The specification describes a tunnel kiln adapted to be heated with gaseous etc. liquid fuel, in the case of which the fuel is supplied to at least one horizontally arranged pair of burners, which are directed from the lateral limits of the tunnel kiln and in its lower part towards each other and burn in separating channels underneath the stacking surface of kiln in vehicles adapted to pass through the tunnel kiln. The burners directed towards each other of some pairs of burners are offset along the direction of travel of the firing vehicle in the tunnel kiln channel by a distance which is equal to at least the thickness of the partition between the firing channels and is at the most equal to the clearance firing channel width.