We know that carbon monoxide (CO) is dangerous. We also believe that CO alarms will alert us to dangerous levels of CO. But a study conducted in 2011 of residential carbon monoxide alarms found that more than half failed to function correctly, alarming too early or too late. Forty percent of detectors failed to alarm in hazardous concentrations, despite outward indications that they were operating as intended. The study’s sample size was extremely small, but the implications are enormous, and the opportunity to protect your customers is tremendous.