DLPI+ (Dekati® Low Pressure Impactor) is a 14-stage cascade impactor to measure airborne particle mass size distribution. The DLPI+ classifies particles into 14 size fractions in the range of 16nm-10µm. In each size fraction the particles are collected on 25 mm collection substrates that are weighed before and after the measurement to obtain gravimetric size distribution of the particles. A chemical analysis of the size classified particles can also be performed. The DLPI+ impactor can be used in various particle measurement applications and can also be heated up to 180 °C for high temperature applications.



DLPI+ features

  • Particle Size distribution in 14 size fractions
  • Wide operational range of 16 nm – 10 µm
  • Particle collection area Ø25 mm
  • 10 lpm sample flow rate
  • Integrated impactor low pressure (40 mbar) measurement and adjustment
  • Can be upgraded into a full ELPI®+ system for real-time data
  • Well characterized impactor with low inter-stage particle losses*
  • Each unit manufactured and calibrated in Finland
  • Provided with a data processing spread sheet
  • Simplified, robust structure
  • Stainless steel stages for operation even in harsh environments
  • Standard DLPI+ for up to 50 °C measurements
  • Sampling from up to 180 °C with the high temperature upgrade kit

* Järvinen, A., Aitomaa, M., Rostedt, A., Keskinen, J. & Yli-Ojanperä, J. 2014. Calibration of the new electrical low pressure impactor (ELPI+). 2014. J. Aerosol Sci. 69, pp. 150-159.


DLPI+ (Dekati® Low Pressure Impactor) is a new version of the DLPI cascade impactor to measure airborne particles in 14 size fractions between 16 nm and 10 µm. The impactor has a simple and robust structure and it can be used in any application where particles <10 µm exist in the sample. The stainless-steel design enables sampling directly from high temperature sources and heaters can be used to heat the actual impactor unit up to 180 °C. Typical applications for the DLPI impactor include air quality monitoring and emission measurements from stationary sources.

Air quality measurements

The Dekati® Low Pressure Impactor+ can easily be applied to air quality measurement to measure particle size distribution both in indoor and outdoor air. The measurement setup in air quality measurements is simple to use and includes a pump (no additional flow control is required) and a TSP or PM10 inlet, all available from Dekati Ltd. Either aluminium or polycarbonate foils can be used on the impactor stages as a particle collection surface depending on the preferred particle analysis method. The required sample collection times depend on the PM levels in the air and also on the sensitivity of the particle analysis method; typical sampling times are around 1-7 days.

Emission measurements

DLPI+’s stainless steel and robust design makes it an ideal choice for stationary source emission measurements and other applications where the particle sample is in high temperature. The impactor can be heated up to the sample temperature to avoid condensation and sample transformations. The measurement setup in emission measurements includes pump (no additional flow control is required), high temperature sampling kit including impactor heater with temperature control, isokinetic sampling line and needed connections which may vary depending on the dimensions of the measurement location. If large amount material >10 µm exists in the sample, the Dekati® Cyclone can be applied in front of the impactor to collect these large particles that could otherwise interfere with the particle size classification inside the impactor unit. The Dekati® Cyclone withstands temperatures up to 600 °C and can therefore either be placed inside the stack or outside the stack heated. All accessories to make a complete measurement setup are available from Dekati Ltd.

                 DLPI+                                                                            High Temperature DLPI+  


Nominal airflow
10 lpm
Particle size range
0.016 – 10 µm
Number of stages
Collection plate size
Ø 25 mm
Operation temperature
0 – 50 ºC
0 – 180 ºC with the high temperature kit
Stainless steel impactor stages
Pump requirements*
20 m3/h at 40 mbar
Each DLPI+ impactor is individually calibrated before delivery; the calibration includes detailed determination of the exact sample flow rate and D50% values. The nominal values at 20 °C are presented in the table below.
Impactor cutpoints



DLPI+ is a 15-stage cascade low pressure impactor for gravimetric particle size distribution analysis. An impactor has two co-linear plates; one acts as a collection surface for the particles, the other one has small nozzle or nozzles in it to control the flow velocity. The sample flow is first led through the nozzles to achieve a certain, exact flow velocity. After the sample passes through the nozzles it is turned sharply before the collection plate; particles larger than stage cut diameter cannot follow the flow stream lines but are impacted on the collection plate. Particles smaller that the stage cut diameter continue to the following impactor stages where they are further size classified and collected. By changing the dimensions in each impactor stage, different sized particles can be collected on different impactor stages. The flow through the DLPI+ impactor is controlled with the lowest stage jet plate which acts as a critical orifice when 40 mbar is adjusted under the first impactor stage which also means that no additional flow control unit required to operate the unit.

Before the measurement a collection substrate is placed on each of the impactor stages and this substrate is weighed before and after the measurement to determine particle size distribution. Depending on the used substrate material, a chemical composition of the collected particles may also be determined after the sample collection. The substrates used on the collection plates as particle collection surface are 25 mm in diameter and different material substrates can be used depending on the used particle analysis methods.


Collection substrates

Different types of collection substrates can be used on the DLPI+ impactor collection plates. The collection plates used in the DLPI+ are designed for 25 mm substrates and Dekati offers aluminium and polycarbonate substrates for this purpose. For the suitability of different types of substrates, please contact support (at) dekati.fi.


Dekati® Collection Substrate Spray

The collection substrates are often greased in impactor measurements to prevent particle bounce and blow-off from the impactor stages. The Dekati® Collection Substrate Spray is developed to grease the substrates faster and more evenly than with the traditional greasing methods. When used together with a stencil, the Dekati® Collection Substrate Spray enables an easy and fast way of applying a thin and smooth layer of grease on the collection substrates. The grease used in the spray is non-volatile also at low pressures and is therefore suitable for use in low pressure impactors, and also chemically pure enough to enable most chemical analysis to be done from the substrates. Stencils are available for 25 mm substrates that are used in the ELPI®+, High Resolution ELPI®+, High Temperature ELPI®+, ELPI®, DLPI+, DLPI and Dekati® PM10 impactors. Dekati also provides high temperature grease for application where the temperature of the impactor/sample is >100 °C.


Collection plate set

A spare set of collection plates is available for all DLPI+ units. The set includes 14 pcs of collection plates in a carry case. The spare plates have exactly the same design as the existing plates in the DLPI+, and they can be used for fast changing of the collection foils; instead of just changing the foil, the whole collection plate can be replaced with the spare one.


DLPI+ High Temperature Kit

DLPI+ impactor can be heated up to 180 ºC with the DLPI+ High Temperature Kit which includes a heatick jacket for the impactor and integrated temperature control unit. The heating jacket is wrapped around the impactor and adjusted to a desired temperature with a digital temperature controller integrated at the base unit of the DLPI+ impactor.






Other DLPI+ accessories include:

DP25 230V/50Hz EUR, for 10 and 30 lpm impactor 
DP25 100V/50Hz JPN, for 10 and 30 lpm impactor  
DP25 115V/60Hz USA, for 10 and 30 lpm impactor
Sampling cyclone for separation of particles > 10 µm
Sampling nozzles for isokinetic sampling
PM10 inlet for ambient sampling, 10 lpm

Dekati® Low Pressure Impactor+ brochure


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Contact Dekati technical support at support (at) dekati.fi

Contact Dekati sales at sales (at) dekati.fi







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Related products:
High Temperature ELPI®+
High Resolution ELPI®+