Impactor Johnas - Paul Gothe GmbH

Paul Gothe Bochum 

GMU-Cascade Impactor 

Johnas II 

For In-Stack 

PM 10 and 2,5 

Measurements 

(Emissions Monitoring) 

3 cut-off-classes: 

1. dae > 10 µm 

2. dae 2,5 bis 10 µm 

3. dae < 2,5 µm 

� calibrated with mono- und 

polysize Particle 

� checked for their correctness 

in official control-programs 

according to the german and european guideline 

Developed by 

Gerhard-Mercator University Duisburg 

and contry-environment-office 

Nordrhein-Westfalen –Germany- 

Manufacturer: Paul Gothe Bochum

Johnas II page 2 

Instruction manual PM 10 / PM 2.5 - GMU-Cascade Impactor Johnas II 

for measurement of the emissions of fine dust in low range 

Cascade Impactor GMU-Johnas - developed for PM 10 / PM 2.5 in-stack measurements 

Preliminary Note 

With dust emissions, particular attention should be paid to the proportion of fine dust, which 

may considerably affect the quality of the air. Reference has to be made in this connection to 

the thoracic penetration, the low sedimentation velocity in the atmosphere and the concentration 

of heavy metals on small particles. 

For the above mentioned reason the total and the fine dust content of industrial waste gases 

have been limited by the Technical Instructions on Air Quality Control within the European 

Immission Control Act, in which fine dust refers to particles having diameters of 5 µm and/or 

10 µm. However, nothing has been stipulated as to how particle diameters have to be defined, 

what density the definition has to be based on and which method of measurement has 

to be applied. 

The German Guideline VDI 3491 Part 1 defines 19 different particle diameters. In combination 

with various units of quantity, such as the number, volume and mass, numerous ways 

are obtained for measuring and presenting the particle size distribution. For emission measurements, 

the aerodynamic diameter is suitable for defining the particle size. It describes the 

behaviour of gas-borne particles having a diameter of more than 0.5 µm. In accordance with 

European standards mass fractions should be used for describing the particle size distribution. 

The number of applicable methods of measurement is limited by the requirements of the 

measuring test to be solved. In general it is desirable to measure the particle size while the 

particle is still suspended in the gas. However most measuring instruments used for this purpose, 

such as those based on light scattering, diffusion batteries, electrostatic aerosol analysers 

and aerosol centrifuges, require sampling by means of the extraction probe, since the 

instruments cannot be used directly in the waste gas duct. 

It has been fond that measuring of particles larger than 3 µm is affected by parts of the dust 

being deposited on the walls of the probe and of the measuring instrument inlet. The application 

of these methods of measurement is therefore limited to particles below 3 µm. For emission 

measurements in industrial plants, the presence of particles smaller than 1 µm and up to 

100 µm is to be expected. 

Normally, the above mentioned aerosol instruments cannot be used in hot and chemically 

aggressive waste gases. Heavy cooling of the extracted sample gas stream is not allowed 

since condensation of the moisture and other substances carried along with waste gas could 

alter the particle size spectrum. 

According to the latest state of the art, cascade impactors are considered as suitable for the 

extraction and simultaneous fractionation of sample gas streams for the purpose specified in 

Guideline VDI 2066 Part 1. Moreover, they can be used directly in hot and chemically aggressive 

gases. 

Due to the new standards of ambient air quality PM 10 and PM 2.5, these particle size 

fractions should also be measured in emissions as combustion and industrial processes are 

anthropogenic sources of particulate matter in ambient air. Therefore, the johnas a sampling 

system for PM 10 / PM 2.5 in-stack measurements was designed and calibrated. The 

exhaust gas is isokinetically sucked into the cascade impactor through the inlet of the plane


filter device (VDI 2066 part 7) and the aerosol is fractionated in the particle size classes > 10 

µm, 10 - 2.5 µm and < 2.5 µm. Due to a relatively high volume flow (ca. 3.2 m³/h, depending 

on exhaust gas conditions), sampling times are kept short (for dust concentrations of 10 

mg/Nm³ only 30 min). 

When applying cascade impactors johnas in combination with gravimetric evaluation, it is 

possible to obtain the mass distributions related to the aerodynamic particle diameter. This 

is, however, no substitute for the measurement of the total dust content (TSP). 

