The Laser Level IP rating is an international standard for rating how dust and water resistant an enclosure or a device is. Laser Level IP rating.
The IP is followed by two numbers the first is a rating for dust and the second for water and the higher the number the more it can handle with 1 being the lowest and 8 (6 for dust) being the highest, note that only a water rating of 8 means it’s safe to submerge the laser for any period of time, very few laser fall into this category the RedBack PL650 Pipe laser is an example.
IP stands for Ingress Protection; For dust (the first Digit) 0 is not protection, 3 is protected for objects greater than 2.5mm, 4 is 1.mm, 5 is “dust protected” but may let some in and 6 is “Dust Tight”. Most outdoor lasers are rated between 4 and 6. If there is no first number just an “X” then it’s not rated for dust.
The second digit is water and here are some of the definitions; 0 is no protection, 2 protection from dripping water, 4 protection form sprayed water from all directions, 5 water jets (higher pressure), 6 streaming water, 7 short term immersion and 8 full submersion. Remember though if any laser gets wet its best to dry it off before storing away as this can cause damage to even quite high IP rated equipment.