Like PegLeg I've found out about flames and sparks around polyester. I know from personal experience that spot welders can blow a hole through a cotton flannel shirt and give you second degree burns, but at least it isn't melted to your skin and continuing to burn you. I've always worn cotton or cotton/poly shirts, usually 50-60% cotton, and cotton underwear, but I don't live in a place where people commonly get swamp ass. If I ever had to move down south for any reason I think I'd wear everything moisture wicking I could get from my underwear to my shirts and pants. I consider you guys in the south to be the experts. I sometimes break a sweat but manage to get by with my plain cotton clothes that don't melt.