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REGEN stands for Regeneration.

DPF Regen is:

the process by which the soot within a diesel particulate filter (DPF) is converted to ash through the use of heat, chemical reaction and or electricity. Soot combustion temperatures range from the 250˚C – 350˚C range (with a chemical or fuel catalyst) to the 550˚C range (without catalyst).

In this article, we go over the basics of what is a DPF regen, the different aftertreatment filters, and what they do. We will also cover the different types of regens.

DPFs catch, store & oxidize soot, then store ash

Diesel Particulate Filters (DPFs)

are designed and required to have at least an 85% particulate matter reduction from the air; oxidizing particulates either passively (while the vehicle is driving down the road) or actively (through a heat, fuel, or electric source), effectively “regenerating” the DPF. REP has a full lineup of OEM replacement DPFs.

Diesel Oxidation Catalysts (DOCs)

generally are placed before a DPF – this device uses a catalyst to help create the correct environment to allow soot to regenerate within a DPF. REP has a full lineup of OEM replacement DOCs.


happens while driving, without driver initiating

Typically happens as you’re driving down the road; when the DPF light comes on, that’s an indication of “passive regen”. See the light with the 8 dots and a symbol that looks like a check engine light? This indicates the exhaust gas is hot, the exhaust itself is hot and the tailpipe is hot – do not touch it or pull over, and keep driving if you’re able. DO NOT park in TALL or DRY GRASS while truck is in REGEN mode.

DPF systems that use passive regen use a chemical coating – or catalyst (such as precious metals) – along with exhaust gases to heat up the exhaust stream for soot oxidation. As the engine heats up and exhaust stream is moved through the engine into the diesel oxidation catalyst (DOC), a chemical reaction happens between the exhaust gasses and the catalyst; the DOC temperatures increase, then the heated exhaust stream flows into the DPF and oxidizes the soot, creating ash that is then removed through servicing the DPF.


a regen that is initiated by the driver, does not happen automatically

Active-only systems are rare, usually aftermarket – they use diesel fuel or electricity as a heat source to oxidize soot; typically done while parked and is driver initiated.


most trucks have this type of regen capability

Trucks that utilize passive-active regeneration are able to both regen on the truck while driving down the road AND through forced regen initiated by the driver. Forced regen is required – let’s say – after the driver has sat in traffic for an extended amount of time and the “service DPF” light comes on…. this means the duty cycle isn’t hot enough for regeneration while driving down the road, so it’s prompting for the driver to manually initiate regen.


regeneration is key for really cleaning your DPF

So we’ve learned that heat is a necessary element in the regeneration process, and we’ve learned about the various types of regen. But regen doesn’t stop on the truck…. the reason that DPFs need cleaning at all is that the on-truck regen process produces ash that accumulates and eventually plugs the DPF, leading to potential engine problems and poor fuel economy.

Cleaning the DPF while off the truck IS another type of regen. Same physics, using the same method; heat. Why is baking so crucial to the cleaning process? Because on-truck regen doesn’t break down ALL of the soot in a diesel particulate filter, except under perfect conditions, which rarely exist.

Removing the DPF from the vehicle and then Baking the DPF is the most consistent way of breaking down soot to ash, and allows for proper cleaning of the DPF, which leads to prolonged operation and peak efficiency of the emissions system and engine.

The only DPF oven on the market that’s made specifically FOR DPF cleaning is the Filtertherm® DPF Thermal Oven! Not only that, but it’s designed to bake multiple DPFs at once, and has OEM-approved heat settings already pre-programmed in, making DPF cleaning easier and safer than ever. Baking the DPF in the cleaning process ensures that your shop will get consistent results and that the DPF is as clean as possible.

See how the Filtertherm DPF Thermal Oven works.

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Want to find out about becoming a Redline Emissions Products® dealer?

Contact Wayne Cochrane, National Sales Manager for REP to find out more.  Call 888-295-4670

Need Tech Support or need help troubleshooting a DPF problem? No problem! Contact REP Support at 1-888-564-4209