Try this formula for low lying fog but build a fog chiller by ducting your output into an inexpensive styrofoam cooler in which you have cut a couple holes ( one in each end) and filled with ice and a little bit of salt. It will super cool the fog it's self which will keep it low lying. https://www.froggysfog.com/fluids/low-lying-fog-fluid/freezin-fog-outdoor-graveyard-low-lying-ground-fog-machine-fluid-fog-juice.html. I'm not advertising through the link merely showing what we use in the haunt to create a laser swamp. (A very cool effect for photography I might add)