then term "nema" is from the national electrical manufacturers association - a US manufacturere organization. nema standards describe each type of enclosure in general and functional terms, and specifically omits reference to construction details.
NEMA 7 is defined as a hazardous location type of enclosure.
NEMA 7 - enclosures are for use indoors in locations classified as Class 1, Groups A,B,C, or D, as defined in the NEC. Nema standard 1-10-1979.
this is from the Weigmann enclosure catalog dated 1996. other enclosure brands should also have this listing in their catalogs if you have one handy.
hope this helps.
