I was having a discussion with a co-worker yesterday as we were reading an arc flash label on a panel. The label called out "cotton underwear" as part of the PPE. We both know that your underwear has to be cotton or otherwise non-melting, but he asked me an interesting question. "Must you wear underwear"? At first, I thought he was being silly and asking if you needed to wear undershorts. He quickly clarified and said that he was asking about an undershirt (t-shirt). If "cotton underwear" is called out on an arc flash panel label, does that mean you have to put on a cotton t-shirt under your FR shirt as part of your PPE when you get into the panel if you weren't wearing one already?