If you do not want esters to vaporize, they should not be applied on hot, windless days. I learned that many years ago applying a mix of ester and RoundUp to wipe out an area next to a row of trees. 90 degrees that day, no wind, and humid. I should have been in the pool or at the beach instead of spraying. The only reason it is safe for me to apply esters is a constant 5-15 MPH wind. However, spray nozzles that do not apply a directed spray are no good. AI tips means you can apply in that type of wind without the spray mist going off target. Metsulfuron flying miles down wind is just as bad, if not worse than 2,4-D. I usually use metsulfuron on grazed areas because of how it controls broadleaves for a long time. 2.4-D, triclopyr, or even dicamba do not really last.
My truck mounted boom is normally used on flat grass areas that are too big to walk. It is fitted with AI nozzles spaced at 20". I am normally 16" above the ground. Output is controlled via a Teejet rate controller and GPS guidance system. No foam drops on the ground or blue dye. I rather not call attention to a treatment. On rough areas, I spot treat on foot, but even that hand piece has an air inducted tip.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738