A body of a specially prepared, porous vitreous carbon which does not crack or substantially change in electrical resistance with time when heated to elevated temperatures in air and which is used in a method or apparatus to heat a fluid stream flowing in the pores of the body as a result of natural convection or pumping of the fluid is described. The body is composed of electrically conductive rigid, interconnected and multidirectional continuous strands of vitreous carbon forming a rigid porous, three dimensional skeletal structure. The body as an electrical resistance element has current conductive paths between at least two regions; is shaped to provide particular cross-sections along the conductive paths; and has electrical connector means attached at the regions of the body so that current can be distributed through the body. The electrical resistance element is particularly useful as a heating element for air flowing through the pores in electrically powered room space heaters, hair dryers, hand dryers and the like and can also function as a self-cooling resistor. In a like manner, electromagnetic energy is used to heat a body of the porous vitreous carbon so as to heat a fluid stream flowing through the pores.