An air/burner port assembly for a boiler having a water-wall and a windbox spaced rearwardly of the water-wall to form a windbox, comprises a burner and ignitor mounted in the windbox for directing and igniting fuel through a port in the water-wall. A damper door is mounted on linkages which are actuated by a piston and cylinder combination, for opening and closing the port. The burner comprises an atomizer which is mounted within a fixed sleeve for movement outwardly of the port when the damper is open, and inwardly of the port for allowing the damper to close.