How is spark formed, and why might a spark start an explosion?

When the applied electric field exceeds the dielectric breakdown strength of the intervening medium, a spark is generated. In a mechanism known as dielectric breakdown, the exponentially increasing electrons and ions allow regions of the air in the gap to become electrically conductive.

An electrostatic spark causes the blast. The sudden rise in temperature that occurs as the mixture ignites causes a massive increase in gas pressure. The ensuing increase in pressure could collapse the chamber with a noisy explosion if the burning vapour were to be trapped.

Explanation:

2%? i tried finding the exact sorry if it's not 100% correct ; -;