The First Alert OneLink CO511B is part of the Smoke & Carbon Monoxide Detectors test program at Consumer Reports. In our lab tests, Smoke & Carbon Monoxide Detectors models like the OneLink CO511B are rated on multiple criteria, such as those listed below.

High CO levels: High CO levels rates a model's response to CO of 300 parts per million.

Low CO levels: Low CO levels rates a model's response to CO of 150 ppm.

Display/voice: Display/voice rates the accuracy of the CO level either displayed digitally or conveyed by voice message.