We use an older Royal FilterMist on our ST20 lathe.
It's very good at removing the coolant mist from the machine, especially when using the 3 jaw. In most cases, it is completely clear inside by the time the spindle stops and you open the door.
The downside to it................it's NOISY.........very noisy! It also does resonant throughout the machine and can be felt just placing your hand anywhere on the sheet metal, or even holding the door for that matter.
The second, and perhaps biggest problem with it is smoke.........it does NOT filter out smoke. As much as we clean off all the oils from our carbon, stainless, and alloy steels before machining in the lathe, there is still a considerable amount of smoke the filtermist does not prevent.
It is my understanding that the newer models do have an "after filter" that is just for that purpose though, so it is something I would strongly consider should you be working with anything other than aluminums, and plastics.
The whole kit, filtermist, electrical kit with starter, and after filter will set you back about $3,500.00 so choose wisely!
Later,
Russ