Where to Place Carbon Monoxide Detectors: 5 Rules (2026)
Where to place carbon monoxide detectors: one on every floor, outside each sleeping area, 5 to 20 feet from fuel-burning appliances. Five rules for 2026.
Put one carbon monoxide detector on every floor, outside each sleeping area, and 5 to 20 feet from any fuel-burning appliance such as a furnace, water heater, or fireplace. That covers most houses. The five rules below handle the rest: rooms to skip, distances that matter, and keeping alarms awake through a power outage.
The timing is not subtle. In May 2026, ahead of the June 1 start of Atlantic hurricane season, the U.S. Consumer Product Safety Commission issued its annual warning about generator carbon monoxide, fire, and gas hazards after storms. Every hurricane season follows the same script: the power fails, a portable generator comes out, and someone runs it in a garage or too close to a window. CO is odorless and colorless, and it can disable a household in minutes. Detector placement is the part you can finish this weekend, before the outage.
The basics
- Every floor gets one, including the basement. A single alarm by the front door does not protect upstairs sleepers.
- Bedrooms first. Alarms go outside sleeping areas, close enough and loud enough (85 dB is standard) to wake people up.
- Give appliances space: 5 to 20 feet from furnaces, water heaters, fireplaces, and stoves. Too close means nuisance alarms or a dead sensor; too far means late warning.
- Outages are the danger window. Generators, space heaters, grills used as heaters, and cars idling for warmth all make CO. Battery-powered alarms keep working when the grid does not.
- Detectors expire. Most last 7 to 10 years. The manufacture date is printed on the back; an end-of-life chirp means replace, not re-battery.
Where to place carbon monoxide detectors: the 5 rules
Rule 1. One on every level, basement included. The EPA guidance is one detector per floor, and the basement counts because furnaces and water heaters usually live there. A ranch house needs at least one; a two-story with a basement needs at least three. Hallways connecting levels are good spots when a floor has no better option.
Rule 2. Outside each sleeping area. Place the alarm in the hallway serving the bedrooms, within hearing distance of the doors. If bedrooms sit at opposite ends of the house, each cluster gets its own alarm. For extra coverage, manufacturers and fire agencies alike accept an alarm inside the bedroom itself, especially for deep sleepers and children.
Rule 3. Set back 5 to 20 feet from fuel-burning appliances. Kidde, one of the two big alarm makers, recommends 5 to 20 feet from sources such as furnaces, water heaters, and fireplaces. Never mount an alarm directly above or beside a stove or fireplace: cooking fumes and brief puffs of exhaust cause false alarms that train people to ignore the real one. Measure the setback before you drill.
Rule 4. Keep them out of the rooms that ruin them. No alarms in the garage (engine exhaust), the kitchen (cooking fumes), humid bathrooms (steam), or right next to drafty windows and vents. Skip the dead-air corner where a wall meets a peaked ceiling, and keep alarms clear of curtains and furniture that block airflow. A detector that cannot sample room air is wall decor.
Rule 5. Keep them powered, tested, and current. Test monthly with the test button. Swap replaceable batteries yearly unless the model seals them in for 10 years. Vacuum the vents twice a year; dust and pet hair clog sensors. Write the install date on the unit with a marker and replace it at end of life. If your state or city requires interconnected alarms, link them so one alarm trips them all.
Which detector to buy
Three picks cover the three jobs. Prices are current Amazon listings checked September 2026.
Every home: battery-powered alarm on each floor. The Kidde Battery-Powered Carbon Monoxide Detector runs about $24, carries a 4.7 star owner rating, and sounds an 85 dB alert from an electrochemical sensor with event memory. Two included AA batteries keep it listening through a power failure, which is exactly when furnaces, space heaters, and generators misbehave. Who it is for: any home that needs one alarm per floor without wiring work.
Cars and travel: a portable alarm. The Kidde Portable Carbon Monoxide Detector (AA Battery, Travel-Ready) costs about $25 with a 4.5 star rating, runs on AA batteries, and is light enough to ride in a glove box or trunk and sample cabin air while the engine runs for heat. Idling a car for warmth during a stranding or an outage is a classic CO death, and a portable alarm is the only detector that follows you into the car. Who it is for: drivers, renters, and anyone who sleeps anywhere with a furnace they do not own.
Gas-heated homes: the combo alarm. The Kidde Plug-In Explosive Gas & Carbon Monoxide Alarm plugs into a wall outlet at about $57 with a 4.6 star rating, alarms for propane, natural gas, and methane plus CO, and shows a digital readout with a 9-volt backup for outages. A CO alarm alone will not warn for a raw gas leak, so gas households want both layers. Who it is for: homes with gas furnaces, stoves, water heaters, or fireplaces.
| Pick | Price | Rating | Best for |
|---|---|---|---|
| Battery CO alarm | ~$24 | 4.7 | One per floor, no wiring |
| Portable CO alarm | ~$25 | 4.5 | Cars, travel, rentals |
| Plug-in gas plus CO combo | ~$57 | 4.6 | Gas-heated homes |
Generators deserve their own sentence because they kill the most people the fastest. Run them outside, 20 or more feet from doors and windows, never in a garage, even with the door open. Our power outage survival guide covers the full generator rules plus fuel storage. Heating season brings the slower version of the same risk through cracked heat exchangers and unserviced furnaces, which is why our home winterizing checklist starts with a furnace service and fresh detector batteries. And if you heat with gas, learn the difference between the two alarms in our gas leak guide: a CO alarm will not warn for raw natural gas.
Quick recommendations
- Starting from zero: buy one battery alarm per floor and mount them this weekend, bedrooms first.
- Attached garage or gas appliances: add the plug-in combo alarm near the sleeping hallway on the appliance level.
- Winter drivers: put the portable alarm in the car kit before the first freeze.
- Already alarmed: check the date on the back of each unit and replace anything past end of life.
Detector placement checklist
- One CO alarm on every level, basement included
- Alarm outside each sleeping area, audible through closed doors
- 5 to 20 feet from furnace, water heater, fireplace, and stove
- Nothing in the garage, kitchen, humid bathroom, or dead-air corners
- Generator spot picked: outside, 20-plus feet from doors and windows
- Test button pressed monthly, vents vacuumed, batteries fresh
- Install date written on each unit, expired units replaced
A detector is a twenty-five dollar device that covers a failure mode you cannot smell, see, or wake up from. Mount them this weekend and the next outage gets a lot less dangerous.
Frequently asked questions
Where should carbon monoxide detectors be placed in a two-story house?
Put one on every level, including the basement: outside each sleeping area, and 5 to 20 feet from the furnace, water heater, or fireplace. A two-story house with a basement needs at least three. Add one in the garage-adjacent hallway if the garage attaches to the house.
How many carbon monoxide detectors do I need?
At minimum, one per floor, including the basement. Then add coverage so every sleeping area has an alarm within hearing distance outside its door. Large floor plans and homes with fuel-burning appliances on multiple levels need more than the minimum.
Should a carbon monoxide detector go high or low on the wall?
Follow the instructions in the box. Carbon monoxide mixes with room air, so most manufacturers allow wall or ceiling mounting, and plug-in models sit at outlet height. The room you choose matters far more than the exact height: outside bedrooms and set back from appliances beats a perfectly measured bad location.
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