A fog chiller is a box you run your fog through to cool it before releasing it. Chilled fog stays low to the ground and creeps. You can make them out of an old cooler. You take flexible dryer tubing, snake it through the inside of the cooler like intestines, have the ends of the tubing attached to holes you have drilled on either side of the cooler at the base, fill it with ice and position it at the end of your fogger so the fog runs through the tubing and gets chilled.