Every AED has an "IP Code". The IP Code is the "International Protection Rating" or "Ingress Protection Rating. The code is expressed as IPXX with "X" being numbers. For example, you may find an AED on the AEDexpert website that has an "IP" Rating of 55(This is one of the highest IP ratings).
The first numerical digit indicates the level of protection against contamination from solid particles such as dust, dirt or other matter. The second numerical digit indicates the level of protection from water. The higher the value of each number the higher the resistance to these contaminants.
You can refer to the scale below when you compare different defibrillator models:
No protection against contamination from dust or dirt
Protection from large objects, the size of a fist, but no protection against deliberate contact with a large object
Protection from objecs the size of a finger or similar objects
Protection from objects the size of tools, thick wires, etc
Protection from most objects the size of wires, screws, etc
Dust-proof - Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment
Dust-tight; complete protection against contact
The second numerical digit indicates the level of protection from water contamination:
Dripping water when tilted up to 15 degrees
Powerful water jets
Protected against submersion Up to 1 meter and for 30 minutes