Why would you heat it so hot as to let it fume?
I've been using FeCl for years, heated to about 50C / 130F in a microwave oven. I did not care to get a heated tank, or put in air bubbles.
Etches anything in about 8 minutes (maybe 9 if there is too much copper to take). I tie a piece of wire in a hole in a corner of the PCB and agitate constantly. 8 minutes is not too much of my time. Perfect results.
I know with very heated FeCl you can do it in 4-5 minutes, but is it really worthwhile?