Abstract: Device for adding secondary air to a converter structure including a converter housing with inlet and outlet structures attached to opposite ends thereof. A pair of catalyst containing beds are supported within the housing in spaced relationship. The improved device for introducing secondary air in the space between the spaced catalyst containing beds includes structure for forming a restricted throat between the spaced catalyst containing beds and structure forming an annular zone between the structure and the interior surface of the converter housing. The annular zone encircles the restricted throat and is connected thereto by a plurality of openings. A secondary air supply supplies air to the annular zone which can flow through the openings to the restricted throat.