“IP” stands for International Protection or, in some circles, Ingress Protection. It’s a standard rating system used to describe how much protection a mechanical casing or “electrical enclosure” can provide. An item’s “IP code” is made up of two numbers. The first one rates its protection against solid objects like dust, with a classification scale between zero, meaning it can’t repel anything, and six, which means none can enter. The second number deals with protection against liquids and uses a scale from zero, meaning none again, to nine, which offers maximum protection.
The IP code was devised so companies could avoid using confusing marketing terms like “waterproof” or dust resistant” entirely. Alas, Apple apparently didn’t get that memo. AirTags have an IP rating of 67. According to Trenton Systems, “The 6 indicates ‘complete protection against dust over extended time’ as well as ‘protection against contact with objects greater than 1mm in diameter, such as a wire or a small tool.’ The 7 indicates the system is ‘protected against short periods of immersion in water while under pressure between 15cm and 1m.'”
Thus, an IP67 designation technically means something is both dust and water “proof,” but only temporarily. AirTags can’t be submerged in more than one meter of liquid — and not for very long time-wise. Apple says 30 minutes or less.
An AirTag’s resistance to “splash, water, and dust” is, according to Apple, also not a permanent condition and will fade over time under normal wear and tear. That means they’ll have to be replaced, especially if you have a penchant for losing things in grimy or moist environments.