Air quality
European Directives: Petrol vapour recovery
Petrol vapour recovery stage 2 (PVR II)
What is PVR II?
Petrol contains volatile organic compounds (VOCs) which evaporate inside the fuel tank of a vehicle and fill the air space above the liquid fuel.
Petrol vapour escapes when drivers fill the empty, or partially empty tanks of their vehicles at service stations. This petrol vapour is forced out from the fuel tank by the incoming fuel and, unless controlled, escapes into the atmosphere through the filler neck of the fuel tank.
Petrol vapour recovery systems can be installed at service stations to reduce the amount of petrol vapour that escapes to the atmosphere from vehicle refuelling; these are known as 'stage II' controls.
Why control volatile organic compounds?
Volatile organic compounds (VOCs) are a precursor to ground level ozone. In sunny, still conditions and in the presence of nitrogen oxides, emissions of volatile organic compounds react to form ground level ozone. This is one of the components of summer time smog and harms human health, vegetation and building materials.
Ozone and its precursors can be transported over long distances and consequently pollution episodes may occur many hundred kilometres from pollution sources.
In the UK the highest levels occur in south-east England due to its proximity to continental sources of ozone precursors. Maximum concentrations generally occur downwind of the precursor pollutant source.
Ozone concentrations are often higher in rural and suburban areas than in urban conurbations. This is due to the complex chemical reaction that causes ozone to form; high emissions of nitric oxide from vehicle exhausts in cities may react with ozone to form nitrogen dioxide reducing local ozone concentrations.
The UK Government and the devolved administrations recognise that because of the transboundary nature of ground level ozone, any reduction of ozone concentrations requires an international approach.
PVR II is an obligation under the UNECE 1991 Geneva Protocol (the ‘VOC Protocol’) concerning the Control of Emissions of Volatile Organic Compounds or their Transboundary Fluxes.
The VOC Protocol is one of eight protocols to the United Nations Economic Commission for Europe (UNECE), 1979 Convention on Long Range Transboundary Air Pollution (CLTRAP)). The Protocol came into force on 29 September 1997. The UK ratified the Protocol on 14 June 1994.
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Page last modified: 30 July 2008