The two digits in an IP rating answer two different questions: how well the enclosure keeps out solids, and how well it keeps out water.
| Rating | Solids | Water |
|---|---|---|
| IP65 | Dust tight | Low-pressure jets |
| IP66 | Dust tight | Powerful jets |
| IP67 | Dust tight | Immersion to 1 m for 30 minutes |
IP67 isn’t automatically better than IP66. An enclosure can survive immersion and still fail under a pressure washer.