IP (or “Ingress Protection”) ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies (tools, dirt etc.) and moisture.
First Digit = Indicates Dust resistance, or intrusion protection i.e. the size of partial that can enter the enclosure – “1” – Being the lowest , having little or no protection and “7” being the highest, totally dust proof.
Second Digit = water or moisture protection i.e. “1” Being the lowest , having little or no protection and “9” being the highest, protected against prolonged effects of immersion under pressure.