I have heard about potential health hazards when soldering. Such as the rosin fumes causing asthma or the lead oxide (or something like that) causing lead poisoning. Are these concerns valid? Should I take precautions such as wearing a breathing mask, or would a simple fan blowing away the smoke suffice? I do not solder often, but when I do, I solder in 2 to 3 hour segments a couple times a week in a large room. Any advice would be appreciated.