Colourless and odourless, each year carbon monoxide is responsible for several thousand cases of poisoning. Often collective, their symptoms are non specific and can result in serious neurological sequelae or even death, if they are not detected in time. The (pre-) hospital emergency nurse plays an important role in the management of these patients, in terms of assessment, treatment and monitoring as well as the organisation of the admittance of victims, categorisation and medical triage. As part of a team, the nurse ensures that the patient enters an adapted, regulated pathway, with the most serious cases being directed towards a hospital equipped with a hyperbaric medicine facility.