Today Ernie came over and helped me set up my '96 Millermatic 250 and then showed me and a few buddies the basics of MIG welding. I'm running .035" E70S-6 and C25 gas, and this machine welds sweetly from 16 gauge nice smooth little bead up to where Ernie turned it all the way up and kicked it into spray mode on1/2" plate - wow. Can't do that very long on that light duty M-25 gun, though.
I found that there is a little welding smoke, not too bad welding inside the shop about 3 feet from a large open garage door. But in cold weather I'm still going to use an exhaust fan. I scrounged an old fan once with a 3/4hp 3450 rpm motor on it, has 2 input ports 3" round, and one rectangular duct output 3½x4". I made up a transition from rectangular duct to 6" round (actually about 3/8" less circumference than 6" round would be, my flex ducting wouldn't go onto 6" steel tube) and tacked it together with 6010 at low amps. Today after Ernie left for the first time since 1970 I was able to weld up light-gauge steel - I welded up the transition, now I can use my cobbled up fan with a really beat up shorty piece of rasty-butt 6" exhaust duct and a 3" super-light flex aluminum dryer duct for the intake duct, and move my welding operation inside for the winter.
I'm happy. I do like my Millermatic. I splurged and dropped $200 on the spoolgun module (built in on the 250X and 251s) and now I can run a spoolgun and weld aluminum too, the other thing I haven't been able to do yet.