EN3 is a European standard governing portable fire extinguishers, established by the European Committee for Standardisation. Adherence to this standard is a legal necessity for manufacturing all fire extinguishers within the European Union. In the UK, certification of this standard is overseen by the British Standards Institution.

The EN3 standard serves to guarantee that fire extinguishers are suitable for their intended use. They are constructed to withstand pressure fluctuations and other atmospheric or physical changes that could otherwise impede the proper functioning of an extinguisher.

EN 3 supersedes the older BS 5423:1987 standard, which was withdrawn in 1997. Prior to this change, the UK employed a distinct color coding system to differentiate between various types of fire extinguishers. According to BS EN3, a minimum of 95% of the extinguisher body must be colored red, with only 5% allocated for color-coded zones.

BSI, as a business standards organization, assists companies in cultivating a culture of excellence globally. It serves as the National Standards Body for the UK, representing the country at ISO, IEC, CEN, CENELEC, and ETSI. Established in 1901, BSI holds the distinction of being the world's first National Standards Body.