IP Rating sometimes is referred to as Ingress Protection Rating but is more commonly known as International Protection Rating.  An international committee the International Electrotechnical Commission defined this standard originally in 1998.  The US ANSI (American National Standards Institute) and NEMA (National Electrical Manufacturer’s Association) are members of IEC and contributed to its development.

This standard is typically applied to commercial products and their ability to keep the environment from interfering with the operation of a product.  Ratings are defined by the letters IP followed by two digits and an optional letter. As defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures. The standard aims to provide users more detailed information than vague marketing terms such as waterproof.

The National Electrical Manufacturers Association (NEMA) in the United States also publishes protection ratings for enclosures similar to the IP rating system published by the International Electrotechnical Commission (IEC).  NEMA however also dictates other product features not addressed by IP codes, such as corrosion resistance, gasket aging, and construction practices.  For this reason while it is possible to map IP Codes to NEMA ratings that satisfy or exceed the IP Code criteria, it is not possible to map NEMA ratings to IP codes, as the IP Code does not mandate the additional requirements.

North American enclosure rating systems are defined in NEMA 250, UL 50 (Underwriters Laboratories), UL 508, and CSA C22.2 No. 94 (Canadian Standards Association).
  
IPX Standard Code Meanings 
    • IPX-0 No special protection 
    • IPX-1 Protected against falling water Equivalent to 3-5mm rainfall per minute for a duration of 10 minutes.
    • IPX-2 Protected against falling water when tilted up to 15 degrees - Same as IPX-1 but unit is tested in 4 fixed positions - tilted 15 degrees in each 
      direction from normal operating position. 
    • IPX-3 Protected against spraying water - Water spraying up to 60 degrees from vertical at 10 liters/min at a pressure of 80-100kN/m2 for 5 min. 
    • IPX-4 Protected against splashing water - Same as IPX-3 but water is sprayed at all angles. 
    • IPX-5 Protected against water jets - Water projected at all angles through a 6.3mm nozzle flow rate of 12.5 liters/min at a pressure of 30kN/m2
       for 3 minutes from a distance of 3 meters. 
    • IPX-6 Protected against heavy seas - Water projected at all angles through a 12.5mm nozzle at a flow rate of 100 liters/min at a 100kN/m2
       pressure for 3 minutes from a distance of 3 meters. 
    • IPX-7 Protected against water immersion - Immersion for 30 minutes at a depth of 1 meter. 
    • IPX-8 Protected against water submersion - Equipment suitable for continual submersion in water under conditions  as specified by manufacturer.