http://en.wikipedia.org/wiki/IP_CodeThe first digit indicates the level of protection that the enclosure provides against access to hazardous parts (e.g., electrical conductors, moving parts) and the ingress of solid foreign objects.
5 Dust protected Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact
6 Dust tight No ingress of dust; complete protection against contact
The second digit indicates the level of protection that the enclosure provides against harmful ingress of water.[6]
7 Immersion up to 1 m Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion). Test duration: 30 minutes
Immersion at depth of at least 1 m measured at bottom of device, and at least 15 cm measured at top of device