How to test carbon monoxide alarm?

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. read more

To test a carbon monoxide detector, hold down the “test” button until you hear two beeps sound off. Once you hear these beeps, release your finger off of the test button. Recreate this event, but this time hold down the test button until you hear four beeps. read more