Onboard refueling vapor recovery

An Onboard refueling vapor recovery system (ORVR) is a vehicle fuel vapor emission control system that captures volatile organic compounds (VOC, potentially harmful vapors) during refueling. There are two types of vehicle emission control systems: the ORVR, and the Stage II vapor recovery system. Without either of these two systems, fuel vapors trapped inside gas tanks would be released into the atmosphere, each time refueling of the vehicle occurred. However, an ORVR system is able to retain those emissions, delivering them to the vehicle's carbon-filled canister and then to dispose of those vapors by adding them to the engine intake manifold and the stream of fuel supplying the engine, during normal operation. The goal behind implementing the ORVR system throughout the U.S. is to eventually make the Stage II systems obsolete.William F. Woodcock, William E. Ruhig, Jr. , and Loren H. Kline hold the patents for the ORVR system.Vehicle ORVR systems have design characteristics that are not compatible with Stage II vacuum assisted systems. When these two systems work in conjunction, the overall efficiency declines significantly, as compared to each system functioning on its own.The vapors which are displaced from the fuel tank by the incoming fuel are routed via the vapor vent line to the canister and are absorbed by activated carbon. These canisters are fabricated from either steel or plastic. The size of this canister is tailored to accommodate expected evaporative emissions. The emissions occur diurnally or throughout the day, even when the vehicle is parked.