Is a welders hat/cap actually PPE? Is it written somewhere?

For further explanation,

I am the welder/fabricator/fixture maker. I work in what is essentially an office building. I have a small shop in the middle of cubicle workers and micro/analytic lab personnel. It is a very corporate environment. It is a Worldwide Corporation.

Corporate has now taken to implementing and enforcing a dress code. Hats are not allowed. I have made my case that my Kromer cap is in fact PPE and not a fashion statement.

As of right now that message is not being received well.

Is it written anywhere that our hats/skull caps are in fact PPE? It would help my case that it is PPE. And I really don't like spatter burned into my scalp.

I am not even sure where to begin looking for this info. Anywhere else I've ever worked knew the deal so no further conversation was required.

TIA