The deplumer prevents steam plumes generated from H2O vapor saturated gas when it is discharged into the atmosphere. This device can be also used in many other processes for the prevention of steam plumes. H2O vapor saturated gas is sent to a heat exchanger and cooled by air that is fed by a fan. Subsequently, steam in the combustion gas is condensed through heat exchange. Cooled combustion gas and heated air are mixed in the stack and discharged into the atmosphere without the formation of plumes.