Luminaires that may not be used in all environmental conditions are classified into so-called IP protection ratings (IP = International Protection), in German Internationale Schutzarten, and are marked as follows. The designation follows the following scheme:
IP XX
The letters IP stand for protection rating and the XX are replaced as follows:

1st digit: Protection against contact / protection against foreign bodies
2nd digit: Water protection

Code digits for protection against contact
IP0X Neither protection against contact nor protection against foreign bodies
IP1X Back-of-hand protection - Protection against foreign bodies with diameter >50mm.
IP 2X Keeping fingers away - Protection against foreign bodies >12mm diameter
IP 3X Protection against touching with tools (test probe: 12mm diameter, 100mm long) Protection against foreign bodies with diameter >2,5mm
IP 4X Keeping tools and similar objects away - Protection against foreign bodies >1mm diameter
IP 5X Complete protection against contact - Protection against harmful dust deposits inside
IP 6X Complete protection against contact - Protection against dust ingress (dust-tight)

Code digits for water protection
IP X0 Not protected against ingress of water
IP X1 Protected against vertically falling dripping water
IP X2 Protected against dripping water falling at an angle - (15° from vertical)
IP X3 Protected against spray water - (up to 60° from vertical)
IP X4 Protected against spray water
IP X5 Protected against water jets - (from all directions)
IP X6 Protected against ingress of water during temporary flooding
IP X7 Protected against ingress of water during immersion
IP X8 Protected against ingress of water during immersion for an indefinite period