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Current EPA and CARB regulations allow a maximum of 2.0 g/test for Hot Soak + Diurnal evaporative emissions. The State of California has adopted LEV II regulations that will decrease the evaporative emissions standard to 0.5 g/test starting in the 2004 model year. These regulations also include a Zero Emission Vehicle or ZEV program. The ZEV program allows car manufacturers to substitute vehicles that meet the SULEV tail pipe emission standards and have zero fuel evaporative emissions for electric vehicles. The increased stringency of these regulations has necessitated significant decreases in hydrocarbon emissions from evaporative emission canisters. For example, canister vent emissions may be at levels of 100-300 mg/test for a vehicle that meets the current regulations. However, canister emission targets should be 50 mg/test and less for LEV II and 10 mg/test and less for zero evaporative emission vehicles.

Methanol-gasoline blends have attracted a great deal of attention as automotive fuels for both environmental and economic reasons. To better understand the effect of methanol concentration on activated carbon performance, cycling tests with new carbons and several different methanol:gasoline ratios were undertaken. The data obtained indicate that the keys to activated carbon performance with methanol-blended fuels are the pore size/volume characteristics. It was determined that the working capacity to breakthrough for methanol blends of 0, 10, and 35% by volume were similar but that the working capacity for 85% methanol was significantly lower. When the same carbon was cycled sequentially with gasoline and different concentrations of methanol, the adsorption/desorption performance tended to adjust or recover to levels expected.