Historical
BS EN 60529:1992+A2:2013
Degrees of protection provided by enclosures (IP Code) (British Standard)
Gives uniformity in methods of describing the protection provided by enclosures and in tests to prove various degrees of protection. Provides an optional extension of the IP code by an additional letter A-D, if the actual protection of persons against access to hazardous parts is higher than that indicated by the first characteristic numeral.
British Standards Institution [bsi]