Although there are several types of tunnel kilns, the most common are the car tunnel kiln and pusher slab kiln both designed for continuous operations.  The car tunnel kiln uses a train of kiln cars to close the bottom of the kiln.  The ware is loaded onto each kiln care and then pushed into the kiln at the entrance end by the main kiln pusher simultaneously pushing a car out at the exit end of the kiln.  Transfer cars and external return tracks can be manual operation or fully automatic.  This design can be used with natural gas or electric fired to 3000F, the most common fuel being natural gas.  Many systems can be incorporated on a car tunnel kiln such as pre heat an cooling re-circulation fans, quick cooling blowers, waste heat to dryer duct systems, pre heat and cooling exhaust and kiln pressure control.

The pusher slab tunnel kiln incorporates a ceramic heart plate system that conveys ware through the kiln on a ceramic pusher plate.  Operating on the same principal as the car tunnel kiln, as one pusher plate is pushed in the kiln the continuous line pushes a pusher plate out at the exit end.  A closed loop automated return system conveys the ware down a return line for unloading and loading.  The pusher slab tunnel kiln offers atmosphere control with electric heating elements.  This type of kiln is best suited for small technical ceramics an requires design for firing cycle, atmosphere and firing profile curve.  For the mot part, the fas fired roller hearth kiln has replaced the gas fired pusher slab kiln since it is more efficient to operate.