European emission standards for motor vehicles define the acceptable limits for exhaust emissions. Emission standards limit the amount of pollution that can be released into the atmosphere. ...

A series of European Union Directives are staging the introduction, progressively over many years, of increasingly stringent standards for the acceptable limits of vehicle emissions.

These stages were originally refered to as Euro I, Euro II, Euro III, Euro IV, and Euro V, but popular usage has renamed them to the more modern sounding Euro1, Euro2, Euro3, Euro4 and Euro5. Note that Euro I has also been refered to as EC93, and Euro II as EC96. EURO I was the emission standard for cars introduced in the EU in 1992 that limits car emissions to 8 g/kWh of NOX and 0. ... EURO II was the emission standard for cars introduced in the EU in 1995 that limits car emissions to 7 g/kWh of NOX and 0. ... EURO III is the emission standard for cars introduced in the EU in 1999 that limits car emissions to 5 g/kWh of NOx and 0. ... EURO IV is the emission standard for vehicles that will be introduced in the EU in 2005. ... EURO V is a European emission standard for vehicles that will be introduced in the EU in 2008. ... EURO I was the emission standard for cars introduced in the EU in 1992 that limits car emissions to 8 g/kWh of NOX and 0. ... EURO II was the emission standard for cars introduced in the EU in 1995 that limits car emissions to 7 g/kWh of NOX and 0. ... EURO III is the emission standard for cars introduced in the EU in 1999 that limits car emissions to 5 g/kWh of NOx and 0. ... EURO IV is the emission standard for cars that will be introduced in the EU in 2005 that limits car emissions to 3. ... EURO V is the emission standard for cars, succeeding Euro IV, that will be introduced in the EU in 2008 that limits car emissions to 2 g/kWh of NOx and 0. ... EURO I was the emission standard for cars introduced in the EU in 1992 that limits car emissions to 8 g/kWh of NOX and 0. ... EURO II was the emission standard for cars introduced in the EU in 1995 that limits car emissions to 7 g/kWh of NOX and 0. ...

Here is a summary list of the standards, when the come into force, what they apply to, and which EU directives provide the definition of the standard.

Euro I (1993) for passenger cars - 91/443/EEC (also for passenger cars and light trucks - 93/59/EEC) EURO I was the emission standard for cars introduced in the EU in 1992 that limits car emissions to 8 g/kWh of NOX and 0. ...

Euro II (1996) for passenger cars - 94/12/EC (& 96/69/EC) EURO II was the emission standard for cars introduced in the EU in 1995 that limits car emissions to 7 g/kWh of NOX and 0. ...

Euro III (2000) for any vehicle - 98/69/EC EURO III is the emission standard for cars introduced in the EU in 1999 that limits car emissions to 5 g/kWh of NOx and 0. ...

Euro IV (2005) for any vehicle - 98/69/EC (& 2002/80/EC) EURO IV is the emission standard for vehicles that will be introduced in the EU in 2005. ...

Euro V (2008/9) for any vehicle - 99/96/EC (& legislation in draft during summer 2005) EURO V is a European emission standard for vehicles that will be introduced in the EU in 2008. ...

These limits supercede the original directive on emission limits 70/220/EEC

The classifications for vehicle types are defined by 2001/116/EC (amending Directive 70/156/EEC).

Sources: European Environment Agency (http://glossary.eea.eu.int/EEAGlossary/E) Some further detail can be read on http://www.dieselnet.com/standards/eu/ld.html