Onboard Refueling Vapor Recovery (ORVR) is a vehicle emission control

Automobile emissions control

Vehicle emissions control is the study and practice of reducing the motor vehicle emissions -- emissions produced by motor vehicles, especially internal combustion engines....

 system that captures fuel vapor

Vapor

A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....

s from the vehicle gas tank during refueling. The gas tank and fill pipe are designed so that when refueling the vehicle, fuel vapors in the gas tank travel to an activated carbon

Activated carbon

Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...

 packed canister, which adsorbs the vapor. When the engine is in operation, it draws the gasoline vapors into the engine intake manifold to be used as fuel. ORVR has been mandated on all passenger cars in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 since 2000 by the United States Environmental Protection Agency‎. The use of onboard vapor recovery is intended to make vapor recovery

Vapor recovery

Vapor recovery is the process of recovering the vapors of gasoline or other fuels, so that they do not escape into the atmosphere...

 at gas stations obsolete.