All foggers use fog juice (fluid) even the ones that have a place for ice, you put the ice in there to cool the fog down so that it stays low to the ground.
Wind for the most part. The outside enviroment makes it much harder to keep fog at ground level from my personal experience so more extreme cooling I found was needed.Texmaster, why do you say it would only work well inside? I have always (the past 3 years) shot my fog machine through a tube like that filled with either dry ice, or just regular ice. It has always worked well for me. This is the first year that I will make one out of a storage bin and a dryer lint hose. Haven't built it yet so I really don't know if it will be any different.