An air conditioner in which flammable refrigerant circulates in order of a compressor, a first heat exchanger, an expansion valve, and a second heat exchanger, the compressor being configured to store refrigeration oil and discharge the refrigeration oil with the refrigerant, the refrigeration oil circulating with the refrigerant in order of the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger, the first heat exchanger being located in a first space, the second heat exchanger being located in a second space, the air conditioner comprising: a first sensor configured to detect the refrigerant in the first space; a second sensor configured to detect an odor of the refrigeration oil in the first space; and a controller configured to detect a leak of the refrigerant using a first detection signal from the first sensor and a second detection signal from the second sensor, wherein the controller is configured to detect a leak of the refrigerant when the first detection signal is greater than a first threshold, when the second detection signal is greater than a second threshold, and when the first detection signal is greater than a third threshold and the second detection signal is greater than a fourth threshold, wherein the first sensor is configured to be supplied with electric power from a first power supply, the second sensor is configured to be supplied with electric power from a second power supply, the controller is configured to be supplied with electric power from the first power supply, and the second sensor is configured to notify a leak of the refrigerant when the second detection signal exceeds the second threshold (B 1). the compressor being configured to store refrigeration oil and discharge the refrigeration oil with the refrigerant, the refrigeration oil circulating with the refrigerant in order of the compressor, the first heat exchanger, the expansion valve, and the second heat exchanger, the first heat exchanger being located in a first space, the second heat exchanger being located in a second space, the air conditioner comprising: a first sensor configured to detect the refrigerant in the first space; a second sensor configured to detect an odor of the refrigeration oil in the first space; and a controller configured to detect a leak of the refrigerant using a first detection signal from the first sensor and a second detection signal from the second sensor, a first sensor configured to detect the refrigerant in the first space; a second sensor configured to detect an odor of the refrigeration oil in the first space; and a controller configured to detect a leak of the refrigerant using a first detection signal from the first sensor and a second detection signal from the second sensor, wherein the controller is configured to detect a leak of the refrigerant when the first detection signal is greater than a first threshold, when the second detection signal is greater than a second threshold, and when the first detection signal is greater than a third threshold and the second detection signal is greater than a fourth threshold, wherein the first sensor is configured to be supplied with electric power from a first power supply, the second sensor is configured to be supplied with electric power from a second power supply, the controller is configured to be supplied with electric power from the first power supply, and the second sensor is configured to notify a leak of the refrigerant when the second detection signal exceeds the second threshold (B 1).