A lithium-ion battery is made of multiple lithium-ion cells. Often, lithium-ion batteries are stored and transported near many other lithium-ion batteries. Because of this, it is important to know what will happen to nearby batteries if one cell enters thermal runaway.

This test is known as the fire exposure and projectile test. It determines whether an exploding cell will spread fire on a large scale. Thermal runaway can result in fire and explosion. During the fire exposure test, if a cell explodes and the projectiles from the battery puncture the steel screen it sits on, that indicates that the cell has the capacity to spread fire on a large scale if it overheats.