The main reason mission critical emergency back up power consumers select active diesel particulate filter technology is reliability.
Active systems are typically electronically controlled with a dedicated programmable logic computer(PLC) that analyzes and controls the operation and performance of the after-treatment device.
An active system will typically monitor the system exhaust back pressure and modify its self cleaning strategy to ensure that the full load capability of the engine is always maintained. Directly heating the soot is the most efficient manner of accomplishing this, but indirect heating solutions that heat the entire exhaust flow of the engine are also available on the market today.
In contrast, passive systems typically rely on human intervention to ensure they are maintained and operated in accordance with the many limitations that dictate their health. Unlike active systems, filter regeneration is dependent on there being enough exhaust temperature coming from the engine to activate the catalyst and ignite the trapped soot. For many applications, the maintenance run time is limited by the operating permit, making it difficult to achieve the light off temperature required to burn soot.
If reliability is your primary goal, be sure to explore all of the operating restrictions of your after treatment options.