An arc flash incident can ignite clothing when performing electrical work. Clothing can ignite in welding and hot work because of heat, sparks, or flame.
Fabric made of natural materials will burn, but these materials will just turn to ash. Polyester, nylon and acrylic will melt if burned and can increase the severity of injury.
I like to wear colored t-shirts commonly found in stacks at various retailers. These shirts are usually priced around $5 each. Many of my shirts were wearing out and were sent to the rag bin. I went to Wal-Mart and purchased a half-dozen new ones. After a couple of weeks wear, I noticed pilling on some of the shirts and checked the tag. Many of these shirts were a 50% cotton/polyester blend. I assumed all these shirts were 100% cotton from past purchases. Because I do both welding and electrical work, these shirt will not do. I will donate them to charity.
Always check the tag.