Accidental carbon monoxide (CO) poisoning affects approximately 1,000 households and more than 3,000 people each year. To identify the factors contributing to these poisonings, a joint survey by the National Institute for Prevention and Health Education and the French Institute for Public Health Surveillance was conducted by telephone with 500 individuals who were the primary contacts for households affected by poisoning. More than half of the respondents reported that they were “fairly uninformed” or not informed about CO prior to the incident. This lack of information was more prevalent among the least advantaged socioeconomic groups. Despite an awareness of the dangers of CO and knowledge of the main appliances and fuels that emit this gas, only 38% of those surveyed believed they had equipment in their homes that posed a risk of CO emissions prior to the incident (29% among the least informed). At the time of the incident, 61% of respondents present had not made the connection between the observed symptoms and the presence of CO in the home (72% among the least informed). Our results also showed that a high level of information was associated with better preventive behaviors (maintenance and emergency actions). It therefore appears necessary to strengthen communication through an approach that is both universal and targeted, by engaging as closely as possible with users.