This test is known as the fire exposure and projectile test. It determines whether an exploding battery will spread fire on a large scale. This has become important to watch out for when batteries are transported. Consider: Why do you think this test is relevant to transporting batteries? Lithium-ion batteries are small and powerful. Behind this power is a volatile chemistry. When an object near a battery heats up, the battery itself can heat up, too. Thermal runaway is a rapid, uncontrolled temperature increase that leads to further temperature increases. Thermal runaway can result in fire and explosion. During the fire exposure test, if a battery explodes and the projectiles from the battery puncture the steel screen it sits on, that indicates that the battery has the capacity to spread fire on a large scale if it overheats. UL Safety Engineers push batteries to the extreme with a variety of tests designed to anticipate how a battery might be used or misused, evaluate potential dangers, analyze the effects of a fault or failure and engineer safer solutions. (Don't even consider trying this! Tests are done by trained professionals. Products are tested in a controlled environment with intent to fail.)