---

The Diesel Exhaust Filter is a device that is now becoming standard equipment on new diesel powered vehicles. For some the name is misleading. The actual name of the device in use today is called the Diesel Particulate Filter or DPF. This is the filter that removes 85% to 100% of the solid particulates that are produced by the combustion of the diesel fuel.

Why most assume the names are interchangeable is because the DPF removes the visible pollutants so it is interpreted as being filtered. While this is true, the nitrous oxides, carbon monoxides and other gases are still present and not being filtered as the DEF would lead someone to believe.

The flow of the exhaust gases does have to continue for the most part uninterrupted so the engine will perform as needed. The DPF is used to remove the particulates that are a main source of pollutants that cause harm to the humans that are near where the engines are operating. While the gases dilute in the atmosphere, the particulates stay closer to the ground and are inhaled by those around it. This is the reason for the need of their removal and the largest difference between diesel exhaust and gasoline exhaust.

The way a DPF works is simple, by having a large surface area in which the diesel exhaust gases come in direct contact with, the larger particles will not be able to sustain being suspended in the gases and collect on the surface. When a platinum catalyst is present on this surface a chemical reaction can occur that reduces these particulates to less toxic and less harmful substances.

The catalyst alone can’t make this reaction; the introduction of heat must also be maintained. This is the reason the DPF is located just aft of the diesel engine’s exhaust manifold. With the heat and the catalyst, the chemical reaction is able to be maintained and will reduce or eliminate the amount of particulates that reach the end of the tail pipe while the engine is running.

When an engine is equipped with a DPF, the non-toxic chemicals must be periodically cleaned out to keep the gas flow at its maximum efficiency level. Under normal working condition this period is every 6 months.

This is a brief explanation of just what the modern diesel exhaust filter really is and how it helps to clean the air around us that we all breathe.

Related articles

• Diesel Truck Exhaust (epaemissions.com)
• Disposable DPF Diesel Particulate Filter (epaemissions.com)
• Your Diesel Emmission Filter (epaemissions.com)