Ingress Protection (IP)
1st Digit: Solid Particle Protection
0 Not protected
1 Protected against solid objects greater than 50mm
2 Protected against solid objects greater than 12mm
3 Protected against solid objects greater than 2.5mm
4 Protected against solid objects greater than 1.0mm
5 Dust Protected
6 Dust tight
2nd Digit: Liquid Ingress Protection
0 Non protected
1 Protected against dripping water
2 Protected against dripping water when tilted up to 15 degrees
3 Protected against spraying water
4 Protected against splashing water
5 Protected against water jets
6 Protected against powerful water jets
6K Protected against powerful waterjets with increased pressure
7 Protected against the effects of submersion up to 1 m
8 Protected against submersion of 1 m or more
9K Protected against powerful high temperature water jets
IP Rating = NEMA Enclosure
IP20 = 1
IP22 = 2
IP24 = 3R, 3RX
IP53 = 5
IP54 = 12, 12K, 13
IP55 = 3, 3X, 3S, 3SX
IP66 = 4, 4X
IP67 = 6
IP68 = 6P
Both IP and NEMA are broke down in this link: IP code - Wikipedia
Here is a simplified IP Chart from Orion Fans:
The Ingress Protection (IP) rating system is defined by the letters “IP” followed by numbers and characters denoting the protection level. IP ratings replace commonly used terms such as “airtight” and “watertight” with specific levels demonstrating the exact conditions that a product can withstand.
The first character after the IP identifies the level of protection against the ingress of solid foreign objects. The second character identifies the level of protection against moisture/liquids. The latest IP rating to be introduced is IP69K. The character “K” denotes the products’ specific degree of protection for use in road vehicles as per ISO 20653. If the need for protection against permanent water submersion up to 3m is required, IP68 rating is the best-fit for that application.
The first number of the IP69K rating (the “6”) designates that the fan provides the maximum degree of protection against dust particles that might interfere with operation, rendering it dust tight. The second character (the “9”) designates that the fan is protected against high-pressure (up to 1450 PSI), high-temperature (80° C) washdown spraying from less than 4 inches away, at various different angles, for a minimum of 30 seconds at each angle, and a flow rate of 14–16 L/min.