Just a heads up, I spent a lot of time finding the best source for CO2 in the Lexington area. By far the best deal and the most pleasant folks to deal with is Holston Gasses on Blue Sky Parkway off Athens-Boonsboro Rd.
I paid $21+tax to swap out a 20# cylinder and my cylinder's hydrostatic test was out of date.
Dobie Swift "In every walk with nature one receives far more than he seeks" ~ John Muir
One thing thought, don't waist your time if you got anything smaller than a 5-lb tank, they can't fill it (as in paintball tanks). if you have a small tank,(as in paintball tank) go to Dick's sporting Good's, 4.99 for 20 oz. fill up.