A gas mixer for mixing a first gas and a second gas, having a first, outer gas housing part, having an inlet for the first gas in a longitudinal axis and an inlet for the second gas in a transverse axis, a second, interior gas housing part set into the first gas housing part to form an annular space for a second gas, having a mixing space into which the first gas and the second gas are introduced for mixing. The first and second gas housing parts and the annular space are aligned along the longitudinal axis and the mixing space is aligned cylindrically along the longitudinal axis. A mixing device having a plurality of hollow rods is arranged in the mixing space. A hollow space of a hollow rod is in fluid communication on both sides with the annular space. The number of hollow rods extends transverse to the longitudinal axis and the transverse axis and at least one hollow rod has a plurality of openings for the second gas, so that the hollow space is in fluid communication with the cylindrical mixing space.