Do All Homes Need a Carbon Monoxide Detector?

Most homes do, but the need is highest wherever fuel gets burned. A gas furnace, gas water heater, gas stove, gas dryer, wood fireplace or attached garage all give CO a path into the living space.

CO is colorless, tasteless and odorless, so you can't rely on your senses. An alarm is the only way to know levels are rising before symptoms such as headache or dizziness appear.

Homes without any of those sources are at lower risk, but "lower" is not "none". A portable generator used during an outage, a grill wheeled close to a door or a car idling in the garage can still produce CO.

That's why we treat a CO alarm as basic safety gear in nearly every home. Our guide to how many carbon monoxide detectors you need covers the count room by room.

Which homes have the highest carbon monoxide risk?

Homes with gas appliances plus an attached garage carry the most risk. The two sources share walls with where you sleep, so a leak or a running engine reaches bedrooms quickly.

Older furnaces and water heaters are worth watching closely. A blocked flue or a cracked heat exchanger can send exhaust indoors instead of up the chimney.

A fireplace or wood stove adds risk when the flue doesn't draw well. So does any home with a generator, a gas range used for long cooking sessions or a garage workshop with fuel-powered tools.

Renters face the same risks as owners. If your landlord hasn't installed an alarm, a plug-in unit you can take with you is the simplest fix.

Can an all-electric home skip a carbon monoxide detector?

An all-electric home can go without one, though many owners still add a single alarm as cheap backup. With no gas line, no fireplace and no attached garage, there are almost no CO sources inside the home.

The usual exceptions are worth checking. A generator run in the yard, a gas grill near a window or a car parked close to an open door can all push CO indoors.

If you charge a car in an attached garage or keep a fuel-powered mower there, treat the home as if it had a gas appliance. Add an alarm near the door between the garage and the house.

Homes that use a gas space heater or a gas log set are not truly all-electric. Any open flame or fuel burner counts, even if it's only used in winter.

Where should a carbon monoxide detector go?

Put one near each sleeping area and one on every level of the home. That covers the places where CO can harm people while they sleep and where it can build up unnoticed.

Add a unit in the same room as a fuel-burning appliance when the maker allows it. A detector in the furnace room catches a flue problem early.

Keep units at least 15 feet from gas stoves and 10 feet from furnaces, per common manufacturer guidance. Heat and humidity near those appliances can cause false alarms.

Mount alarms at eye level or higher on a wall, or on the ceiling, following the unit's instructions. Avoid dead-air spots behind furniture and corners where air doesn't circulate.

What about a detector in the garage?

Place one in the room next to the garage, not inside it. Garage temperatures swing widely and exhaust fumes from a cold start can trip an alarm that's mounted too close to the door.

Should you pick a plug-in or battery carbon monoxide detector?

A plug-in alarm with battery backup is the most reliable choice for most homes, because it runs on wall power and keeps working when the power fails. A sealed 10-year battery unit is the better fit when there's no outlet near the ideal spot.

Here are three units that match common situations. Our guide to how to choose a carbon monoxide detector covers sensor types and features in more depth.

Best for outlet-friendly spots

The Kidde Plug-In CO Alarm with Digital Display runs from a standard 120V outlet and keeps a 9V battery as backup. Its digital display shows the CO level the alarm is sensing and updates as conditions change.

Peak Level Memory records the last time CO was detected or the unit was tested. The 85 dB alarm and Smart-Hush button make it easy to manage, and an extension cord is included for table or shelf placement.

Best for homes without nearby outlets

The First Alert CO710 runs on a built-in 10-year lithium battery, so placement isn't tied to an outlet. It's a tabletop unit with a backlit display that shows temperature and CO concentration.

The electrochemical sensor is the type First Alert calls the most accurate CO detection technology. An end-of-life chirp tells you when to replace the whole unit.

Best for covering smoke and CO together

The Kidde 30CUD10 combines smoke and carbon monoxide detection in one unit with a built-in 10-year battery. It uses photoelectric and electrochemical sensors and a red LED for visual notification.

Kidde says the sensing technology detects smoke over 25% faster on average in internal smoldering-wood tests. It's tested to UL 217 10th Edition and UL 2034 5th Edition.

How do you keep a carbon monoxide detector working?

Test each alarm monthly and replace it by its end-of-life date. Press the test button and confirm the alarm sounds, then clear any dust from the vents.

Follow the steps in our guide to how to test a carbon monoxide detector so you test the right way. A test confirms the alarm and battery, not the sensor's accuracy.

Replace backup batteries once a year in units that use them. Sealed 10-year units don't need battery changes, but the whole alarm still gets replaced when the end-of-life signal sounds.

Keep the unit clear of dust and lint, and don't paint over the vents. Avoid mounting near bathrooms, where steam can cause false alarms.

What should you do if the alarm sounds?

Get everyone outside to fresh air and call 911 from outside the home. Don't re-enter to open windows or find the source, even if the alarm stops on its own.

Once outside, account for everyone in the household, including pets. Tell the fire department if anyone has symptoms such as headache, dizziness, nausea or confusion.

Don't reset the alarm and go back inside. Firefighters will check CO levels and help find the cause before it's safe to return.

If the alarm sounds and no one feels ill, it may still be a real reading. Treat every alarm as real until a responder says otherwise.

What if your home has no fuel-burning appliances?

A detector is optional in a truly all-electric home without a garage, but the cost is small next to the risk from generators, grills or a car left running nearby. Many owners keep one near the bedrooms anyway.

Check whether your home has a gas line, a gas log, a propane heater or a garage before deciding. Any one of those tips the answer toward yes.

A plug-in unit suits a rental or a home where you want to move the alarm as needs change. Compare models in our roundup of the best plug-in carbon monoxide detectors.

Bottom line

So do all homes need a carbon monoxide detector? Any home that burns fuel, has a fireplace or shares a wall with a garage should have one, and most others benefit from at least a single alarm near the bedrooms.

Pick the Kidde plug-in for an outlet-friendly spot, the First Alert CO710 for a tabletop placement without wiring, or the Kidde 30CUD10 when you want smoke and CO coverage in one unit.

Then test monthly and replace on schedule.

Frequently asked questions

Where should a carbon monoxide detector be placed?

Put one near each sleeping area and on every level of the home. Add one in the same room as a fuel-burning appliance or fireplace and near an attached garage, and keep units at least 15 feet from gas stoves and 10 feet from furnaces.

Is a plug-in or battery carbon monoxide detector better?

A plug-in alarm with battery backup gives you both wall power and backup during an outage. A sealed 10-year battery alarm works without wiring, so it suits homes without an outlet near the best spot.

How long does a carbon monoxide detector last?

Most CO alarms last about 7 to 10 years, and many chirp when they reach end of life. Check the replace-by date on the unit and swap it on schedule, because the sensor weakens with age even if the alarm still sounds.

Do All Homes Need a Carbon Monoxide Detector?