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Where Should Carbon Monoxide Detectors Go?

by the Berry team · Updated

If your home has any fuel-burning appliance, like a gas furnace, water heater, range, dryer, or fireplace, or has an attached garage, put a carbon monoxide alarm outside each sleeping area and on every level of the home. Follow the manufacturer instructions for height and spacing, and keep alarms out of kitchens, bathrooms, and spots right next to fuel-burning appliances, where they can give false alarms.

Types of CO alarms and what they cost

Ranges are typical US prices per alarm.

Plug-in CO alarm with battery backupEasy placement near bedrooms where an outlet is at a reasonable spot.DIY$20-$50ProNot needed
Battery CO alarmAnywhere, including rooms without a convenient outlet. Sealed 10-year battery models need no battery changes.DIY$20-$50ProNot needed
Combination smoke and CO alarmCovers both in one device, fewer things on the ceiling. Uses voice alerts on many models to tell you which hazard.DIY$30-$60Pro$100-$250 hardwired, installed
Hardwired, interconnected CO alarmsAll alarms sound when one detects CO. Common in newer homes.DIYNot recommended unless replacing like for likePro$100-$300 per alarm installed

Ranges are typical US prices and vary with your region, your home, and the season. A pro quote for your exact job beats any range.

Does your home need CO alarms?

Carbon monoxide comes from burning fuel. If your home has any of these, you need CO alarms:

  • A gas, oil, or propane furnace or boiler.
  • A gas water heater.
  • A gas range, oven, or dryer.
  • A fireplace, wood stove, or gas logs.
  • An attached garage, where a running car or generator can push CO into the house.

Many states and cities require CO alarms in homes with fuel-burning appliances or attached garages, especially when a home is sold or renovated. Even if yours is all electric, a CO alarm is inexpensive protection against a generator or car running too close to the house.

Where to put them

  • Outside each sleeping area. In the hallway near bedrooms, close enough to wake people.

  • On every level. Including the basement, especially if the furnace or water heater is there.

  • Inside bedrooms, if a fuel-burning appliance is in or near one. For example, a bedroom next to the furnace room or above the garage.

  • At the height the manufacturer says. Carbon monoxide mixes with air, so placement guidance varies by model. Follow the instructions in the box.

Where not to put them

  • Right next to a furnace, water heater, range, or fireplace. Small amounts of CO at startup can cause false alarms. Many manufacturers recommend keeping alarms several feet or more away.
  • In kitchens and bathrooms, where steam, humidity, and cooking can cause false alarms or shorten the sensor life.
  • Near windows, doors, fans, or vents, where fresh air can dilute CO before the alarm detects it.
  • In garages, unless the alarm is rated for that location. Temperature swings and exhaust are hard on sensors.

If the CO alarm goes off

  1. Get everyone outside into fresh air right away, including pets.
  2. Call 911 or the fire department from outside. Do not go back in until they say it is safe.
  3. Watch for symptoms like headache, dizziness, nausea, confusion, or sleepiness. Get medical help if anyone has them.
  4. Have a technician check fuel-burning appliances and venting before using them again.

Testing and replacing

Test CO alarms monthly with the test button. CO sensors wear out, and many alarms are designed to last somewhere around 5 to 10 years. Check the replace-by or manufacture date on the back, and replace the alarm when it reaches it. Many will chirp in a distinct pattern at the end of their life. See why a detector chirps. Fuel-burning appliances themselves should be serviced regularly, see furnace short cycling for warning signs on a furnace.

When to call a pro

  • A CO alarm goes off. Get everyone out and call 911 or the fire department from outside.
  • You notice soot, a yellow or flickering flame on a gas appliance, or a stuffy, stale feeling near a furnace or water heater.
  • You want hardwired, interconnected CO alarms added or replaced.
  • You have fuel-burning appliances that have not been serviced in years.

What makes it worse if you wait

  • Carbon monoxide is invisible and odorless. Without a working alarm, early symptoms can be mistaken for the flu.
  • Blocked flues and cracked heat exchangers can get worse, increasing CO levels over time.
  • CO alarms past their replace-by date may not detect CO reliably.

Common questions

Where should carbon monoxide detectors be placed?

Outside each sleeping area and on every level of the home, including the basement. Follow the manufacturer instructions for height. Keep them out of kitchens and bathrooms and away from fuel-burning appliances, windows, and vents.

How many carbon monoxide detectors do I need?

At least one on every level and one outside each separate sleeping area. Larger homes or homes with bedrooms near a furnace room or attached garage may need more.

Do I need a CO detector if I have no gas appliances?

If you have no fuel-burning appliances and no attached garage, the risk is much lower. Many people still keep one, since generators, cars, and grills used too close to the house can bring CO inside.

How long do carbon monoxide detectors last?

Many are designed to last around 5 to 10 years. Check the replace-by or manufacture date on the back, test monthly, and replace the alarm when it reaches its date or chirps an end-of-life warning.

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