The protection rating of a cooling fan is usually indicated by the IP (Ingress Protection) rating, which represents the fan's ability to resist solid particles and liquids. The IP rating consists of two digits: the first digit indicates the level of protection against solid particles, and the second digit indicates the level of protection against liquids. For example, IP54 means the fan has some protection against dust and can prevent water splashes. The appropriate protection rating should be selected based on the presence of dust and liquids in the operating environment.