Best carbon monoxide alarms

How to choose

Buy a listed alarm with an electrochemical sensor

Any working listed alarm beats none. In a review of 408 Wisconsin poison center cases that mentioned a detector, the odds of poisoning were 3.2 times higher with no detector than with one that sounded.¹⁶

CPSC tells you to buy an alarm that meets the current UL 2034.¹ Look for the mark on the alarm itself, and buy a known brand from a known seller. In 2017, Consumer Reports labeled three off-brand alarms sold online (Foho, GoChange and NetBoat) Don't Buy: Safety Risk, and none carried UL certification. The UK consumer group Which? says every unbranded alarm it has tested failed.^{17 18}

Then check the data sheet for the sensor, because the box may not say. CPSC staff bought 102 alarms, 17 each of six models, and put them through 21 test scenarios. The semiconductor and biomimetic models each had eight potentially hazardous failures, and the four electrochemical models together had six failures of any kind.^{2 19} Those alarms were built in 2011 and 2012 and the models were anonymous, so this favors a sensor type and not a brand.

Make sure it works when the power goes out

This matters most. CPSC recommends battery-operated alarms or alarms with battery backup.¹ Generators, which run during outages, are tied to an estimated 892 CO deaths from 2012 to 2022, 41 percent of the non-fire CO deaths linked to consumer products.²⁰ In New York, a study of 917 children's cases found that four hours without power raised the odds of an emergency visit by at least 50 percent.²¹ After a 2002 ice storm in Mecklenburg County, North Carolina, 96.2 percent of severe poisonings were in homes with no reported working alarm.²²

So avoid plain plug-ins. First Alert's manuals also say the backup battery isn't meant to run a plug-in for an extended time, so keep it fresh, and add a battery-powered alarm such as the COB if an outage could run long.^{4 10} A home that's all electric still needs an alarm if you might run a generator, and CPSC said in 2001 that every home should have at least one.^{20 23}

Don't overpay for a display

CO is measured in parts per million, or ppm. A display shows CO from 30 ppm up, because UL 2034 says it must show nothing lower. Readings need only be accurate to within 30 percent.²⁴ Peak memory can record lower levels on some models; Kidde says the C3010-D stores peaks as low as 11 ppm.²⁵ First Alert's CO3-P01D manual says that alarm typically isn't made to detect CO below 30 ppm.⁴

Don't trust a quiet alarm

Listed alarms are built to stay quiet at low levels. Under UL 2034, an alarm must sound within 60 to 240 minutes at 70 ppm, 10 to 50 minutes at 150 ppm and 4 to 15 minutes at 400 ppm, and it must not sound at 30 ppm for 30 days.²⁴ CPSC staff say pregnant women, young children and people with heart disease are more likely to have effects at levels these limits allow.²⁴

If the alarm sounds, move everyone to fresh air and call 911.¹⁰ If you suspect CO because of headaches, fatigue or nausea, don't take a quiet alarm as an all-clear. Leave the house, call for help and have your appliances checked.^{10 24}

If someone at home has heart or lung disease, is pregnant or is an infant, consider a listed alarm with low-level alerts. Kidde says its COBDL and COBDL10 alert within 21 minutes at 70 ppm, where the main alarm may take up to 240 minutes.¹⁴ Ask a doctor whether a monitor that reads below 30 ppm makes sense too. For most homes, a low-level device is a reasonable extra and not a proven need. A 2024 petition asks CPSC for lower alarm levels, and CPSC staff say a 2026 review questioning the current levels doesn't alone show a significant hazard.^{24 26}

Buy gas detection separately

Kidde's manual puts natural gas alarms high on the wall, propane alarms near the floor, and explosive gas alarms where fuel-burning appliances are. A CO alarm belongs near bedrooms and at least 6 feet from those appliances, so one box can't fully do both jobs.²⁷ Kidde's COPDLG also lasts 7 years, against 10 for its CO-only plug-ins, and Kidde warns that silicone vapors can permanently reduce its sensor's sensitivity.^{12 27 28} We know of no independent test of how well home gas alarms catch leaks.

Put one on every level, bedrooms first

You need at least one CO alarm on every level and one outside each sleeping area, and the bedroom areas come first.¹ In a review of 136 New Mexico deaths, about half of those who died at home were probably asleep, and the authors estimated that detectors may have prevented about half of the deaths.²⁹ Homes fall short on this: in a Washington State survey, only half to two-thirds of equipped homes had enough alarms.³⁰ You can count combo alarms toward your total.

CPSC says to use an outlet or mount the alarm high on the wall, away from vents and furniture, and not in kitchens or above fuel-burning appliances.¹ Kidde adds garages and a 6-foot gap from heating and cooking appliances.²⁷ First Alert's manuals are stricter, at 15 feet from a furnace for the CO3-P01 and 20 feet where possible for the CO3-P01D, so follow your model's manual.^{4 10} Height matters less for CO, which Kidde says disperses evenly.³¹

Basements are the one point of conflict. CPSC's fact sheet says every level, while its CO Alarms page says to skip attics and basements with no sleeping area. Kidde recommends each level but says a single alarm belongs near bedrooms.^{1 13 27 32} Cover the bedrooms first. One in a furnace basement is a reasonable addition if you keep the manual's distance from the furnace, and First Alert's CO3-P01 manual puts it at the top of the basement stairs.¹⁰ The basement still needs its own smoke alarm, which our smoke alarm guide covers.¹³

CPSC calls interconnected alarms, which all sound when one does, the best choice.¹ None of the picks here can link, so see our combo alarm guide if you want that.

Test it, and write down the replace-by date

Test at least monthly, and weekly if you buy either First Alert pick, because both manuals say so.^{4 10 13} Homes often skip this: in a 2025 English survey of 6,043 emergency patients, only 57 percent had alarms placed correctly and 21 percent had never tested them.³³

Write the replace-by date on the alarm. UL 2034 sets only a 3-year minimum, so life varies: Kidde's current CO-only models say 10 years, its gas models say 7, and First Alert's CO3-P01 and CO3-P01D manuals say 7.^{4 10 12 24 28} When the end-of-life signal starts, replace the alarm. Kidde's KN-COEG-3 guide says it won't detect CO in that state.³²