Years ago I worked for an aerospace sub-contractor and we welded titanium there. The parts were small so we had a tank we put the parts in and had a tig rig set with rubber gloves (so we could handle & weld the parts). We worked under the scrutiny of the FAA and maybe this was over kill, but the chamber was air-tight and the first thing we did (after loading the parts to be joined) was to purge the tank with Nitrogen.....The chamber was 4' X 2' and 3' deep and made of plex-glass. An outlet (check valve) was set up near the top of the tank to vent out the Oxygen (major contaminant for titanium welding) and 2 hoses (at the bottom of the chamber) were set up-one had N2 and the other had pure argon. We also had an Oxygen meter (the probe was near the top, away from the check valve). N2 was used to purge the chamber of Oxygen (since N2 is way cheaper than argon) and once the O2 read less than 2 tenths of 1% oxygen was present, then you would close the N2 supply and turn on the argon. They had calculated what time an area would take at say 25 cfh to fill the chamber with those dimentions I have given.....I think it was 15 minutes, anyway it's not too difficult to figure out, but you always had to keep an eye on the O2 meter.
Like I said, this chamber was monitered by the FAA and everything was radiographed and occasioally there would still be problems with parts welded in the chamber.
We used 2% thoriated tungsten and the rig had a gas lense with a flow rate of 25-35 cfh of argon. We taped a# 10 lense at a location where we could weld and see the work well.
Hope this helps. Weld on!