Ionizer and discharge electrode assembly to be assembled therein

bbAn ionizer of a corona discharge type is configured to increase the yield of ions while minimizing contamination of a discharge electrode by foreign matters. In the ionizer, a gas path unit supplied with clean gas has internal clean gas paths in an electrode assembly, and clean gas is released through each internal clean gas path to make a clean gas flow enclosing a front end portion of a discharge electrode. The electrode assembly has a guard ring encircling the discharge electrode, and the guard ring has external air inlet openings permitting free passage of atmospheric air. The clean gas flow enclosing the tip of the discharge electrode inhales atmospheric air through external air inlet openings of the guard ring and changes to ionized air.