Where to put carbon monoxide detectors: on every level of your home, including the basement, and outside or near each sleeping area. Add one inside near the door to an attached garage. Keep alarms at least 15 feet from fuel-burning appliances, test them monthly, and replace them on the maker's schedule.
Carbon monoxide (CO) is a gas you can't see or smell. The CDC calls it a gas that "kills without warning," and says people who are asleep can die from it before they have symptoms. A working CO alarm is how you find out in time. Here is where to put them, how to look after them, and what to do if one goes off.
The U.S. Consumer Product Safety Commission (CPSC), the CDC and the EPA agree on the basics:
Every level. CPSC says to install CO alarms on every level of the home. The EPA adds that this includes the basement, in a central spot in the livable space.
Near sleeping areas. CPSC says outside each separate sleeping area. The EPA says near or inside each sleeping area, and the CDC says near every sleeping area.
By the garage. If you have an attached garage, the EPA says to put an alarm inside the home near the door to the garage, and in rooms over the garage.
Away from fuel-burning appliances. The EPA says to keep alarms at least 15 feet from any fuel-burning appliance, such as a furnace, water heater, gas stove, fireplace or gas dryer.
Linked together. CPSC says interconnected alarms are best: when one sounds, they all sound.
Height and local rules. The EPA says to follow the manufacturer's instructions and your local building codes for exact placement.
Here is how those rules might look in a two-story house with a basement and an attached garage:
Basement: one alarm in a central spot, at least 15 feet from the furnace and water heater.
Main floor: one in a central spot, and one inside near the door to the garage.
Upstairs: one in the hallway outside the bedrooms. If bedrooms are in separate parts of the house, put one outside each sleeping area.
Bonus room over the garage: one in that room.
In a one-level apartment, the same rules apply: at least one alarm near the bedrooms, plus more if sleeping areas are apart. Check your local code and lease too.
Battery or battery backup. CPSC and the CDC recommend battery-operated alarms or alarms with battery backup. If you choose a plug-in alarm, CPSC says to make sure it also has battery backup.
Safety standard. CPSC recommends alarms that meet the UL 2034 safety standard. Look for it on the package.
Interconnected if you can. A linked alarm in the basement will sound by the bedrooms too.
Every month: press the test button. CPSC and the EPA both say to test CO alarms monthly.
Spring and fall: the CDC suggests checking CO detector batteries when you change your clocks. Replace batteries as the manufacturer recommends.
End of life: CPSC says to replace CO alarms according to the manufacturer's instructions or when the end-of-life signal sounds. The CDC says to follow the manufacturer's instructions or replace them every 5 years.
Write the date: mark the install date on the back of each alarm so you know when it is due.
You need smoke alarms too, and they have their own placement rules. See our guide to smoke alarm placement and testing.
CPSC lists headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion. It notes that at low levels, symptoms can resemble the flu, and at extremely high levels a person can pass out suddenly without milder symptoms first. The EPA says CO can cause flu-like symptoms that clear up after leaving home. If several people at home feel unwell at the same time and feel better away from the house, take it seriously.
The CDC says everyone is at risk, but infants, older adults and people with chronic heart disease, anemia or breathing problems are more likely to get sick from CO.
This is general information, not medical advice. Talk to your doctor or pharmacist about your own situation.
Never ignore it. CPSC is clear on this, even if nobody feels sick.
Get everyone outside to fresh air right away. Bring people and pets out with you.
Call 911 from outside. CPSC says to call from a fresh-air location. If you can't reach 911, call your fire department.
Tell the dispatcher about symptoms. Anyone with a headache, dizziness, confusion or vomiting needs medical help.
Stay out until emergency responders tell you it is safe to go back in.
If you think someone has CO poisoning and there is no alarm, do the same: get to fresh air and call 911.
Yearly service. The CDC says to have your heating system, water heater and any other gas, oil or coal-burning appliances serviced by a qualified technician every year.
No engines indoors. Never run a car or truck in an attached garage, even with the garage door open, the CDC says.
Generators outside only. CPSC says never use a portable generator inside a home or garage, even with doors and windows open. Use it outside, at least 20 feet from the home, with the exhaust pointing away.
Vent the stove. The EPA suggests an exhaust fan vented to the outdoors over gas stoves.
Vented heaters. When replacing an unvented space heater, the EPA suggests considering a vented one.
On every level of the home, including the basement, near or outside each sleeping area, and inside near the door to an attached garage. Keep it at least 15 feet from fuel-burning appliances.
Follow the instructions that came with your alarm and your local building code. The EPA points to both for exact placement.
CPSC recommends CO alarms for every home. CO can also come from an attached garage or a generator used during an outage.
CPSC says to follow the manufacturer's instructions or replace it when the end-of-life signal sounds. The CDC says to follow the instructions or replace it every 5 years.
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