Ventilator and air conditioning system

A ventilator comprising:

• a refrigerant circuit through which a refrigerant flows and that comprises:
• a compressor, first heat exchangers, and second heat exchangers that are connected by a refrigerant pipe;
• air supply fans that supply air from an outdoor space to an indoor space through the first heat exchangers;
• first casings that accommodate the first heat exchangers and the air supply fans;
• exhaust fans that exhaust air from the indoor space to the outdoor space through the second heat exchangers;
• and
• second casings that accommodate the second heat exchangers and the exhaust fans, wherein
• the first casings are separable from the second casings,
• the first heat exchangers, the air supply fans, and the first casings constitute air supply units,
• the second heat exchangers, the exhaust fans, and the second casings constitute exhaust units, and
• either the air supply units or the exhaust units are connected to the compressor.