You can build a fog chiller. Easiest way is to take some sort of pvc or similar pipe and run it fom the fog machine, through a large cooler full of ice and out the cooler. The ice chills the fog, and keeps it creeping along the ground. Heat rises and when the fog comes out of the machine it usually rises instead of staying on the ground unless you chill it. Hope that helps.
Might run the risk of messing something up if you do that.. I think that the machine heats the fog liquid up to make the fog, so if you put ice in the machine it would probably jus take longer to heat up and make fog. The fog needs to be cooled after it come out of the machine. It is the same principle as natural fog, the cold air keeps the vapor low, basically.
Here's a really cool way to do it:<a href=\"http://www.gotfog.com/fog_machine_chiller.html\" target=\"_blank\">http://www.gotfog.com/fog_machine_chiller.html</a>
I'd sell you a used one for 450.00 plus shipping. Used one time.Antari ICE Low Lying Fog Machine<a href=\"http://www.hauntedfog.com/Pop%20Ups/Antari/antari_ice_low_lying_fog_machine.htm\" target=\"_blank\">http://www.hauntedfog.com/Pop%20Ups/Antari...fog_machine.htm</a>