There's loads of things to be watchfull of when welding, I have had zinc poisoning twice due to welding galvanized steel. First time I was in my workshop, silly really, no exhaust, no air fed helmet etc. The second time, I was welding some galvanized palisade fencing outside in the open, there was a reasonable breeze and still I managed to breath some of the fumes. Simptoms are severe flu like aches and pains, severe sweating, headaches, limbs so painful you cannot get out of bed. Fortunately it only lasts 24/48 hours.