lower in rural areas compared to urban ones.

For example, in Orlando, Florida, CO levels in 2020 were less than 1-ppm over 8 hours, well below the 9-ppm standard.


Carbon monoxide levels and their symptoms:

Symptoms are directly related to both the CO level and length of exposure. You should also consider a person’s health. Someone with lung problems or chronic heart problems may experience symptoms more rapidly.

Additionally, the build-up of carbon monoxide gas over a specific time is what sets off the alarm. For example, carbon monoxide levels would have to be at 100-ppm for 10-20 minutes or 400-ppm for a few minutes for the alarm to detect carbon gas.

Most healthy adults don’t show symptoms under 50-ppm.

  • 70-ppm: The first detectable level for UL 2034 carbon monoxide alarms after 1-4 hours.

  • 200-ppm: Healthy adults start showing signs of carbon monoxide gas poisoning. UL-approved alarms will sound off within 30-60 minutes.

    • Low-level headache

    • Nausea

    • Shortness of breath

400-ppm: Physical gas leak symptoms worsen in healthy adults within 1-2 hours, especially headaches. After three hours of exposure at this level, CO poisoning becomes life-threatening. Alarms will sound within 15 minutes.

  • Increased headache pain

  • Increased nausea

  • Dizziness

800-ppm: Healthy adults start showing increased signs of nausea, dizziness, and convulsions—within 45 minutes--then lack conscience, and brain damage or death could occur.

Since many healthy adults may not experience initial symptoms at 50-ppm, it’s essential to take any carbon monoxide sensor alert seriously to treat gas leak symptoms immediately.


Tips to protect your home from dangerous levels of carbon monoxide:


Since so many household appliances produce carbon monoxide gas, you should keep these items in clean working order.

Here are a few tips on how to properly preserve these home appliances:


  1. Maintain chimneys and flues for blockages, disconnections, or leaks. A block can prevent CO from properly escaping, which could create deadly CO levels.

  2. Avoid excessively smoking indoors, as this could cause a build-up of CO inside your home.

  3. Keep your vehicle’s exhaust pipe clear of snow.

  4. Look out for soot build-up, strange yellow or brown stains, damaged or discolored chimney bricks, rusting along flue pipes or appliance jacks, or unusual drafts surrounding gas-powered appliances.

  5. Orange or yellow flames may indicate excessive carbon levels, so you should make sure cooking or combustion flames are blue.

  6. Have your heating system, water heater, and any other gas, oil, or coal-burning appliances serviced by a qualified technician every year.


  1. Run your vehicle in an enclosed garage. CO levels may build up to dangerous levels.

  2. Handle a generator or gas-powered grill in unventilated or enclosed spaces.

  3. Use a gas range, oven, or generator inside to heat your home.

  4. Utilize a pressure washer, or other gas-operated appliance in an enclosed structure, unless the gear is installed and vented by a professional.

  5. Operate a charcoal grill, lantern, or portable camping stove inside an enclosed place, including a tent or camper.


Help protect your home from dangerous levels of carbon monoxide with ADT.


Carbon detector placement is just one crucial step in helping keep your home safe from CO poisoning. Knowing what produces CO in your home means that you can continue to maintain those appliances and be diligent about gas levels in your home.

At ADT, we’re here to help. Our 24/7 professional monitoring services alert you and the police when dangerous CO levels are detected in your home—even when you’re asleep or out of town.


Frequently Asking Questions about Carbon Monoxide Detectors

Can you smell carbon monoxide?

No. Carbon monoxide is an odorless, tasteless, and colorless gas, so you don’t typically smell it. 


What carbon monoxide levels will sound an alarm?

UL-certified carbon monoxide detectors should alert you to prolonged levels of 50-ppm.


Does a product that uses propane contain carbon monoxide?

Yes. Items that use propane, gas or natural gas, oil, coal, and wood all produce levels of CO.

How to test a CO detector?

To test the batteries in your sensor, simply press the test button. You should do this about once a month.


Typical carbon monoxide alarm life?

Batteries in a carbon monoxide detector can last for about 5-7 years.


What are the common gas leak symptoms of carbon monoxide poisoning?

Common side effects include headaches, dizziness, weakness, upset stomach, vomiting, chest pain, confusion, and death.


Should you place CO detectors on the ceilings or walls?

Like a smoke detector, you can place a carbon monoxide sensor on either the walls or the ceiling.


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