Conversion to other particle measures can only be carried out in exceptional cases and with 

the help of additional information on further properties, such as mass density and particle 

shape factors of the dust. 

As with all aerosol measuring instruments, limits are set to the applicability of cascade 

impactors by the particle size range, the mass concentration of particles and the properties of 

the carrier gas. Depending on the condition of the gas, the particle properties, and the design, 

cascade impactors johnas will collect the particles and segregate them into three fractions 

-> PM 10, PM 10 and PM 2.5-. Coarser particles (larger than 10 µm) affect the fractionating 

process and separate often in the first cone (transition between sampling probe and 

first impactor stage). 

The use of the johnas is, of course, not limited to the applications described in this manual. 

Thus, for instance, impactors may be used in field of the process technology. 

1 Principle of the Method 

Impactors make use of the different inertia of particles to fractionate the dust according to 

particle sizes. The basic impactor stage components are the nozzle and impact plate. When 

accelerated in the nozzle those particles which have sufficient inertia strike the impact plate 

where they are collected. 

The most important dimensions of the system as far as fractionation is concerned are the 

nozzle width D, the nozzle length L and the distance S between impact plate and nozzle. 

The cascade impactor Johnas consist of a series of impactor stages in which the particles 

are segregated according to their decreasing inertia, so that fractions of different particle size 

are obtained. The particles which are not retained in one of the impactor stages are collected 

in a backup filter arranged downstream of the impactor stages. 

It is very easy to find out the particle size range covered by the three fractions. Use the excel 

file, which you find in the delivery capacity. The separation efficiencies is a function of the 

particle sizes for the individual impactor stages of a cascade impactor. The probability of a 

specific size of particles being collected on the impact plate and retained there is reflected by 

the separation efficiency which is given by the product of the impaction and retention efficiency. 

The separation efficiency will only equal the impaction efficiency, if the retention efficiency is 

100%. The impaction efficiency depends on the flow field and particularly on the mobility of 

the particles. The flow field is mainly characterised by the S/D ratio and the Reynolds number. 

The particle movement in the flow is defined by the dimensionless Stokes number. 

The Johnas is developed according to the theory of Marple. VA. Marple and B. YH. Liu calculated 

the impaction efficiencies for different flow fields as a function of the Stokes number. 

According to these calculations the impaction efficiency for L/D > 0.25, 0.5 < S/D


mately 80% it rises with a very steep gradient as a function of the Stokes number continuing 

then with a decreasing gradient until reaching 100%. 

Because of the impaction efficiency rapidly rising with the Stokes number, the functional interrelation 

can be expressed more or less as a discontinuous function with the jump discontinuity 

being assigned to the median value St50. This causes a segregation into two fractions at 

the aerodynamic diameter 

The following theoretically derived values, which have also been experimentally confirmed 

for test aerosols, are indicated for various Stokes numbers. 

Median values of the Stokes number determined by experiments are used as a basis for the 

practical evaluation of impactor measurements while the cut diameter dae50 of an impactor 

stage is determined in accordance with equation. 

The influence of the Reynolds number on the median value St50 may be neglected within the 

range of 100 < Re < 3000. 

With very large Reynolds numbers (Re> 10000) deviation towards smaller Stokes numbers 

will occur. However, large Reynolds numbers should generally be avoided to prevent particle 

blowoff from the impact plate because of the high gas velocities. 

Deviations towards larger Stokes numbers, which have also been observed in experiments, 

occur with Reynolds numbers of less than 100. 

For details see Table 1-3 at the end of this description. 

2 Mode of Operation and Structural Components 

2.1 Mode of Operation 

A dust-Iaden gas flows through an extraction probe and a transition cone into the impactor 

where the dust particles are segregated according to their size and collected in the individual 

impactor stages. The dust particles which are not collected in the impactor stages are retained 

in a backup filter (see Figs. 1). 

To obtain sufficiency of dust, an adequate volume flow has to be passed through the impactor. 

Therefore in consideration to the specified Reynolds number range, several identical 

nozzles are arranged in parallel in an impactor stage (multi-nozzle impactor). 

