Background A European Commission working group on environment and health has been set up to develop and discuss new European guidelines for measuring ultrafine particles. Scientists assume that ultrafine particles have a large impact on the environment and human health (some 60 000 fatalities per year in Europe). To date, however, the social and environmental costs cannot be estimated. Reliable data on ultrafine particles is necessary in order to define the scale of the problem and find solutions. The aim of creating a European measuring station network for ultrafine particles can only be realised if cheaper technology (one-fifth the cost of current devices) can be developed. This would support solutions for air quality problems. Objectives The project aimed to demonstrate an affordable ultrafine particle measuring device for pan-European implementation. Prototypes were to be installed at high traffic concentration sites in Dresden and Augsburg (Germany), Stockholm and Prague. The project was expected to provide stable delivery of reliable data, available through a variety of measuring networks, with devices operating over a one-year period. It was also planned to deliver a report on the findings, with the project results being promoted to other institutions, authorities and the general public, as well as to the European Commission working group. Project activities were to be underpinned by a planned series of congresses, fairs and a final conference. Results The UFIPOLNET project developed and demonstrated a reliable and cost-efficient ultrafine particle measuring device. Long term measurement of ultrafine particle number concentrations and size distributions at four different locations (Dresden, Augsburg, Stockholm, Prague) demonstrated the applicability of the device for routine monitoring in Europe. The four prototypes have delivered reliable and comparable data for various kinds of analysis. To produce comparable data, the sampling system was also standardised. It includes a PM10 inlet, a PM1 cyclone, a dryer unit and a critical orifice. The feedback from practical experiences during 12 months of routine measurement in the four cities resulted in several improvements to the instrument. It also helped the beneficiary create a user manual. The monitoring stations in the four cities participating in the project will continue taking measurements after LIFE. The commercial version of the prototype Ultrafine Particle Monitor UFP 330 will soon be available for use in all European measuring networks. It will cost about the same as a common PM2.5 sampler. Other advantages of this reliable instrument are low cost of ownership (both maintenance and personnel) and simple setup and operation, especially when compared with other instruments measuring size distributions of particles. Neither working fluids like butanol nor a radioactive source are needed, eliminating liquid waste, emissions of volatile organic compounds and the risk of handling radioactive materials. The instrument will measure particles between 20 and 500 nanometres in 6 size classes (>20 | >30 | >50 | >70 | >100 | >200 (up to 500) nm), respectively. UFP has not yet reached the status of a measurement method suitable for large-scale routine use in networks, though a number of monitors are running in Europe. For this reason, a high cost-benefit-ratio can be assumed if a standard methodology can be developed. The results of this project will be provided to the working group on “Particulate Matter” of the thematic strategy CAFE (Clean Air for Europe)” of the Sixth Environment Action Programme, which has the objective of supporting the European Commission’s review of the First Daughter Directive (DD) 1999/30/EC. CAFE is one of seven Thematic Strategies foreseen within the 6th EAP. One of its objectives is to achieve levels of air quality that do not give rise to unacceptable impacts on, and risks to, human health and the environment. Further information on the project can be found in the project's layman report (see "Read more" section).