PURPOSE: To prevent explosion of gas and/or abnormal vibration in an engine device equipped with a heat recovery device, by guiding exhaust gas to a gas detector.

CONSTITUTION: Hot water in piping nozzles 4, 5, connected to a load side, is heated by a condenser 3, and a coolant, fed to the condenser 3, is compressed by a compressor 1 driven by a gas engine 2, after combustion exhaust gas from the engine 2 is emitted from a delivery pipe 9 and cooled by an exhaust gas heat recovery device 10, the gas is discharged from a delivery pipe 12, here a long branch pipe 14 is provided to the delivery pipe 9, and gas in the inside is cooled by air in the surroundings, and then the gas is guided to a gas detector 15 to operate a buzzer 16 and the like. In this way, temperature of the gas is decreased to a low level, and a gas detector sold at a market can be used, while uncombustion gas can be promptly detected.