Abstract: A combustion box comprising an inner casing with a tubular configuration and hollow therein, which is housed in a volumetric housing, the casing running through the inside of the housing, and each one of the ends of the inner casing is in contact with the inner contour of the volumetric housing, such that said ends pass through the inner contour of the volumetric housing, there being an inner intermediate space between the inner contour of the housing and the inner casing, and said intermediate space containing a flammable solid material.