Implosion is a process in which objects are destroyed by collapsing on themselves. The opposite of explosion, implosion concentrates matter and energy. An example of implosion is a submarine being crushed from the outside by the hydrostatic pressure of the surrounding water.
When product or air is withdrawn from a tightly sealed, unvented storage tank, a vacuum is created within the tank. As the amount of vacuum increases, atmospheric pressure on the outside of the tank is no longer balanced by pressure inside the tank, causing the tank walls to collapse inward. This event is referred to as an implosion.