The Euro standards are a set of emissions regulations mandated by the European Union.

Starting with Euro 1 in 1992, they have become increasingly stringent with each new iteration (Euro 2, 3, 4, 5, 6, and the upcoming Euro 7).

Their primary purpose is to improve air quality by limiting the output of harmful pollutants from vehicle exhausts.

It's important to note that Euro standards regulate pollutants that cause smog and health problems—primarily nitrogen oxides (NOx), particulate matter (PM), hydrocarbons (HC), and carbon monoxide (CO).

They do not directly regulate carbon dioxide (CO2), which is a greenhouse gas linked to climate change, although technologies that reduce pollutants often impact fuel efficiency and thus CO2 as well.

For a vehicle to be sold in the EU, its emissions, measured during the official test procedure (like WLTP), must be below the limits set by the current Euro standard.

The Euro standard a vehicle complies with is a key factor in determining its Crit'Air sticker class in France, directly impacting its access to Low-Emission Zones (ZFE-m).