All active soot filter systems for ships basically work the same way: they increase the temperature in the system. This ensures that the soot is burned off and regenerates the filter. The difference between active and passive soot filter systems is temperature control: - Active soot filter systems artificially raise the temperature within the DPF. - Passive soot filter systems do not need additional heat because the engine produces exhaust gasses at a higher temperature. Passive soot filter systems reach higher temperatures simply with the heat of the exhaust gases. When smaller engines operate at sufficient load, the exhaust gases are often hot enough to burn off the soot. If the exhaust gases are not hot enough to incinerate the soot, an active soot filter system ensures that the soot is burned off. An external fuel burner provides the additional heat needed to convert the soot particles to ash.