As far as the volume flow is concerned, an impactor, must be operated in the defined limits, 

in accordance with its design and the calculated flow (see excel file). Moreover, the requirement 

of isokinetic sample gas extraction has to be met. Losses due to deposits of particles 

on surfaces different than the impact plates of the individual Impactor stages is well as losses 

due to particle bouncing and blowoff from the impact plates limited the use of the impactor 

(see table 1).

2.2 Components 


The cascade impactor consists of the following components which is manufactured from corrosion-proof 

titanium materials: 

Extraction Probe 

For adapting the gas velocity at the extraction probe inlet to the gas velocities prevailing in 

the waste gas duct, a set of exchangeable probes with different diameters is required. 

Transition Cone 

This part is required to provide a transition between the diameter of the extraction probe and 

the diameter of the first nozzle plate. 

Impactor Casing 

This casing is required for the accommodation of the impactor inserts which consist of the 

individual impactor stages, the sealing elements and the backup filter. 

Impactor Stages 

These consist of the nozzle plates and the impact plates (filter holder). 

The impact plates are arranged rectangularity to the direction of flow. 

The impact plates are either covered by suitable Munktell quartz fibre filter (collecting plates) 

or provided with a coating (adhesive agent), depending on the properties of the particles to 

be studied, on the gas composition, the gas temperature and the requirements of the subsequent 

analysis. 

Backup Filter 

This alter follows immediately after the last impactor stage and is to collect the particles that 

have not been retained in the impactor stages. Suspensions filters of the S category are 

used for this purpose (Munktell-filter). 

3 Measuring Arrangement 

The Arrangement of the measuring equipment must comply with the requirements of the application. 

The following contains a description of a typical installation for a measurement by 

impactor in accordance with Guideline VDI 2066 Part 1. 

3.1.1 Sampling Equipment 

All gas carrying parts are of corrosion-proof titanium 

Extraction Probes effective diameter 3 to approximately 16 mm, straight probe design. 

Cascade Impactor consisting of impactor casing and impactor insert, selection in accordance 

with the application.


3.1.2 Equipment for Sucking, Adjusting and Measuring the Sample Volume Flow Rate 

Gas Drying Column Silica gel packed, minimum column diameter 70 mm, height of the 

packing approximately 300 mm. 

Condensate Trap if necessary, the drying column is preceded by a gas cooler. 

Suction Equipment e.g. corrosion-proof pump; volume flow rate approximately 4 m³/h at 

400 mbar on the intake side. 

Suction Tube inside diameter approximately 8 mm, outside diameter for lengths of 

more than 2 m at least 20 mm; in order to prevent the condensate 

from flowing back into the cascade impactor, it may either be necessary 

to provide a heating system for the suction tube or to install a 

condensate trap. 

Gas Volume Meter gas volume meter for measuring the passed gas volume; nominal 

capacity 6 m³/h, calibration tolerance 2%, permissible depression with 

reference to the atmosphere 200 mbar. 

Rotameter for monitoring the sample volume flow rate. 

alternatively: 

Gas Volume Meter gas throttle device (orifice or nozzle), design and use in accordance 

with DIN 1952 or Guideline VDI/ VDE 2040 Part 2. 

Temperature Measuring Devices for measuring the gas temperature at the gas volume meter 

and the tapping point. 

Differential Pressure Measuring Device e.g. U-tube manometer for measuring the differential 

pressure in the gas volume meter and in the waste gas duct 

with reference to the atmospheric air pressure. 

Time Measuring Device for measuring the sampling period. 

Barometer for measuring the atmospheric air pressure at the sampling point. 

Shutt off Valves and Control Valves for coarse and fine adjustment of the sample gas flow 

rate. 

Junction Tubings the junction tubing’s between the individual equipment parts must be 

corrosion-proof, flexible and heatable, if necessary. 

3.1.3 Equipment for Measuring the Gas Velocity and the Gas Composition 

Gas Velocity Measuring Device Prandtl tube in combination with a micromanometer. 

Gas Analysers (if necessary) for determining the main components of the waste gas at 

the tapping point in connection with the determination of 

the gas density and viscosity; e.g. CO2,O2, H2O depending 

on the application.


