There are 3 types of ESD: Sparks – A spark is triggered when the electric field strength exceeds approximately 4-30kV/cm. This may cause a very rapid increase of free electrons and ions in the air, temporarily causing the air to abruptly become an electrical conductor. Corona discharge – A corona discharge occurs between a highly curved electrode and an electrode of low curvature. Brush discharge – A brush discharge occurs between an electrode with a curvature between 5-50mm and a voltage of about 500kV/m. The resulting discharge paths have the shape of a brush.