DLPI (Dekati® Low Pressure Impactor) is a 13-stage cascade low pressure impactor to determine particle gravimetric mass size distribution. The size classification in DLPI is made from 30 nm up to 10 µm with evenly distributed impactor stages and can be extended down to 30 nm with an additional back-up filter. 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. Other DLPI characteristics include low inter-stage wall-losses(2 and robust yet easy-to-use operation. The rigid stainless steel construction of the DLPI makes it suitable for a wide variety of applications including power plant and vehicle emission measurements, engine blow-by measurements, air quality studies and pharmaceutical inhalation aerosol device testing.

DLPI features

  • Wide particle size range; 30 nm – 10 μm, 0 nm – 10 μm with filter stage.
  • 12 particle size fractions, 13 with filter stage
  • 30 lpm sample flow rate
  • Robust, stainless steel construction
  • Can be heated up to 200 °C
  • Excellent calibration data(1
  • Low inter-stage wall losses(2
  • Complete measurement solutions for different types of measurement applications available from Dekati Ltd.




(1 Marjamäki, M., Keskinen, J., Chen, D-R. and Pui, D. Y. H. (2000) Performance Evaluation of the Electrical Low-Pressure Impactor (ELPI), Journal of Aerosol Science 31:2, pp. 249-261.

(2 Virtanen, A., Marjamäki, M., Ristimäki, J., Keskinen, J. (2001). Fine particle losses in electrical low-pressure impactor, Journal of Aerosol Science, vol 32, pp 389-401.


DLPI (Dekati® Low Pressure Impactor) is a cascade impactor to measure airborne particles in 13 size fractions between 30 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 200 °C (up to 400 ºC with minor modifications). 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, a pressure meter to monitor impactor low pressure (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 all 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 either be placed inside the flu gas or chimney, or it can be placed outside the stack and heated up to the sample temperature to avoid condensation and sample transformations. The measurement setup in emission measurements includes pump, pressure meter to monitor impactor low pressure (no additional flow control is required), 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.





Nominal airflow
30 lpm
Particle size range
0.030 – 10 µm standard with filter stage extended < 0.030 µm
Number of stages
12 standard 13 with filter stage
Collection plate size
Ø 25 mm for impactor stages
Ø 47 mm for the filter stage
Operation temperature
0 – 200 ºC
5 kg
Ø 65 x 300 mm
Stainless steel
Pump requirements

21 m3/h at 100 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 are presented in the table below.
~ 0


DLPI is a 13-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 100 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.




Filter stage for <30 nm particle collection

DLPI filter stage is a back up filter placed under the other stages of the impactor. The filter stage collects all particles that pass through the other impactor stages, i.e. particles < 30 nm in size and it can be installed into all DLPI units that don’t currently have the filter stage in them. The filter stage upgrade is fully reversible; the DLPI can be used with or without the filter stage after the upgrade. Different types of filters can be used on the filter stage to collect the particles. The filters used on the filter stage are 47 mm in size and the requirements for the filter material are; good collection efficiency for particles < 30 nm and low flow resistance so that the 100 mbar pressure is still achieved above the filter with the vacuum pump. Suitable filters are also available at Dekati, and recommendations for suitable filter-pump combinations at support@dekati.fi.

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@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.

Collection plate set

A spare set of collection plates is available for all DLPIs. The set includes 13 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. The collection plates are numbered from 1 to 13.

Impactor Heating Assembly

DLPI impactor can be heated up to 200 ºC with the DLPI impactor heating jacket. The heating jacket is wrapped around the impactor and adjusted to a desired temperature with a digital temperature controller. The controller also includes overheat protection.

Other DLPI accessories Include:

DP25 230/50Hz EUR, for 10 and 30 lpm impactor IA-904              
DP25 100V/50Hz JPN, for 10 and 30 lpm impactor IA-905
DP25 115/60Hz USA, for 10 and 30 lpm impactor IA-906
DP65 230/400V 50Hz and 230/460V 60Hz EUR, for 30 lpm impactor IA-264
DP65 200V 50/60Hz USA/JPN for 30lpm impactor IA-265
Sampling cyclone for separation of particles > 10 µm SAC-65
Sampling nozzles for isokinetic sampling
PM10 inlet for ambient sampling  
10 lpm IPR-227
30 lpm IPR-127


Dekati® Low Pressure Impactor brochure


Available in customer pages section:
          DLPI Manual
          Data processing spread sheet
          Spare part catalogue


Can’t find what you’re looking for?

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

Contact Dekati sales at sales (at) dekati.fi



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