Asphyxiants deprive the body of oxygen. Simple asphyxiants displace oxygen from the lungs, whereas systemic asphyxiants interfere with transport of oxygen by hemoglobin or with mitochondrial oxidative phosphorylation. Asphyxiants may be gases, liquids, or solids, or their metabolites. The typical clinical picture of asphyxiant poisoning is one of progressive mental status changes, alteration of breathing, progressively abnormal vital signs, coma, seizures, and eventually cardiovascular collapse and death. Treatment of asphyxiant poisoning is aggressive supportive care, with control of the airway and ventilation and maintenance of cardiac output. Supportive care is often enhanced by the administration of specific antidotes.