Inclusion Criteria:  ≥ 19 years. Patients who received HBO within 24 hours for acute CO poisoning. Patients who meet the definition of ASCOP (Patients incapable verbal obey after HBO). Signed informed consent prior to study entry.  Exclusion Criteria:  Cardiac arrest before HBO Previous neurocognitive disorders Life-threatening underlying disease (ex: advanced cancer) Evidence of co-ingestion of sedative or hypnotics confirmed by intravenous flumazenil administration or history taking at the emergency department Absolute contraindication for TH (active severe bleeding and profound shock not controlled by vasoactive drugs) No admission The significant co-ingested drug levels, which are alter the consciousness, is confirmed from the drug analysis lab Pregnancy Burns More than moderate burn or Inhalation burn Burns complicated by other trauma Electrical burn Burns in high risk patients (Patients with chronic underlying diseases (i.e DM, ESRD, liver cirrhosis, etc) which may cause delays or aggravate the wound healing)