The objective of this study was to describe changes in carbon monoxide (CO) safety knowledge and observed CO detector use following distribution of a CO detector use intervention in two environments, a pediatric emergency department (Ohio) and an urban community (Maryland). A total of 301 participants completed the 6-month follow up (Ohio: n = 125; Maryland: n = 176). The majority of participants was female, 25–34 years of age, and employed (full or part time). We found that CO safety knowledge did not differ between settings at enrollment, but significantly improved at the follow-up visits. The majority of CO detectors observed were functional and installed in the correct location. Of those with CO detectors at follow up, the majority had not replaced the battery. The success of the intervention varied between settings and distribution methods. The majority of participants showed improved knowledge and behaviors. Improved device technology may be needed to eliminate the need for battery replacement.