3.1.4 Accessories for the Pretreatment and Posttreatment of the Collecting Plates in 

the Laboratory 

Scales minimum resolution 0.1 mg; installation, if possible, in a room with 

constant temperature and humidity (recommended values: temperature 

approximately 20°C, constant relative humidity within the range 

of 50 to 60%). 

Drying Chamber for heating up the collecting plates to approximately 250°C 

Furnace only necessary if temperatures above 250°C are required. 

Desiccator for equilibrating the samples. 

Scale pans for accommodating the collecting plates made, for instance, of Aluminium 

foil. 

Transport Container for the accommodation of the impactor inserts or impactor stages. 

3.1.5 Working Materials 

Collecting Plates can used with Munktell quartz-fibre filter. Stamps accessories, for the 

hole in the middle is in the delivery capacity. 

Backup Filter for the collection of particles that have not been retained in the impactor 

stages, e.g. quartz fibre filter of the S category (Munktell). 

Adhesive Agent for improving the adhesion of the dust particles: high-vacuum grease 

Apiezon L or Apiezon H. 

Drying Agent silica gel with colour indicator. 

3.2 Measuring Setup 

As far as the connection to the supply system and the equipment of the measuring site are 

concerned, reference is made to Guideline VDI 2066 Part 1. The sampling ports should be 

adequately dimensioned in accordance with the impactor type and the wall thickness of the 

waste gas duct. 

The cascade impactor has to be equipped with a straight inlet probe (acc. to VDI 2066, 

page 7) and to be installed in the waste gas duct so that it will face the gas stream. 

When arranging the suction equipment after the gas volume meter, the volume flow can be 

controlled by adding ambient air. By adding ambient air, the test gas can be cooled in the 

condensate chamber at the same time. 

Unlike the measuring setup it may be necessary under special circumstances, such as in 

oversaturated waste gases, to locate the cascade impactor outside the waste gas duct. For 

this purpose the impactor is headed by a suction tube, an elbow and an extraction probe. 

These have to be heated up, if necessary. With this arrangement, particles may get deposited 

on the walls of the extraction system thus affecting the fractionating separation in the 

impactor.

4 Preparation and Performance of the Measurement 


4.1 Selection and Pretreatment of the Collecting Plates and the Backup Filter 

A suitable set of collecting plates and backup filters have to be chosen and pretreated for 

each measurement. 

The collecting plates (filter holder) and the backup Filter is in titanium, so that is inert in respect 

of the constituents of the sample gas stream so as to avoid changes in the mass 

caused by chemical reactions. Titanium collecting plates which have been pretreated with 

Munktell quartz fibre filter have proven successful in practice for many applications. It is advisable 

to check the materials considered adequate in a preliminary test for changes in mass 

and thus to ensure that the material most suitable for the purpose will be selected. 

To avoid weight losses, the filter of the collecting plates and the backup filter, both made of 

quartz fibre, are each accommodated in filter holder and placed in the drying chamber where 

they are left for at least 1 hour to dry at a temperature of 180°C. If the cascade impactor is to 

be used at temperatures above 180°C, care should be taken to subject the collecting plates 

and the backup filter to a pre- and posttreatment at a reasonably higher temperature in order 

to avoid losses of binding agent etc. during the measurement. After the heat treatment, the 

filter holder containing the collecting filters and the backup filter have to be cooled in the desiccator 

for at least 1 hour before weighing. After weighing they have to be kept in Petri 

dishes, well protected from dust. 

The introduction of the weighed collecting filter holder into the prepared impactor inserts 

should preferably be done in the laboratory, since adequate rooms for this sort of work are 

very often not available on the site where the measurements have to be carried out. The 

number of measurements to be made should not exceeds the number of available impactor 

filter holder. The filter holder with the filter can easy exchanged in situ. Utmost caution is advised 

for the transport of the prepared filter holder and backup Filters to the site and of the 

dust-laden plates and backup filters back to the laboratory. 

The individual collecting filter holder and backup filter holder must allow easy identification. 

Since they themselves must not be marked (change in weight!), it is advisable to mark the 

pans with the set and the stage numbers. The right order should be strictly adhered on insertion 

and withdrawal. 

4.2 Pretreatment of the lmpactor Inserts 

The individual components of the impactor insert have to be cleaned in the ultrasonic bath 

before each measurement. Normal tap water to which some detergent or alcohol has been 

added is generally sufficient as cleaning agent. When tap water is used carefully rinsing with 

distilled water is necessary to avoid calcareous deposits. 

