IP (International Protection) is an internationally accepted designation that characterizes the specific product's degree of protection against foreign bodies entering the enclosure - dust, moisture, and others.
  1. The first digit indicates protection against solid objects and dust entering the enclosure.
  2. The second digit indicates protection against water entering the enclosure.


The first digit can range from 0 to 6, and its meaning is as follows:
0 - no protection (none);
1 - protected against solid bodies larger than 50 mm;
2 - protected against solid bodies larger than 12 mm;
3 - protected against solid bodies larger than 2.5 mm;
4 - protected against solid bodies larger than 1.0 mm;
5 - protected against solid bodies smaller than 1.0 mm;
6 - dust-tight.
The second digit can range from 1 to 8, and its meaning is as follows:
1 - protected against vertically falling water drops;
2 - protected against water drops at a 75-degree angle;
3 - protected against rain;
4 - protected against splashes from below;
5 - protected against water jets;
6 - protected against waves;
7 - protected against temporary immersion in water;
8 - protected against prolonged immersion in water.
For example, IP 44 means that the device can be used not only indoors but also outdoors, not in very dusty environments and not under strong flowing water or direct rain.


More information about IP marking can be found at: Wikipedia.