The severe forms are translated by neurological disorders even a coma or the death straight away. The more insidious forms with a little carboxyhémoglobine level give rise to frustrate clinical pictures, mimicking flu or intestinal syndromes. The syndrome post--intervallaire corresponds to the appearance of remote neuropsychiatric disorders of the poisoning. Its appearance and its gravity are not correlated in the gravity of the initial poisoning, however the precocity of the treatment tends to decrease its frequency.