Per table 130.7(C)(10) a hard hat is required for HRC 1 to 4.

I have read that hard hats that meet ANSI Z-89.1 (which most if not all industrial facilities use) do not provide any protection from an arc flash, and in fact could actually melt into the person's head or even ignite if exposed to an arc flash. (Source: "The Electrical Safety Program Book" pg 71, co-author is Ray A. Jones who is an NFPA 70E committee member)

What is to be done regarding wearing a hard hat?

The same book suggests wearing a switchman's hood over the hard hat when within the arc-flash protection boundary.

Are we to wear a hood when in a HRC 1? Impossible!