Is it ensure, insure, or assure?
(ESD) One kind of test that hardware usually has to pass to prove it is suitable for sale and use. The hardware must still work after is has been subjected to some level of electrostatic discharge. Some organisations have their own ESD requirements which hardware must meet before it will be considered for purchase.
Different countries have different legal regulations about levels of ESD.
See also Radio Frequency Interference, Electromagnetic Compatibility.