Biomedical Engineer Don Witters (left) and Don Marlowe discuss electromagnetic interference (EMI) with powered wheelchair control systems. Because of their expertise in dealing with medical device EMI, FDA suspected EMI was involved in reports of powered wheelchair users experiencing uncontrolled and unintended movement near mobile radio transmitters. The OST Electrophysics Branch laboratory evaluated several of these devices and developed a procedure to test wheelchairs and motorized scooters for susceptibility to radio transmissions and other sources of EMI. The FDA protocol became the basis for the EMI immunity tests of the ANSI/RESNA powered wheelchair standard and the ISO draft standard.