bulgie 

I think I was the only one at the frameshops where I worked that ever wore a respirator for brazing, and I didn't always myself. I mostly wore it when I had a long stretch of fillet brazing to do, typically a tandem. For fillet, at least if you're trying to do your best, you need to have your face in the plume of rising fumes part of the time. Without the respirator, I sometimes got symptoms of "brass fever" which is from zinc poisoning. Luckily zinc isn't very poisonous and the effects are (as far as I know) only short term. Though there are a few known cases where it was fatal, those are more likely to be foundry or kiln-related, not from brazing. Effects I felt were mild at their worst, just some slight nausea and headache which go away pretty much as soon as you get to fresh air.

Not like cadmium, in the same family as zinc, one level lower on the periodic table (just above mercury), which stays in you long-term and is very toxic. I'm sure you all know that silver filler rods sometimes contain cadmium, so you reeeeally need to know if your silver has it or not, and if it does, just "keeping your head out of the plume" isn't good enough. Brian Baylis might be alive today if he'd used cad-free silver or if he'd used a respirator, but he was famously one of those "just keep your head out of the plume" guys — that might even be an exact quote. He died of a lung issue, maybe unrelated but I'm suspicious.

I am no expert, but I was led to believe that zinc fumes are actually small particulates, that condensed from vaporized zinc after leaving the vicinity of the flame. They aren't vapor, they're solid. So the correct cartridge is, I believe, a HEPA filter for particulates. That's what I used anyway, and I don't remember ever getting any zinc fever symptoms while wearing one — seems to have worked. I also wore a face shield that covers the intake of the cartridges, so hopefully some of the plume was diverted away from the intakes. No filter is perfect, and they don't seal perfectly against your face, so belt-and-suspenders is worthwhile. And you still should keep your head out of the plume as much as you can, if only to extend the life of your cartridges. I don't know how to tell when a Hepa cartridge is used up, so I just changed them once in awhile.

I had a US Divers brand respirator for years, dunno what happened to it. The one I have now is 3M and seems very good. Availability of cartridges might be an issue, unless the mounting interface is standardized? Dunno, but with a 3M mask you know you'll be able to get cartridges for it. Get a pair of Organic Vapor cartridges for it too, if you ever want to do any painting. Keep your organic cartridges sealed up whenever not using them, I hear they absorb stuff out of the air and get partially used up just from sitting unused, if they're in the open air. Heck even with HEPA cartridges, I keep my mask in a snap-lid clear plastic storage bin, if only so it isn't covered in whatever dust and grit settles out of the air in my shop. Ooh, I should move it, store it next to the striker for my torch so it reminds me to wear it while brazing.