Our different smoke fluids are made for different purposes: They vary in the denseness of the smoke and its durability. Depending on the desired effect, these characteristics are important.
The fog build by fluid B vanishes very quickly. That´s why it is perfectly suited for short smoke effects, for example. In a same sized room, smoke created by fluid C needs twice as long to vanish totally. The smoke fluid E provides a very dense smoke, which needs ten times as long (as B) to disappear.