What levels (ppm) of carbon monoxide cause an alarm?

Carbon monoxide alarms are designed to alarm before the average healthy adult feels symptoms.

Since you cannot see or smell CO, never assume it's not present.

Underwriters Laboratories Inc. Standard UL2034 requires residential CO alarms to sound when exposure times and exposure levels of CO in the chart below. CO alarm levels are measured in parts per million (ppm) of CO over time (in minutes). The UL2034 Required Alarm Points are:

  • If the Alarm is exposed to 400 ppm of CO, it must alarm between 4 and 15 minutes.
  • If the Alarm is exposed to 150 ppm of CO, it must alarm between 10 and 50 minutes.
  • If the Alarm is exposed to 70 ppm of CO, it must alarm between 60 and 240 minutes.

The alarm is designed not to alarm when exposed to a constant level of 30 ppm for a period of 30 days.

« Back To FAQs List