Abstract: A fluid-heating apparatus comprises a ceramic burner head formed with narrow passages which alternate with one another for fuel and a combustion sustaining medium such as air, the slit-like passages opening into a combustion chamber at which combustion of the fuel/air mixture occurs. Downstream of this combustion chamber is a ceramic recuperator likewise formed with slit-like passages, the hot combustion gases traversing some of these recuperator passages while the fluid medium to be heated is passed through others of these passages so that heat exchange is effected through the thin ceramic walls supporting the slit-like passages of the ceramic recuperator.