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Currently, regulations on vehicle evaporative emissions only focus on the sum of Total Hydrocarbons (THC) without taking into account either the detailed hydrocarbon composition nor other chemicals besides hydrocarbons emitted from gasoline evaporation. As a consequence, this composition, also known as speciation, is not always noted and is even more unknown when biofuels such as ethanol are introduced in the market. Furthermore, these regulations do not differentiate the source of these emissions in the vehicle. The programme described in this paper is designed to investigate the influence of the addition of ethanol to gasoline on evaporative emissions. It has tried to go one step ahead of these directives obtaining more detailed characterization of these evaporative emissions.

Current regulations on exhaust automotive emissions focus on certain pollutants to control vehicle emissions. Hydrocarbons, the main components of gasoline, are one of these regulated compounds; however, the regulation only refers to the sum of total hydrocarbons (THC) without taking into account the individual components. Vehicles also emit a large variety of chemical besides hydrocarbons that can become much more harmful, depending on their environmental toxicity and the amounts that are emitted to the atmosphere. In recent years, due to the emergence of alternative fuels such as bioethanol and biodiesel, the interest in these not so well characterized compounds has grown. For example, when ethanol is used in gasoline blends as a fuel for internal-combustion engine vehicles, the study of other compounds such as alcohols, aldehydes and ketones, in addition to hydrocarbons, acquires more importance.

Ethanol fuel is a sustainable energy resource that is intended to provide a more environmentally and economically friendly alternative to petroleum-based fuels, such as gasoline. Recent interest in ethanol has increased due to the fact that it can be combined with gasoline at different percentages: from low percentages with not specially modified gasoline vehicles up to 85% of ethanol, and even up to 100%, in flexible-fuel vehicles. There is much debate and a considerable amount of concern among automakers and consumers regarding the environmental friendliness of ethanol, mainly due to the lack of complete knowledge about the effects of its use on direct pollutants from exhaust vehicle emissions such as CO, CO₂, NOx, HCs and particulates and on the fuel consumption of the vehicle.