Part Names

An Office Open XML part name shall contain only ASCII characters, in non-escaped or escaped form. The following ASCII characters are permitted in non-escaped form: "!", "$", "%", "&", "'", "(", ")", "*", "+", ",", "-", ".", the decimal digits "0"–"9", ":", ";", "=", "@", the Latin alphabetic characters "A"–"Z" and "a"–"z", "_", and "~". All other ASCII characters are permitted only when escaped as an encoded triplet of the form "%HH", where H is a hexadecimal digit.]