Where to place carbon monoxide detectors

Why placement matters

Carbon monoxide (CO) is a colorless, odorless gas made when fuel burns incompletely. The CPSC reports that more than 200 people in the United States die every year from accidental non-fire CO poisoning linked to consumer products, and more than 100 of those deaths involve portable generators. Symptoms such as headache, dizziness, weakness, nausea and confusion are easy to mistake for the flu. An alarm is the only way most people will know, especially while asleep, so it has to be where it will wake you.

The basic rule: every level and outside sleeping areas

CPSC advice: install battery-operated CO alarms, or alarms with battery backup, on every level of the home and outside sleeping areas. In practice that means:

The first two rows come from CPSC’s rule; the last two are common sense for homes with a garage or a fuel-burning appliance, and the alarm’s manual may add distances.

Spots to avoid

• Next to a heating vent or air supply, where moving air may affect readings.
• Behind furniture or curtains that could cover the alarm.
• Directly above a fuel-burning appliance or in an area with a lot of steam, such as inside a bathroom, unless the maker says it is allowed.
• Outdoors, in a vented garage or in a damp crawlspace unless the alarm is rated for it.

The maker’s manual decides the final height. CPSC says alarms can be plugged in or mounted high on a wall, so do not assume a ceiling spot is right for your model.

Battery backup and the type of alarm

CPSC recommends alarms with battery backup, so the alarm keeps working in a power outage, exactly when people run generators and fuel-burning heaters. Pick an alarm listed to UL 2034, the standard UL Solutions describes as covering single and multiple station CO alarms; CPSC says to install an alarm that meets the current UL 2034 standard. Combination smoke and CO units meet both UL 217 and UL 2034, which saves ceiling space; see wireless interconnected smoke alarms.

Sources you can control

• Generators: CPSC says to use generators outside only, at least 20 feet from the home, with the exhaust facing away. Never run one inside a home or garage, even with the doors and windows open.
• Cars: never leave a car running in an attached garage, even with the garage door open.
• Heating system: have it professionally inspected and serviced every year; the U.S. Fire Administration makes the same annual-inspection point for heating equipment and chimneys.
• Gas appliances and water heaters: have a licensed professional repair them. Do not tinker with gas lines or venting yourself.

Testing, lifespan and replacement

CPSC notes that pressing the test button checks that the circuitry works, not the accuracy of the sensor. Test it as the manufacturer instructs, check the batteries regularly and replace the alarm at its recommended replacement age, which is printed on the alarm or given in the manual. CO sensors wear out, and many alarms chirp or show an end-of-life message. Write the replacement date on the alarm when you install it. A full shopping list for a three-bedroom home is in the smart smoke and CO alarm kit; for kitchen false alarms, see smoke alarm near the kitchen. For a home with smart alerts, FTC basics apply: unique password and two-factor authentication on the account.

If the alarm sounds

CPSC says that if you suspect CO poisoning you should get to fresh air right away and then call 911. Do not go back in to look for the source. Open the door, leave, and call. Have the equipment checked by a professional before using it again.