A method and device for measuring ion concentration in a defined space including disposing at least one conductive surface in a defined space, generating a flow of ions from an ion generator having an anode and a cathode into the defined space, measuring one of voltage across or direct current (DC) through a resistor connected between the cathode and the at least one conductive surface, and determining ion concentration in the defined space based upon a proportionality of ion concentration to the measured voltage or current.