54178de2_tings_and_IP_Equivalency_Chart__NEMA_Definition
[NEMA Rating] 4 [IP Equivalent] IP 56 [IP Definition] 5 = Protected against dust - Limited to ingress (no harmful deposit) [4] 6 = Protected against strong jets of water from all directions - Limited to ingress permitted. [NEMA Definition] 
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment; to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water, and corrosion; and that will be undamaged by the external formation of ice on the enclosure
Rugged Technologies - NEMA Ratings and IP Equivalency Chart
NEMA Definition