Introduction - Awareness of the risks associated with carbon monoxide (CO) was assessed in a public housing complex in Morbihan. The study sought to identify differences in awareness between tenants equipped with CO detectors and those who were not. Methods - The survey, conducted from September 24 to October 19, 2007, was based on a two-stage random sampling method involving the selection of households, stratified by the presence of a detector in the dwelling, followed by the selection of tenants. Results - The gaseous nature of CO was identified by 89.3% of tenants. Among tenants without a detector, 45.4% knew that CO is not detectable by the senses and 97.5% knew that it can cause health effects. Among these, 39.6% were well aware of the nature of these effects. No significant differences were found between the two groups regarding knowledge of CO sources, effects, risks, and means of preventing CO poisoning. However, the presence of a detector in the home and a history of alarms were associated with greater awareness that CO is undetectable by the senses (+21% and +41%). Conclusion - The results suggest that the presence of CO detectors improves awareness of the fact that CO is undetectable by the senses. (R.A.)