PROBLEM TO BE SOLVED: To provide a system for administering carbon monoxide, capable of more safely administering carbon monoxide to a patient.SOLUTION: In a system 10 for administering carbon monoxide to a patient to treat the patient from disease, a mixing section 41 mixes oxygen supplied from an oxygen supply section 20 with carbon monoxide supplied from a carbon monoxide supply section 30, and discharges a mixed gas to be administered to the patient. A section 42 adjusts and cuts off the flow rate of carbon monoxide supplied to the mixing section 41. A carbon monoxide concentration sensor 43 detects the concentration of the carbon monoxide in the mixed gas. A controller 62 controls the section 42 to adjust the concentration of the carbon monoxide administered to the patient on the basis of the detected concentration of the carbon monoxide. When the concentration of the carbon monoxide shows an abnormal value, the controller gives an alarm via an alarm 64 and controls the section 42 to cut off the carbon monoxide administered to the patient.
