1. In an electrode air humidifier for generating steam having a water tank provided with a water inlet and steam outlet, and electrodes within said tank projecting downwardly into water therein, wherein the improvement comprises said electrodes comprising at least three electRodes, each of said electrodes having an overall configuration generally corresponding to an elongated isosceles triangle having its vertex angle pointing downwardly, each electrode being bent on a symmetry line in such a way that the borderline of each flap thus formed, with the surface of the water at any water level, is parallel with the borderline of the corresponding flap of the adjacent electrode, the bending lines being arranged along the edges of a tetrahedron with an equilateral base, said electrodes being slanted away from the vertical decreasing the horizontal distance between electrodes from the bottom towards the top.

3. In an electrode air humidifier for generating steam having a water tank provided with a water inlet and a steam outlet, and electrodes within said tank projecting into water therein, wherein the improvement comprises substantially all the exposed active electrode surfaces of said electrodes being covered with a plastic material in which an electrically conductive pigment is incorporated to make the plastic electrically conductive.

5. An electrode air humidifier for providing a substantially constant rate of steam generation irrespective of variations in the conductivity of supply water, comprising a water tank having a water inlet and a steam outlet, an inlet valve regulating water flow through said water inlet, a plurality of electrodes within said tank projecting downwardly into water therein, current supply lines connected to said electrodes, each of said electrodes having a pair of substantially planar current carrying surfaces whose horizontal dimension progressively increases in an upward direction, said electrodes being positioned relative to each other so that each planar surface on each electrode faces a different planar surface of an adjacent electrode and the horizontal distance between the adjacent current carrying surfaces of adjacent electrodes progressively decreases in an upward direction, and means responsive to current flow in one of said current supply lines to control the operation of the inlet valve to adjust the water level in said tank.