Exhaust emission standards

“Euro” terminology is used to describe European emission standards for vehicles, however this term is often used with reference to fuel quality standards. The emission standards are regulated by EU legislative acts which state the progressive introduction of gradually more stringent requirements for nitrogen oxides (NOX), hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM). The stages are referred to as Euro 1, Euro 2, Euro 3, Euro 4, Euro 5 and Euro 6 for light-duty vehicles or LDVs (Arabic numerals), and Euro I, Euro II, Euro III, Euro IV, Euro V and Euro VI for heavy-duty vehicles or HDVs (Roman numerals). Standards for both categories (LDVs, HDVs), and for vehicle types under these categories, differ in permissive levels of emissions (which ar