Abstract: A gas mixer for mixing two or more gases of different quantities and physical characteristics includes a gas inlet chamber and a gas mixing chamber in gaseous communication with the gas inlet chamber. Pairs of gas inlet ducts face one another across the gas inlet chamber so that the gas streams emitting from the inlet ducts interfere causing intermingling of the gases. From the inlet chamber the gases flow downwardly into a mixing chamber. A clean air inlet duct extends across the mixing chamber. The clean air inlet duct has a longitudinal slot with a cusp shaped baffle disposed in the slot. Clean air exits the clean air inlet duct through the slot past the baffle and into the gas mixing chamber where it mixes with the gases from the inlet chamber. The mixture of gas then flows out of the mixing chamber, past rectifying vanes which change the gas flow from turbulent to laminar, and into an exhaust duct.