After drying, the nozzle plates, collecting plates (filter holder) and gaskets have to be 

checked for appreciable damage. Care should be taken during the assembly to prevent the 

gaskets, collecting plates and backup filter from being damaged. 

4.3 Performance of the Measurement 

4.3.1 Measurement Planning 

Before carrying out, the measurement should be thoroughly planned in accordance with 

Guideline VDI 2066 Part 1. This includes the determination of the number and the location of 

the sampling points. Unlike the tubular filter device, which is used for measuring the total


dust content, the impactor does not permit free selection of the gas flow rate once the probe 

diameter has been established. On the contrary, the gas flow must be kept constant during 

the measurement (sampling). This means that one measurement can only cover sampling 

points of approximately identical gas velocity (deviations of +30% are permissible) and that 

grid measurements require several measuring operations if there are significant differences 

in the velocity distribution. 

To calculate the gas flow rate use the excel file, which is in the delivery capacity. Set in all 

necessary data of the duct and gas specification and see the proposed nozzle diameter. If 

the Reynold Number between 100 and 3000 the theory of the impaction is valid and the plates 

contents the particle according to the shown cut offs. 

If the proportion of particles having a diameter of more than 10 µm is expected to exceed 

approximately 15% (by mass), it is necessary to reduce the sampling period, to prevent an 

overload of the first stage. Waste gas dust contents of more than 100 mg/m³ are indicative of 

a considerable proportion of particles having a diameter of more than 10 µm. 

4.3.2 Waste Gas Data 

To permit the adjustment of approximately isokinetic sucking conditions it is necessary to 

determine the waste gas velocity at the established sampling points. 

The differential pressure may, for instance, be measured with a Prandtl tube in combination 

with a micromanometer from the company Paul Gothe (see: www.paulgothe.de). The density 

has to be calculated from the pressure, temperature, gas composition and the molar masses 

of the gas components. 

For the evaluation of the results of the impactor measurements it is necessary to know the 

viscosity of the waste gas. Frequently the viscosity of the air at the corresponding temperature 

of the gas can be used in the calculation because the major part of the waste gases 

consists in nitrogen and oxygen. 

To calculate the flow rate through the impactor use the excel file. Have a look at the Reynold 

number, shown in the excel-file. 

4.3.3 Handling the Cascade Impactor during Operation 

Dust measuring by means of an impactor is done in a similar way to dust measuring by 

means of a tubular filter device. The individual working steps are described below. 

When introducing the impactor sampling system into the waste gas duct, care should be 

taken that the dust adhering to the walls of the duct or deposited in the duct does not enter 

the probe. Moreover, any flow through the impactor caused by the difference between duct 

and ambient pressure must be avoided. The shut-off valve has to be kept tightly closed for 

this purpose until after the start-up of the sucking system. 

It is advisable, particularly for measurements in the waste gas having a temperature which is 

only slightly above the dew point, to preheat the sampling system so as to ensure that the 

temperature in the impactor does not drop below the dew point temperature. Preheating can 

in general be carried out outside the duct, in a furnace, or by keeping the impactor for a sufficiently 

long period in the waste gas stream before performing the measurement. The opening 

of the probe must be adjusted in the direction of the gas flow to prevent particles from 

entering the impactor before the measurement starts.


During the sucking procedure (sampling period), the opening of the probe at the individual 

sampling points has to face the gas flow. 

The sampling period of the impactor should be chosen to ensure collection of a sufficient 

mass of dust per impactor stage to permit weighing with sufficient accuracy and to prevent 

overloading of the stages. 

After each measurement or when moving the sampling system to another sampling point, the 

shut-off valve has to be closed before the suction unit is switched off in order to avoid reverse 

flow through the impactor. Then the probe has to be aligned with the direction of the 

gas now and removed from the duct. The impactor or the impactor insert respectively is kept 

away from the measuring system and stored in a dust free atmosphere until evaluation. Drying 

and re-weighing of the collecting plates and the backup Filter is done under the same 

conditions as the determination of the mass of the unloaded components. The drying temperature 

of the loaded collecting plates and the backup filter can be limited due to possible 

changes of the collected dust. 

