Daniele De Luca explains how to add 'pre-roll' to your smoke simulations so they'll come into full action straight away.
In this small tutorial we will create a smoke simulation with pre-roll.
The pre-roll that is a cache on negative frames in order to run the simulation for a specified number of frames prior to the beginning of the actual animation.
Because of that, the smoke/fire will be already initiated when the animation starts.
Blender seems to have this feature perfectly working into the cloth simulation tools but in the smoke domain lacks a menu for this simple function.