The APK (MOT) particle test: what does it mean for your diesel?

The particle counter test is a measurement during the APK that checks whether the DPF of a diesel still works properly. A DPF (in Dutch: roetfilter or partikelfilter) captures the fine soot particles from the exhaust gas. According to research by the Dutch research organisation TNO, quoted by the ANWB (the Dutch motoring organisation), a properly working filter reduces the soot emissions of a diesel passenger car by 95 to 99 per cent.

Until 1 January 2023, the inspector only checked the DPF visually. A filter that was broken inside or had been emptied did not show up that way. With a particle counter the inspector now measures how many particles actually come out of the exhaust. According to the Dutch government (Rijksoverheid), the DPF test has been a compulsory part of the APK since 1 January 2023, and all diesel vehicles with a DPF must pass it. The RDW, the Dutch vehicle authority, says the same in English on its page about the Periodic Technical Inspection.

The test was first planned for 1 July 2022. According to the Government Gazette (Staatscourant), that date was postponed to 1 January 2023 because suppliers could not deliver the particle counters in time.

The particle counter test applies to diesels that have a factory-fitted DPF. The regulation (Staatscourant 2021, 2214) covers passenger cars, commercial vehicles and buses with a diesel engine and a factory-fitted DPF. A van with such a filter therefore gets the test too. The regulation makes no distinction by Euro class or year of manufacture. What counts is whether the car had a DPF fitted at the factory.

Sources: Staatscourant 2021, 2214 and 2022, 16212, and Rijksoverheid. According to Rijksoverheid, the soot measurement applies to diesels without a DPF built from 1980, and the four-gas test to petrol and LPG cars with a closed-loop catalytic converter built from 1993.

You can check whether your diesel has a factory-fitted DPF in the RDW’s registration number check (in Dutch: kentekencheck) at ovi.rdw.nl, where you enter the registration number of the car. Under the environmental data (milieugegevens) you will find “Af Fabriek Roetfilter APK” with ja (yes) or nee (no). According to the ANWB, the DPF became compulsory on new diesel cars in 2011 to meet the European emission standards. A diesel from before 2011 can also have a DPF. Not sure? Call us with your registration number.

For a diesel hybrid too, what counts is whether the car has a factory-fitted DPF. For a van registered as a commercial vehicle (grey number plate, up to 3,500 kg), you can read more on our page about the APK for a van.

The limit is 1,000,000 particles per cubic centimetre of exhaust gas, measured with the engine idling. That is set out in the Dutch Vehicle Regulations (Regeling voertuigen), as amended in Staatscourant 2021, 2214. A properly working filter captures nearly all particles and stays far below that limit. A broken or removed filter goes well above it.

Earlier plans also included a stricter limit of 250,000 particles per cubic centimetre for diesels first registered after 31 December 2014. That stricter limit was dropped in the same amendment. All diesels with a DPF now have the same limit of 1,000,000.

1. The car is stationary and the engine is idling. According to the regulation, the engine can be cold or warm.
2. The inspector puts the probe of the particle counter into the end of the exhaust. If the car has more than one outlet behind a particulate filter, the regulation requires a measurement at each outlet.
3. After a stabilisation time of 15 seconds, the particle counter records the number of particles per cubic centimetre for at least 15 seconds.
4. If the value stays below 1,000,000, the DPF passes. If the value is above it, it is a rejection point (afkeurpunt).

An APK station must have a particle counter to inspect a diesel with a DPF. According to the Staatscourant, the RDW system blocks the registration of the result for such a diesel if the station has no particle counter. A diesel whose DPF has been removed from the RDW records is inspected as a diesel without a DPF. Autobedrijf Willemsbrug is an RDW-approved APK station and carries out the particle counter test itself.

A diesel fails when the DPF lets particles through. A full or clogged filter is usually not the cause, because a full filter still holds the particles back. In most cases the filter is damaged or exhaust gas is getting past the filter.

A rejection point appears on your inspection report. What the different points on that report mean is explained in our article on rejection points, repair points and advisory points.

A DPF that is not working properly often gives signs while you drive. According to the ANWB, an engine that runs poorly and a warning light that comes on are the best-known signs. Look out for these:

If a warning light is on, have the fault code read. Then you know whether it is the DPF, a sensor or something else. You can read more on our page about the engine warning light and in our article on the engine warning light and the APK. An AdBlue warning is something else. AdBlue reduces nitrogen oxide emissions and has nothing to do with the particle counter test.

If your diesel fails the particle counter test, the cause must be fixed before the car can pass. At our garage, the mechanic first looks for the cause. Is the filter broken, is there a leak in the exhaust or is there a fault? After that you receive a quote in advance, and we only carry out repairs with your approval.

The cost depends on the cause. A leak in the exhaust is a different repair from a broken filter. According to the ANWB, replacing a DPF can cost € 1,500. If your car failed at our garage and we carry out the repair, the retest is included. You can read more about the steps after a failure on our page about a failed APK and repairs.

According to the RDW, for a passenger car with a date of first admission before 1 January 2017, you can have the details of the factory-fitted DPF removed from the vehicle records. Different dates apply to commercial vehicles. The car will then no longer fail on the DPF, but according to the RDW you do pay a particulate surcharge (fijnstoftoeslag) on the Dutch road tax (motorrijtuigenbelasting). Read the conditions on the RDW website before you choose this.

At Autobedrijf Willemsbrug, the APK for a diesel with a factory-fitted DPF costs € 60, including the particle counter test. For a diesel without a DPF and for an LPG car, we tell you the price in advance.

Registering the result with the RDW is included.

With a major service, the APK is free at our garage, except for Tesla and Polestar. We do the APK Monday to Friday, by appointment. You can read what else the inspection involves on our page about the APK for all makes.

Look it up in the RDW’s registration number check at ovi.rdw.nl. Under the environmental data you will find “Af Fabriek Roetfilter APK” with ja (yes) or nee (no). If it says ja, your diesel gets the particle counter test at the APK.

No. The soot measurement measures how dark the exhaust gas is and is meant for diesels without a DPF. The particle counter test counts the number of particles per cubic centimetre and is meant for diesels with a DPF.

No. An APK station needs a particle counter to inspect a diesel with a DPF. Without one, the station cannot register the inspection of such a diesel with the RDW.

Yes. The regulation applies to passenger cars, commercial vehicles and buses with a diesel engine and a DPF. A van with a DPF therefore also gets the particle counter test.

That depends on the measurement. The light itself does not tell you whether the filter lets particles through. Do have the fault code read before the APK, so you know what is going on.

No. AdBlue reduces nitrogen oxide emissions, and the DPF captures soot particles. If you have an AdBlue warning, read our article on AdBlue faults (in Dutch).

• Rijksoverheid (Dutch government): Wat wordt er gekeurd bij de Algemene Periodieke Keuring (APK)? (in Dutch)
• Staatscourant (Government Gazette): Wijziging Regeling voertuigen: roetfiltertest met deeltjesteller (Stcrt. 2021, 2214) (in Dutch)
• Staatscourant (Government Gazette): Wijziging Regeling erkenning en keuringsbevoegdheid APK: deeltjesteller (Stcrt. 2022, 16212) (in Dutch)
• ANWB: APK voor dieselauto’s: roetfilter wordt gemeten (in Dutch)
• RDW: Gegevens roetfilter verwijderen (in Dutch)