Increased use of biomass, especially wood, may play an important role in the efforts to reduce the CO₂-production. Small wood fired furnacs below 70kW, however, are an important source of fine particle emissions and will be even more so in the coming years. This situation has been foreseen already six years ago. Therefore a project was started in 1999 with the aim to develop an exhaust gas aftertreatment system for these small appliances.
A recent study for the European Commission confirmed the important role of smallscale combustion installations. It is also well known that increased concentrations of fine particles in ambient air are the cause for health problems, particularly pulmonary diseases but also cardio-vascular symptoms. A WHO study from 1999 gave an assessment of the consequences of the air pollution in Austria, France and Switzerland in terms of health effects and related economic costs. Another recent study showed that air pollution causes a significant number of premature deaths in nearly all European countries. Particulate matter in ambient air is one of the important pollutants.
For these reasons, there is an ongoing discussion how further regulations concerning the limits for fineparticle concentrations or other efforts might help to improve the situation. In public perception diesel engines are usually considered to be a most important source of air pollution regarding PM₁₀. Upon closer examination of the matter, however, it becomes obvious that emissions from small wood fired furnaces may sometimes play an even more important role. Today this finding for the annual PM₁₀ emissions in Switzerland can be derived by evaluating statistical data that are available for Switzerland. Emissions from small wood fired appliances appear even more important when considering that their emissions occur locallyconcentrated  in residential areas and furthermore these emission are concentrated during the winter season.
For these reasons the EMPA departement “combustion engines and furnaces” has worked on this topic for some years. With support from the BFE and the BUWAL a technical solution has been developed in order the reduce ePM10 emissions from small wood fired appliances.
A  particle separator has been developed that is based on the principle of electrostatic precipitation, but has been simplified to the extent where an inexpensive and easy maintanable solution can be provided that is also suitable for retro-fitting. Numerous laboratory tests as well as extended periods of operation in real world installations have confirmed die effectivity of the system.