A device for cooling a gas is provided. The device comprises an inlet having a first diameter, a mixing section downstream of the inlet and having a second diameter, and an opening in fluid communication with the mixing section and a source of air. The device is such that the second diameter is smaller than the first diameter and a vacuum is created for drawing in the air from the opening as gas passes from the inlet to the mixing section so that the air drawn into the mixing section mixes with the gas. A method for mixing two gases and an exhaust system are also provided.