Definition(s)
Oil-immersion “o”
Type of protection in which the electrical equipment or parts of the electrical equipment are immersed in a protective liquid in such a way that an explosive gas atmosphere which may be above the liquid or outside the enclosure cannot be ignited.
Source: IEC 60079-14:2013, Explosive atmospheres – Part 14: Electrical installations design, selection and erection, Edition 5.0, November 2013. Global Standards