Equipment intended to operate in challenging environments may need provisions for environmental resistance and tolerance. To convey confidence that a product meets specific requirements, these provisions may be tested and rated in accordance with standards. Some of the most common sets of standards cover ingress protection - the resistance of equipment or enclosures to resist exposure to solid objects or liguids. Two sets are commoly used - IEC 60529 IP ratings and NEMA 250 ratings. The capabilities of each rating level is shown in these charts with approximate equivalence, where applicable. Manufacturers my provide other combinations of IP and NEMA ratings by testing for specific requirements of each. Not all possible IP combinations are meaningful or available. For a more detailed comparison of the IEC and NEMA requirement, download this document from NEMA (registration required).
If the second IP digit is Zero (0), then the enclosure offers no protection against water.