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Carbon monoxide detector: choose it, place it, keep it working

By the Plain Prepper editors. Updated 2026-10-15.

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Quick answer

CPSC says to use carbon monoxide alarms that meet UL 2034, either battery-operated or plug-in and hardwired models with battery backup. Put one on every level of the home and outside sleeping areas; interconnected alarms are best. Keep them out of kitchens and away from fuel-burning appliances and heating vents. Kidde's manual says to test weekly and replace its sealed-battery alarm after 10 years. If an alarm sounds, go outside right away and call 911. Do not look for the source.

Power types: battery, plug-in, sealed 10-year

Type	How it is powered	Watch for
Plug-in with battery backup	Wall outlet, with batteries that keep it working in a power outage	CPSC says plug-in and hardwired alarms should have battery backup
Replaceable battery	AA or similar batteries; can sit on a table or shelf	Battery changes and low-battery chirps
Sealed 10-year battery	Lithium battery sealed inside for the alarm's life	Stays on once activated; replace the whole unit at end of life
Hardwired	Home wiring, installed by a qualified electrician	Should have battery backup; interconnection lets all alarms sound together

Kidde also sells alarms that add indoor air quality monitoring or explosive gas (natural gas and propane) detection. A standard CO alarm does not detect gas leaks; Kidde's manual says CO alarms should not be used to detect natural gas, propane or butane.

Where to put a carbon monoxide detector

• Every level: CPSC and Kidde both say one on each level of the home, plus outside sleeping areas. Kidde's manual explains why: CO in a basement may not reach an alarm upstairs near the bedrooms.
• Only one alarm: Kidde says put it near the bedrooms, not in the basement or furnace room, and make sure it can be heard from every sleeping area.
• Height: CPSC says plug-in receptacles or high on the wall both work. Kidde suggests eye level for alarms with a display, and keeping a tabletop alarm no more than 3 ft from the floor so a fall does not damage it.
• Keep it clear: do not let furniture or curtains cover the vents.

Places to avoid

Kidde's manual and CPSC list spots that cause damage, nuisance alarms or late warnings:

• Kitchens, garages and furnace rooms, and above fuel-burning appliances.
• Within 1.5 m (about 5 ft) of heating or cooking appliances; Kidde recommends 3 m (about 10 ft).
• Near heating vents, flues and chimneys, or ceiling fans, doors and windows.
• Dead air spaces such as the peak of a vaulted ceiling, where CO may not reach the sensor in time.
• Places colder than 32°F or hotter than 104°F (0°C to 40°C), such as attics, crawl spaces, porches and garages.
• Near large deep-cell batteries, whose emissions Kidde says can affect the alarm.

How an alarm decides when to sound

Alarms that meet UL 2034 sound based on both CO level and time. Kidde's manual lists the response window:

CO level	Alarm within
70 ppm	60 to 240 minutes
150 ppm	10 to 50 minutes
400 ppm	4 to 15 minutes

Kidde's data sheet says its alarm will not sound for levels below 30 ppm under UL 2034. CPSC says most people have no symptoms at about 1 to 70 ppm, though some heart patients may get chest pain, and that sustained levels above 150 to 200 ppm can cause disorientation, unconsciousness and death. Kidde's C3010D display shows readings from 30 ppm, so you can see a level before the alarm sounds.

Weekly checks, replacement and what to do on alarm

• Test: Kidde's manual says test weekly. CPSC notes the test button checks the circuit, not the sensor's accuracy.
• Replace: alarms have a set life. Kidde's sealed-battery alarm beeps twice every 30 seconds after 10 years and no longer detects CO; write the install date on its label.
• If it sounds: CPSC says get outside to fresh air, call 911 or the fire department, count heads, and do not go back in until responders say so.
• If it sounds again: have a qualified technician check every fuel-burning appliance, and do not run a faulty appliance until it has been serviced.
• Rules where you live: CPSC notes many states and towns require CO alarms; ask your local building official.

What to look for when you buy

Questions people ask

Where should a carbon monoxide detector be placed?

On every level of the home and outside sleeping areas, per CPSC, away from kitchens, fuel-burning appliances, heating vents and anything that could cover it.

How long do carbon monoxide detectors last?

Check the maker's replacement age; Kidde's sealed-battery alarm signals end of life after 10 years and then no longer detects CO.

Does a carbon monoxide detector detect gas leaks?

No. Kidde says CO alarms should not be used to detect natural gas or propane; use a combination or explosive gas alarm for that.

What should I do if my carbon monoxide detector goes off?

Get outside to fresh air, call 911 or the fire department, and stay out until responders say it is safe, as CPSC advises.

Sources

• Carbon monoxide questions and answers, U.S. Consumer Product Safety Commission
• C3010 and C3010-D carbon monoxide alarm user guide, Kidde
• Sealed battery carbon monoxide alarm with digital display C3010-D data sheet, Kidde
• Choosing a CO alarm that works for you, Kidde
• Plug-in carbon monoxide alarm with battery backup and digital display (CO615), First Alert
• Carbon monoxide plug-in alarm with battery backup (CO606), First Alert

Sources checked 2026-10-15.