As stated earlier, an ESD occurs on an electronic component can hurt it or cause disastrous failure. Some HDD components are reactive to potentials as low as 10 volts, and Metal Oxide Semiconductors are most probably damaged by potentials as low as 25 volts. While walking on the carpet in a low-humidity room can generate 35,000 volts, and a human generally can’t get a discharge of less than 3,000 volts.

MOS technology uses the capability of an electrostatic field to cause things to happen on the each side of an insulator, making for a smaller transistor and considerably low power usage in comparison with the bigger traditional transistor technologies. But due to the small size, the level of metal oxide glass is very susceptible to get hurt by higher than normal voltage layers, causing it to open and allowing the current to flow.

Of course, disastrous damage can easily be noticed. The part doesn’t work. Degradation of a component is hard to notice. If one is able to use a high-powered mic, then the damage can be noticed: joined conductors, vaporized sections, rough edges, etc. Your parts might work well till the time it starts to get heated; or it will develop irregular failures or stop working in a particular mode. The useful life of the part will be reduced significantly, for sure.