EEVblog #678 – What is a PCB Spark Gap?
In this tutorial Dave explains what a PCB spark gap is and how it can be a useful zero cost addition to your PCB layout to help prevent ESD damage.
He shows how to easily design them into your board and calculate the approximate voltage rating.
And of course has some fun applying 5kV to some gaps to show how them at work.
For more detail: EEVblog #678 – What is a PCB Spark Gap?