The ion chemistry of the ions derived from wire spring relays has been found to be dominated by the presence of diethylphthalate (DEP), C12H14O4, derived from the cellulose acetate around the relay coil. Under our experimental conditions, using 0.5‐A resistive break arcs in air and in pure gases at a pressure of about 1 Torr, the positive ion current extracted from the arc was found to consist almost exclusively of this compound and its derivatives; with both air and contact metal ions present as minority species if at all. This indicates that the characteristics of DEP are such that charge‐exchange and clustering mechanisms operate to selectively transfer the charge to the organic material. Minute amounts (< 10−5Torr) of DEP will accomplish this transformation in less than 1 msec. DEP has been found to activate relay contacts when present in air in part per million quantities. There are indications that the reactions of diethylphthalate are not unique and that other organic materials will similarly affect the ion species derived from the relay arc.