The solution to this is to build a fog chiller. The fog chiller cools the hot fog from the machine, causing it to stay low and billow along the ground.
This is a small fog chiller, which works well and is cheap. It takes an hour or two to build.
Step 1: Design and Theory
The principles behind a fog chiller are the ideal gas laws. The warmer air is, the less dense it is, and therefore is pushed upwards by sinking cold air. Simply put, warm air rises, cool air sinks.
Fog machines work by pumping fog liquid onto a very hot "heat exchanger", which flash-vaporizes the liquid. This expansion pushes it out of the nozzle. The fog exiting the machine is very hot, and will rise up.
This device cools the air in which the fog is suspended, therefore causing it to sink to the ground.
I designed this chiller myself, and I think the design is unique.
Fog enters the device at the top. At the top, there is a large expansion chamber, so that the fog can properly mix with the air.
Below this expansion area, there is ice. This cools the fog. Once the fog is cool, it will sink down below the ice into another chamber.
On one end of this chamber, there is a fan to blow the fog. On the other end, there is a hole for the fog to exit. This further mixes the fog with the air, and blows it out.
The theory is that the fog will expand in the first chamber, as well as cool. Once the hot fog has cooled enough to sink below normal air, it drops below the ice and is blown out.
If the amount of incoming fog is too fast for the cooling, then the fog will not cool as much, but will still be forced through the layer of ice, most likely resulting in enough cooling to retain the effect.
The whole device is fairly small, only about twice the size of a fog machine, and can be built with easily obtainable materials for not much money.