Test CO detectors

Test your CO detectors to ensure they'll warn you of this invisible, odorless danger

Why it matters#

Carbon monoxide is colorless and odorless—you can't detect it without a working alarm. CO poisoning sends 50,000+ Americans to the ER annually and causes 400+ deaths.

What you'll need#

Tools#

• Step stool or ladder (if needed)

Materials#

• AA batteries or 9V battery (have on hand for replacement)

Steps#

1. Notify your household#

Let everyone know you're testing. CO detector alarms sound different from smoke detectors—typically 4 beeps in a pattern.

2. Locate all CO detectors#

There should be one on each level of your home, especially near sleeping areas and attached garages. They're often combined with smoke detectors.

3. Press and hold the test button#

Hold for 3-5 seconds until you hear the alarm. CO detectors typically beep 4 times, pause, then repeat. A weak or absent alarm means replace batteries immediately.

4. Check the expiration date#

CO detectors expire after 5-7 years (check the label). Unlike smoke detectors, the sensor degrades and cannot be fixed—replacement is required.

5. Verify proper placement#

CO detectors work best at knee-to-chest height since CO mixes with air. Avoid placing within 15 feet of fuel-burning appliances to prevent false alarms.

6. Replace batteries if needed#

Even plug-in or hardwired units have backup batteries. Replace them annually or immediately if the low-battery chirp sounds.

Pro tips#

• Test monthly along with your smoke detectors
• Know your alarm patterns: 4 beeps = CO detected, 1 chirp every 30-60 seconds = low battery, 5 beeps = end of life
• If the alarm sounds for real, get everyone outside immediately and call 911—don't try to find the source
• Combination smoke/CO detectors are convenient but must be replaced on the shorter CO timeline (5-7 years)

Warnings#

• Never ignore a CO alarm—even if you feel fine, CO poisoning symptoms are subtle
• Don't place CO detectors in garages, kitchens, or near fuel-burning appliances (causes false alarms)

When to call a pro#

If your CO alarm goes off, evacuate and call 911. Have your HVAC system, water heater, and fuel-burning appliances inspected before returning home.