A gas mixer (10) for mixing a first gas stream with a second gas stream includes an impact labyrinth (24) in the first gas stream having structures (25), e.g., corrugated walls, forming a tortuous path through which the first gas stream must pass en route to a mixing point (20) in the gas mixer. The labyrinth fosters ignition of particles entrained in the first gas stream. Elongate, straight pipes (30) receive the first gas stream from the impact labyrinth (24) and carrying the first gas stream to the mixing point (20) the pipes (30) are positioned with a vessel (12) carrying the second gas stream. The pipes (30) have openings which are substantially aligned with the flow direction of the second gas stream at the mixing point (20) thereby introducing the first gas stream into the second gas stream in a low shear manner.