A curing apparatus comprises a curing chamber for accommodating a controlled atmosphere for a product being treated and an irradiator for providing radiation directed at the product. The curing chamber has spaced inlet and outlet openings for the product establishing a path of travel underneath the irradiator. First and second nozzle assemblies are disposed adjacent respective inlet and outlet openings for supplying inert gas into the chamber and maintaining an inert atmosphere within the chamber. The nozzle assemblies are removably secured to the chamber. A pre-chamber is provided in the nozzle assemblies to moderate the pressure distribution of the gas within the nozzle assemblies.