How to Test a Carbon Monoxide Detector

Carbon monoxide and smoke detector attached to the ceiling.
  • 1-2 hours
  • Beginner
  • 0-300
What You'll Need
Carbon monoxide detectors
Substances that emit low levels of CO
Carbon monoxide testing kits

Knowing if your carbon monoxide detector is working properly is a serious matter. You must test a carbon monoxide detector to ensure it can identify the level of carbon monoxide (CO) in the air, measured in parts per million (ppm). Pressing the 'Test' button on the detector will only tell you whether the device has adequate electrical power from an outlet or batteries. Follow the guidelines below to test your carbon monoxide detectors for accuracy in detecting a poison in your home that can be lethal.

Step 1 - Install the Carbon Monoxide Detectors Correctly

Make sure all your carbon monoxide detectors are correctly installed, at least one per floor of your house, and more than 10 feet from carbon monoxide sources.

Step 2 - Test Each CO Detector for Proper Function

Press the 'Test' button on each CO detector to ensure it is drawing electrical power. It will emit high-pitched, loud beeping, usually louder than a smoke detector.

Step 3 - Test Digital Readout CO Detectors With a Low Level CO Source

To confirm that a digital readout CO detector is detecting carbon monoxide, test it with a substance that will emit low levels of the gas, such as a lit cigarette or a lit incense wand. As you move the cigarette or wand within eight inches of the CO detector, the digital display should change to register the presence of carbon monoxide. If the CO level detected is below 70 parts per million (ppm) the alarm will probably not go off. Should you have small children or people with respiratory problems living in your home, a level as low as 30 ppm can make them feel ill. Be sure to install at least one digital readout CO detector in your home.

Step 4 - Use a Carbon Monoxide Detector Test Kit

Carbon monoxide detector test kits can be purchased where you buy your CO detector. They include a small container full of gas at a high CO concentration, usually up to 1000 ppm, and a plastic housing that you put around the detector for the test. The alarm will certainly sound during this test, so be prepared. However, this test proves only that your carbon monoxide detector will respond to a CO level well beyond the lethal range.

Step 5 - Know When Your Carbon Monoxide Detector Will Sound an Alarm

A CO detector approved by UL, the Underwriters Laboratory, will sound an alarm when concentrations of CO reach 70 ppm and remain steady for one to four hours. The alarm must sound within 10 minutes to one hour of constant CO levels of 150 ppm. At 200 ppm, the alarm must activate within half an hour. Your CO alarm must buzz within 15 minutes of a CO level of 400 ppm. An air concentration of CO above 400 ppm will be fatal within three hours.

Never ignore a carbon monoxide alarm, even if you're unsure of whether the alarm is valid. Get everyone in the house outside, and open all the windows near the detector to reduce the CO concentration in the air. Call 911 for emergency services and contact your local gas company.