A key change instituted in the 4th edition of the medical EMC standard 60601-1-2, 4th ed, is to test practically all medical devices up to ESD level 4, 15KV air discharge, and 8KV direct discharge. Whereas in the 3rd ed only life support and critical medical devices required this relatively high ESD test voltage. At the 15KV level, it is imperative to use the proper ESD test protocol to obtain accurate test results, and not induce power supply damage by capacitance charge ratcheting.