Carbon monoxide detectors activate between 70 and 400 parts per million (ppm) of CO in the air. Most residential units trigger alarms at 70 ppm after 1 hour, 150 ppm after 15 minutes, or 400 ppm within 4 minutes.
CO detectors contain sensors that measure CO concentration over time. They use electrochemical, biometric, or metal oxide semiconductor technologies. The device compares readings against preset thresholds to determine if dangerous levels are present.
| Type | Activation Threshold | Response Time |
|---|---|---|
| Biomimetic | 70 ppm | 1 hour |
| Electrochemical | 70 ppm | 1 hour |
| Metal Oxide Semiconductor | 150 ppm | 15 minutes |
CO detectors are required in homes with fuel-burning appliances. They're typically installed near bedrooms and on every floor. The Consumer Product Safety Commission reports that CO poisoning causes 150 deaths annually in the U.S., making these devices critical for safety.
Many people confuse CO detectors with smoke alarms. Unlike smoke alarms, CO detectors don't detect flames or smoke-they only measure invisible, odorless carbon monoxide gas. Another misconception is that CO detectors last forever. In reality, they need replacement every 5-7 years.
I once helped a neighbor install a CO detector in their garage. They were surprised to learn that even electric-only homes can benefit from these devices, as attached garages can still allow CO into living spaces.
Detectors should be placed 5 feet from sleeping areas and between 1-15 feet from fuel-burning appliances. The National Fire Protection Association recommends installing them on every level of the home, including basements but excluding attics.
According to the Centers for Disease Control and Prevention, proper placement reduces the risk of CO poisoning. A well-placed detector can provide important early warning before CO levels become life-threatening.
Understanding at what level CO detectors go off is essential for home safety. These devices activate at specific ppm thresholds to provide timely warnings about dangerous carbon monoxide levels. Proper installation and maintenance ensure they function effectively when needed most.