I'd like lightweight respirator that doesn't have to be chucked at the end of the day. Do they exist?! Everything I've come across seems to be disposable.
not actually rated for welding use but they keep my nose clean and work ok with my glasses. The rubber mask part actually seals well against the face unlike the cheap disposables
It depends if you are a business, if you are then I believe health and safety will mean you are restricted to one month's use
For me as an individual I keep re-using it until them until I either damage them (flying debris from grinding) or clog them up so it gets more difficult to breathe through (using a core drill in a restricted space a single hole through a 9inch wall did for one)
in the garage with perhaps up to 3-4 hours cutting/grinding/wire brushing/welding per weekend I would probably re-use one mask for 4 months or more but I do put them away in the quick seal bag after use. From your brief description I would expect you to get way more than this. The rubber surround makes them quite robust. I sometimes have quite a dirty face around the mask when I take it off and a nice clean patch underneath
Difficult to be more accurate but they seem pretty good at keeping all the crud out and for the money it has to be worth getting one to see how they fit you
There are loads of different versions so have a look around as they quite often can be bought quite cheaply if you are not too specific