The Annexes of the NEC are often overlooked, yet can make a huge
difference in the cost and delivery of projects that involve
expansion, renovation, or upgrades. Reviewing your bill of
materials against Annex A can prevent the cost of ripping out
installed equipment and materials, then replacing with other
equipment and materials your insurer will accept.  For example,
suppose your company has decided to bring database work in-house
for security reasons. So, you're going to have a UPS and some
high-end work stations. The electrical equipment isn't an issue,
because the distributor you deal with carries only listed
components. But what about those office furnishings?  You can
look that up in Annex A and then specify they must conform to
UL1286. That UPS, by the way, should conform to UL 1778. The
surge protectors you're going to install should conform to IEEE
C62. If you were doing a project that involved combustibles,
you'd look in Annex A for the relevant ISA standards.  Annex E
is another NEC resource that