Recently purchased a couple of Miller LPR-100 Half Mask Respirators (with the low profile to "fit" under welding helmets). Feedback: in theory these "work", but in practice not so much. The Miller LPRs are the best fitting of all half mask respirators I've tried, but they do create an awful lot of condensation on the inside of my welding helmets and we all know visibility through these sensing helmets is critical-- condensation seems to be almost unavoidable, but these respirators are life savers and help to filter particles, aerosols, other welding fumes products.

You still can't beat having a fume extraction system. I opted for the $200 variant using a fan and a long tube positioned overhead, but frankly don't use it much because like most of us stationary welding at a station isn't reality -- I'm normally welding in all sorts of locations and the fume extractor isn't practical so the fall back is half face respirators.

If you weld a lot (remember the old saying "there aren't many old welders" and its medical implications) I'd recommend these Miller LPRs -- seem to be best of breed with (however) some lingering issues, notably the condensation build up problem.