Abstract: Disclosed is an air supply apparatus for open pit incineration for supplying a curtain or layer of combustion air into an open pit. A plenum is provided for being positioned alongside of the pit and a fan and conduit provide air to the plenum. An elongate nozzle directs air from the plenum into the pit in a curtain or layer. Means are provided for selectively exhausting air from the conduit to adjust the volume of air being directed by the nozzle into the pit. Also disclosed is a secondary air supply for air curtain incineration in permanent or semi-permanent pits having walls provided by refractory panels. The plenum and nozzle are positioned adjacent one wall to direct the air curtain so that it primarily impinges upon an opposite wall. The secondary air supply introduces air into the pit at the wall adjacent to the plenum.