A device for heating air, fluids and materials, in dry or wet environments powered in low voltage current or alternating or direct very safe allowable voltage, by increasing the temperature of any type of surface, whether flat or embossed, solid or open-work. The device includes electrodes coated with a layer of electrically resistant fluid or pasty substance. The assembly of devices is very thin, and is particularly designed for heating premises, swimming pools, pipes exposed to freezing, and container for warm food.