Ionizers are employed to neutralize the static charge on parts used in the manufacture of a variety of high technology products. ESD considerations are particularly important in disk drive manufacturing because of the extreme sensitivity of their MR heads. Corona ionizers reduce static charges, lowering the voltages on sensitive components such as MR heads, to a small but non-zero voltage. ANSI EOS/ESD S3.1-1991 attempts to characterize this voltage by defining the offset voltage measured with a charged plate monitor. Unfortunately, the voltage on the MR head can be either higher or lower than the offset voltage, depending on its location and the proximity of grounded objects. In this paper, the relationship between the location of the DUT, the offset voltage and the damage threshold are measured and discussed. For objects located more than 15 cm (6″) above the work surface, the accepted 10 V damage threshold for an MR head may underestimate the hazard. When the object is located a few millimeters (∼1/8–1/4″) from the work surface, considerably more than 10 V of offset voltage is required to damage an MR head.