inner door will be closed at all times except when a car is charged into the kiln the outer door will be closed only when the kiln charges a car into the offtake zone the entrance vestibule with at least one door always closed will create an air lock at the kiln entrance to minimize upsetting of the kiln draught during kiln car charging in one example of the invention the kiln includes a preheat zone 24 a furnace zone 26 and a cooling zone 28 the kiln preheat zone 24 is approximately nine and one half 91 2 cars long and is the early heating zone through which the combustion gases from the firing zone are drawn to preheat the load the preheat zone 24 includes a kiln offtake portion 30 of the zone is approximately one and one half 11 2 cars long exhaust gases are drawn from the kiln via wall offtakes above and below load level via insulated stainless steel ductwork to the kiln exhaust fan the kiln exhaust fan will discharge through an exhaust stack to a suitable height above factory roof level the kiln exhaust inlet damper is controlled by an electric motor to automatically control kiln pressure in the firing zone additional control of the preheat zone temperature is accomplished with a series of roof mounted ceramic nozzles or jets 32 in a preferred form of the invention these nozzles 32 are arranged in twenty three rows of six nozzles per row and each row has a butterfly valve for manual control all of the nozzles 32 are located in the roof of kiln in one example of the invention the furnace zone 26 of the kiln is approximately eight cars long and is the heating zone.