Particles Matter to be published on February 25th, 2022


Quick PN test verifies effectiveness of DPF

While the diesel engine may not pave the way in the energy transition, it will be with us for a long time to come.

Within Europe, approximately 80 million diesel vehicles are fitted with a diesel particulate filter (DPF). Provided they work properly, DPFs reduce emissions of harmful particulates by more than 95%. An impressive achievement that is reversed if the DPF is removed or develops a fault. So how can we test - quickly, reliably and cost-effectively - that a DPF works properly? And how do we embed this test in the Periodic Technical Inspection (PTI)?
By answering 92 questions, Particles Matter explains the PTI-PN test, the Particle Number (PN) counter, and the complex technical ins and out of the DPF. The book is intended for PTI inspectors, mechanics, policymakers and other interested parties.

In 2012, the Netherlands took the lead in developing a new PTI-PN test for diesel vehicles. The test is conducted using an affordable, uncomplicated PN counter capable of measuring high PN concentration levels.
As of 2022, millions of diesel vehicles will undergo a PTI-PN test every year. The Netherlands, Belgium and Germany are the first European countries to introduce the test. It is expected – and certainly hoped - that other countries will follow.


Table of contents.


1.   PTI-PN test - introduction and general description

2.   Basic information on DPFs and particulate emissions

3.   The PTI-PN test in practice

4.   PTI-PN limit values for PN concentration levels

5.   PN counters - types and technical requirements

6.   Working with PN counters

7.   Conducting a PN test - tips and suggestions

8.   Maintenance and recertification of the PN counter

9.   Defective DPFs - causes and consequences

10.  Particulate filter test for petrol vehicles

11.  The PTI-PN test in the Netherlands, Belgium and Germany

12.  International developments


Final personal notes

List of abbreviations

Overview of commercially-available PN counters


The following 92 questions are used to explain the particle test and particulate filter technology in general.


Chapter 1

PTI-PN test - introduction and general description.

• An introduction to the DPF
• From exhaust gas opacity test to PN test
• The PN test
• What is a DPF?
• Why is the (PTI-)PN test necessary? What purpose does it serve?
• How many EU-registered diesel vehicles are fitted with a DPF?
• Who developed the PN test?
• What does the PN test entail?
• How is the PN test conducted?
• What are the technical attributes of a PN counter? Which measuring principles are applied?
• How is a vehicle prepared for the PN test?
• Which particulate emissions will the PN test identify?


Chapter 2

Basic information on DPFs and particulate emissions.

• How effective is a DPF?
• Which particulate types are found in diesel exhaust gas?
• How are soot and particulate emissions measured?
• How are particulate number emissions (PN emissions) measured for the purposes of vehicle type approval?
• Which types of DPF are currently in use?
• Which filter materials are used in a DPF?
• Which components make up a DPF?
• How does a DPF work?
• How large are the openings in the porous wall of a DPF?
• How is a DPF purged or regenerated?
• Why are DPFs occasionally removed and cleaned?
• Under which circumstances do DPFs develop faults?
• Which factors impact the particulate emissions of a diesel engine?
• Are there significant differences between the particulate emissions of diesel-powered passenger cars, light commercial vehicles and trucks?
• How have particulate emissions from diesel vehicles traditionally been measured during the PTI?


Chapter 3

The PTI-PN test in practice.

• How is the PTI-PN test performed in the Netherlands, Belgium and Germany?•
• How is the PN counter powered up and initiated?
• How is the sampling probe placed in the exhaust?
• How long does a PN test take?
• Why is the PN test performed at idle speed?
• How is a vehicle prepared for the PN test?
• Under which standard conditions is the PN test performed?
• Can a PN test be conducted under non-standard conditions?
• Which PN concentration levels are normally encountered?
• How is the average PN concentration level determined?
• What does 'fast-fail' and 'fast-pass' mean, and why are these options included in the test procedure?
• How can variations in the test results arise?
• How does exhaust gas recirculation (EGR) affect engine emissions?
• How does the PN test compare to the exhaust gas opacity test?
• Which steps does the PTI-PN test flowchart include?


Chapter 4

PTI-PN limit values for PN concentration levels.

• How will diesel vehicles fitted with a DPF perform in the new PTI-PN test?
• Which PTI-PN limit values can be expected?
• How strictly will these limit values be applied?
• How will the introduction of the PTI-PN test affect air quality?
• What is the correlation between the PTI-PN limit value and DPF filtration efficiency?
• Which limit values will be applied when the PTI-PN test is introduced?


Chapter 5

PN counters - types and technical requirements.

• Where are the technical requirements for PN counters specified?
• What are the technical attributes of a PN counter?
• Which measuring principles are applied to PN counters?
• Which components does a PN counter consist of?
• Which types of sampling system are used?
• How is exhaust gas conditioned?
• What is the legally required measuring range of a PN counter?
• Which particulate sizes does a PN counter measure?
• What are the requirements for measuring accuracy (maximum permissible error)?
• Within which temperature range can a PN counter be used?
• Can a PN counter be used at higher altitudes?
• How often should a PN counter be inspected (and calibrated)?


Chapter 6

Working with PN counters.

• Can a PN counter be used at different test stations?
• Is there a standard initiation procedure for PN counters?
• Which daily checks should be performed?
• What is the purpose of a HEPA filter?
• What happens if too much or too little exhaust gas is drawn into the PN counter?
• How should the sampling probe be placed in the exhaust?
• How can unnecessary contamination of the PN counter be avoided?


Chapter 7

Conducting a PN test - tips and suggestions.

• Which conclusions can be drawn from carbon deposits in the exhaust system?
• Which parameters affect the outcome of the PTI-PN test?
• Which parameters affect the stability of the measured value?
• Can an additional test be conducted if PN concentration levels measured during the first test are too high?


Chapter 8

Maintenance and recertification of the PN counter.

• Why is a regular recertification of the PN counter necessary?
• To what extent can the measurement results of different certified PN counters vary?
• Why does a PN counter require maintenance?
• What are the recertification procedures for a PN counter?


Chapter 9

Defective DPFs - causes and consequences.

• What is the expected life of a DPF?
• Why do DPFs fail?
• Under which conditions can a DPF fail?
• What happens to the DPF on a vehicle that makes many short journeys?
• How do emission levels evolve over the lifetime of a diesel engine?
• What are the main reasons for higher engine emissions?
• How do higher emissions affect a DPF?
• How does the OBD system detect a defective DPF?
• Which remedial steps should be taken if a defective DPF is encountered?


Chapter 10

Particulate filter test for petrol vehicles.

• Can the PN test also be used for petrol-powered vehicles?
• Can the PN counter be used to analyse exhaust gas from a petrol engine?
• Does the composition of diesel exhaust gas differ from that of petrol exhaust gas?
• How do particle emissions from a petrol engine compare to those from a diesel engine?
• How do emissions from different types of petrol engine relate?
• How does the size of petrol-derived particulates compare to that of diesel-derived particulates?
• Why are petrol vehicles fitted with a gasoline particulate filter (GPF)?
• Which modifications are required to make the PTI-PN test suitable for petrol vehicles?


Chapter 11

The PTI-PN test in the Netherlands, Belgium and Germany.


Chapter 12

International developments.


Total number of pages: 126.