The symptoms of carbon monoxide poisoning are: first, mild poisoning. Patients may have headache, dizziness, insomnia, blurred vision, tinnitus, nausea, vomiting, general fatigue, tachycardia and transient fainting. The content of carboxyhemoglobin in blood is 10%-20%. The second is moderate poisoning. In addition to the above symptoms, lips, nails, skin and mucous membrane appear cherry red, sweating, blood pressure rises first and then falls, heart rate increases rapidly, arrhythmia, irritability, temporary separation of feeling and action (that is, thinking but unable to act). Symptoms continue to worsen, and drowsiness and coma may occur. Carboxyhemoglobin in blood is about 30%-40%. After timely rescue, you can wake up quickly, generally without complications and sequelae. The third is severe poisoning. The patient soon fell into a coma. At the beginning, the muscle tension of limbs increased, or paroxysmal tonic spasm appeared; In the later stage, the muscle tension decreased obviously, the patient's face was pale or blue, blood pressure dropped, pupils dilated, and finally he died of respiratory paralysis. Survivors after rescue may have serious complications and sequelae. Sequela of carbon monoxide. Moderate and severe poisoning patients have neurasthenia, tremor paralysis, hemiplegia, hemianopia, aphasia, dysphagia, mental retardation, toxic psychosis or encephalomyelitis. Some patients may have secondary encephalopathy.