Although we regard electrostatic discharge (ESD) as an electrostatic phenomena, since charge is moving, and currents are flowing, it is electro quasi-static. Electrostatic discharge can be initiated by an arc from a person to an object.
The electrostatic discharge event occurs as a result of the breakdown of the air in the gap between the person and the object.
The discharge process is a function of spacing of the gap, the geometry of the gap (e.g., curvature, radius of electrodes), cleanliness of the surface, relative humidity, and speed of approach. So, what is electrical breakdown?