Diesel engines have become the “workhorse” of industry. They are the prime power source for many industrial and commercial applications because of their reliability, rugged construction and fuel economy.The presence of particulate matter in the exhaust gas, however, has “tarnished” the diesel engine's image. Soiling, visibility reduction and potential health effects are some of the problems being associated with diesel particulates.Extremely stringent U.S. and European heavy-duty on-highway standards have been implemented, resulting in clean burning diesel engines for truck and bus applications. Some engines are just below, or slightly exceed, the legislated particulate standards.Meanwhile, the U.S. EPA, the State of California and the European countries have developed (or are in the process of developing) exhaust emission regulations for industrial engines, to be implemented in the mid/late 1990s, which also contain particulate standards.Having recognized the need for particulate filters as a retrofit solution for existing engines as well as an after-treatment device for new engines in applications such as city buses or in-door operation of industrial equipment, DEUTZ SERVICE began the development of particulate traps in the mid 1980s. The DEUTZ SERVICE Diesel Particulate Trap System (DPFS) was reported in a technical paper in 1989.This paper provides an overview of present and upcoming emission legislation in North America and Europe and reports on on-going field programs. It also presents the improved DPFS II technology of the full-flow in-line trap system which is offered by DEUTZ SERVICE in production now.