Abstract: A brazing oven includes an arrangement employing a gas curtain or barrier to cover the port or opening of the oven whenever the door is opened. The curtain or barrier is formed by a region of flowing conditioned air directed across the opening. The flowing air curtain or barrier prevents gas from exiting the oven interior when the door is opened, and it also serves to replace or replenish any conditioned air which happens to escape from the oven interior. The air curtain or barrier is generated by a ported manifold and supply located either on the oven housing exterior adjacent the opening or inside the oven housing adjacent the opening.