If you were welding Galvanized steel sheet, breathing the zinc oxide produced can cause "metal fume fever". In addition to Zinc it can be caused by cadmium, chromium, copper, nickel and lead.
The symptoms can include dizziness, nausea, vomiting, cold sweats, shakes, chills, disorientation, headaches, inflamed lungs, pneumonia and/or a feeling you are "too sick to die"