Step one: get a fume hood - no way to safely do these reactions without one. I didnt have one when I first got started. A whiff of nitrogen dioxide here, a breath of chlorine gas there, SO2 fumes are the worst - for me. I didn't think it was that bad. My legs would suddenly develope cramps so bad while seated that I had to stand and walk them off before I could sit back down. I believe that this was due to breathing NO2 fumes because I didn't have a fume hood. Today, if I get any SO2 gas in my lungs at all, my lungs swell up and it interferes with my breathing for an hour or so. I believe that I've developed a sensitivity, due to breathing the SO2 repeatedly, when I first started refining, as I added SMB to precipitate gold - with no fume hood. Some will say, "I'll just do the reactions outdoors and make sure the wind is blowing the fumes away from me." Here's the problem with that line of thought: no matter how well you can hold your breath, and even if you approach the reaction outdoors from the upwind direction, the fumes will still wrap around your body from the eddy currents of airflow and draw the toxic fumes towards you. The fumes will get in your face, on your skin, in your eyes, hair, and clothing. Even if you turn and walk ten paces away, when you finally draw a breath (after trying to hold it while adding the reagents), the fumes will still be there and get drawn into your lungs. Slow chronic low dose exposure, as described above, will take its toll on your health. There is no way to safely do these reactions without a fume hood. This has been my experience.