An air conditioning system comprising: an air conditioner configured to generate conditioned air by heat exchange with a refrigerant and supply the conditioned air to an air conditioning target space; a refrigerant sensor configured to detect refrigerant leakage; a ventilator configured to ventilate the air conditioning target space; and a controller configured to control the ventilator, wherein the ventilator includes: a total heat exchanger; a first air supply path and a first air exhaust path configured to allow an inside and an outside of the air conditioning target space to communicate with each other via the total heat exchanger; characterized in that the ventilator further comprises: a second air supply path configured to allow the inside and the outside of the air conditioning target space to communicate with each other without passing through the total heat exchanger; an air supply fan configured to supply air outside the air conditioning target space into the air conditioning target space via the first air supply path and the second air supply path; an air exhaust fan configured to discharge air in the air conditioning target space to the outside of the air conditioning target space via the first air exhaust path; and an air supply opening-closing mechanism configured to open and close by switching between the first air supply path and the second air supply path, and the controller controls the air supply opening-closing mechanism to open the second air supply path when the refrigerant sensor detects refrigerant leakage. an air conditioner configured to generate conditioned air by heat exchange with a refrigerant and supply the conditioned air to an air conditioning target space; a refrigerant sensor configured to detect refrigerant leakage; a ventilator configured to ventilate the air conditioning target space; and a controller configured to control the ventilator, wherein the ventilator includes: a total heat exchanger; a first air supply path and a first air exhaust path configured to allow an inside and an outside of the air conditioning target space to communicate with each other via the total heat exchanger; characterized in that the ventilator further comprises: a second air supply path configured to allow the inside and the outside of the air conditioning target space to communicate with each other without passing through the total heat exchanger; an air supply fan configured to supply air outside the air conditioning target space into the air conditioning target space via the first air supply path and the second air supply path; an air exhaust fan configured to discharge air in the air conditioning target space to the outside of the air conditioning target space via the first air exhaust path; and an air supply opening-closing mechanism configured to open and close by switching between the first air supply path and the second air supply path, and the controller controls the air supply opening-closing mechanism to open the second air supply path when the refrigerant sensor detects refrigerant leakage. a total heat exchanger; a first air supply path and a first air exhaust path configured to allow an inside and an outside of the air conditioning target space to communicate with each other via the total heat exchanger; characterized in that the ventilator further comprises: a second air supply path configured to allow the inside and the outside of the air conditioning target space to communicate with each other without passing through the total heat exchanger; an air supply fan configured to supply air outside the air conditioning target space into the air conditioning target space via the first air supply path and the second air supply path; an air exhaust fan configured to discharge air in the air conditioning target space to the outside of the air conditioning target space via the first air exhaust path; and an air supply opening-closing mechanism configured to open and close by switching between the first air supply path and the second air supply path, and the controller controls the air supply opening-closing mechanism to open the second air supply path when the refrigerant sensor detects refrigerant leakage. a second air supply path configured to allow the inside and the outside of the air conditioning target space to communicate with each other without passing through the total heat exchanger; an air supply fan configured to supply air outside the air conditioning target space into the air conditioning target space via the first air supply path and the second air supply path; an air exhaust fan configured to discharge air in the air conditioning target space to the outside of the air conditioning target space via the first air exhaust path; and an air supply opening-closing mechanism configured to open and close by switching between the first air supply path and the second air supply path, and the controller controls the air supply opening-closing mechanism to open the second air supply path when the refrigerant sensor detects refrigerant leakage.