This is a subject that is under review for the next edition of the NEC.
As it now stands, only a registered 'professional engineer' is deemed as qualified to make the determination of where the 'classified' areas are.
There is a proposal the change this to "qualified person." This is NOT a loophole- nor should it be considered a meand for just anyone to wave a wand and say "I'm qualified." Rather, the proposal asserts that having a PE license does not infer any expertise in this area at all, and that there are many other professions out there that do have expertise here.
As a general rule, it is NEVER the responsibility of the electrician to make this decision. Don't let anyone stick you with it; there is too much at risk.
Nor is someone's assertion that "they do it all the time" enough. If they won't sign, their opinion is just eyewash. At the very least, rely upon your local inspector; he ought to know where to get the information.
