Refrigeration device for container

A container refrigeration apparatus attached to a container in which a breathing plant is housed, the apparatus comprising:

• a refrigerant circuit to which an evaporator that allows air in the container to exchange heat with a refrigerant is connected, and in which the refrigerant circulates to perform a refrigeration cycle;
• and
• an inside air control system which has:
• a gas supply device having a supply passage which communicates with an inside of the container and through which supply air is supplied into the container;
• and an oxygen sensor which measures an oxygen concentration of the air in the container, the inside air control system controlling the oxygen concentration of the air in the container to be a target concentration, wherein
• a supply state of the gas supply device is switched between a first supply state of producing, from outside air, nitrogen-enriched air having a higher nitrogen concentration and lower oxygen concentration than the outside air, and supplying, as the supply air, the nitrogen-enriched air into the container, and a second supply state in which the gas supply device takes outside air therein and supplies, as the supply air, the outside air into the container,
• the inside air control system has
• a branch pipe which is connected to the supply passage and guides at least part of the supply air flowing through the supply passage to the oxygen sensor, and
• an open/close valve which opens/closes the branch pipe, and
• the inside air control system performs an outside air calibration operation in which the open/close valve is opened in the second supply state, and the at least part of the outside air flowing through the supply passage is guided to the oxygen sensor to calibrate the oxygen sensor using the outside air.