Why not have a fan that is at the end of a tube that is inserted so many inches into the chamber. Also, have the tube at the top of the chamber so that any condensation that does occur is forced down the pipe. Have this fan blowing into the fog chamber. Also, since you dont really want it to be exhausting all your fog, use a cellphone charger, which are around 5-6v as opposed to a 12v. Makes the fan much slower. Just a thought, see if it works if ya run out of ideas.