Clean Soot Particle Filters (IMAGE) Fraunhofer-Gesellschaft Caption A researcher checks whether the soot particle filter is freed from soot even at exhaust temperatures of 140 degrees Celsius. Credit Fraunhofer ISE Usage Restrictions The picture may be used for editorial purposes only. It is protected by copyright. The use is free of charge if the reference is mentioned. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.