An electrostatic discharge to your product happens really quickly.

As you can see from the diagram, the bulk of the energy has dissipated within 100ns.

That means that any protection circuitry you select has to be able to react quickly to ESD events.

Here are some common test levels that are used when testing electronic devices. The test levels will be defined for your product in your product standard.

A very common test level is 4kV contact, 8kV air, but these values could be higher or lower depending on your standard.

A test lab will start at a low voltage (say 2kV), then if your product passes the lower level, they will increase the voltage and test again. Ideally your product will pass at the specified voltages, but often products exhibit some failure modes at lower levels.