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Major part of the research work on particulate emissions has been carried out at normal ambient temperature (about +23 °C). In real life, the average day temperatures, especially in the winter season, are far below the “normal” temperature of the exhaust emission test procedures. For many years, it has been obvious that the knowledge of the total particulate mass emissions is not enough. Quality of these particles, e.g. polyaromatic hydrocarbon content and mutagenicity, has been studied. Now there is also a need to gain more information on fine particles, which can penetrate lungs more easily. International Energy Agency's Committee on Advanced Motor Fuels sponsored this study of the possible effect of ambient temperature on particle emissions. Also aldehydes and speciated hydrocarbons were studied. Several different engine and fuel technologies were covered, including gaseous fuels and biodiesel. Research work focused on light-duty technologies.

Propane is considered to be a viable fuel alternative for low-emission heavy-duty vehicles in Finland. Natural gas and propane have roughly the same potential for reduced exhaust emissions. Since natural gas and propane are both imported fuels in Finland, there is no preference between these two fuels. Propane, however, is much more easy to distribute, refuel and store onboard the vehicle. This is why propane has received more attention than natural gas as an automotive fuel. Work to develop a low-emission propane fueled truck started back in 1988 with engine tests. The first prototype, a 17-ton SISU truck was built in 1990, and was operated until September 1992. This truck was equipped with a 7.4-liter Valmet-engine, a closed-loop controlled IMPCO-fuel system and a three-way catalytic converter (TWC). The experience with this propane fueled truck was good. The driveability was excellent, and both noise level and exhaust emissions were low.