These ovens utilise diesel (HSD / LDO) as a fuel. The fuel is fired with the help of imported burner inside the heat exchanger made of stainless steel. The blowers mounted in the heater box circulate the oven air over the heat exchanger thus oven air is heated indirectly. Flue gases after burning the fuel are exhausted to the atmosphere through chimney. The burner is fully automatic and controlled by temperature controller. The burning is totally clean without formation of any soot. Heater box is generally top mounted to save floor space. However it can be mounted on any side of the oven, Initial cost of these ovens is higher but running cost is less than 60 % as compaired to electrically heated ovens.