Deposits of dust in the sampling train have to be extracted and considered for the evaluation. 

The collecting filter holder of the individual impactor stages and the backup filter holder 

should be checked again before and after re-weighing in order to prevent measuring or interpretation 

errors: 

- A change in the colour of the backup Filter may be due to condensate having flown back 

to the backup filter either during sampling or immediately afterwards or due to the temperature 

in the impactor having dropped below the dew point during the measurement. 

This lets the particle size distribution in the result appear to have been shifted towards 

smaller particle diameters. 

- If dust deposits are not clearly delimited on the collecting plates, the respective collecting 

plate may have been overloaded. This may result in a shifting of the particle size distribution. 

An Figure in the chapter: “hints during sampling” shown collected dust at the different 

collecting plates. 

If the particle size distribution is unknown, the decision whether the impactor can used or not 

can be taken after the first measurement. The decision can be taken on visual assessment of 

the collecting plates. 

4.3.5 Treatment of the lmpactor Inserts 

The impactor inserts have to be handled with utmost care. Containers with compartments for 

the individual accommodation of several impactor inserts have proven successful for transport. 

Since the nozzle plates are not firmly installed, the containers should be transported in 

a vertical position. They must not be tilted nor exposed to vibration or shocks. Installation and 

dismantling of impactor inserts has to he carried out at a location without draught. It has to be 

ensured that the collecting plates and the backup filters do not get damaged or contaminated. 

If no laboratory is available at the measuring site, the used impactor inserts have to be returned 

with great caution to the laboratory.

4.3.6 Evaluation of the lmpactor lnserts in the Laboratory 


After sampling the collecting plates and backup Filters must again, as in the pretreatment 

procedure, be put individually into their respective marked pans, and placed in the drying 

chamber. Before weighing they have to be kept for 1 hour at a temperature of 180°C and 

cooled down in the desiccator. 

Loose dust lying on the plates of the individual stages of the impactor has to be included on 

weighing. If sufficient dust hits been collected in the impactor stages, a balance with a readout 

precision tolerance of 0.1 mg may be used. 

4.3.7 Evaluation of the first cone 

For evaluation of particle larger PM 10 it is necessary to determine the dust mass collected in 

the first cone (transition between sampling probe and first impactor stage) by differential 

weighing. A weighing accuracy of 0.1 mg should be aimed at. If differential weighing is not 

possible, the dust collected has to be transferred quantitatively from the cone to a weighing 

pan. If a dust of more than 20 mg has been collected in the cone, it will mostly be sufficient to 

transfer the dust from the cone to the weighing pan by means of a brush. 

If the dust mass is small, the cone has to he washed out. For this purpose the outside has 

first to thoroughly cleaned. If necessary, acetone has to be used to remove the grease from 

the threads of the lid. After this, the cone is washed out with approximately 50 ml of distilled 

water or methanol and rinsed with a further 25 ml of distilled water or methanol. 

The dust mass can be determined by filtering the suspension through a membrane filter having 

a pore size of approximately 1 to 2 µm. If the suspension contains soluble substances, it 

has to be evaporated for mass determination. 

4.3.8 Measurement of Gases with High Water Vapour Content 

If the waste gases contain a high proportion of water vapour, the determination of the gas 

flow rate through the cascade impactor may be affected by errors occurring on measuring 

the water vapour content. If the gas volume is measured by means of a volume meter which 

is headed by a drying column, exact measurement of the water dew point is necessary to 

minimise the error occurring on dry to moist gas volume conversion, this is particularly important 

with water dew points of more than 80°C. 

If the waste gas temperature is only slightly above or equal to the dew point temperature, the 

cascade impactor has to be heated up in the heater for the cascade impactor to a temperature 

approximately 50°C above that of the waste gas before installation into the waste gas 

duct. After installation the cascade impactor needs time to adapt the temperature to that of 

the waste gas. Normally this will take about 15 minutes. In this way condensation is prevented 

in the cascade impactor. 

By using a heated gas throttle device in combination with a heated suction tube, it is possible 

to measure the volume flow rate through the cascade impactor including the water vapour 

content directly. 

For oversaturated waste gases containing droplets it is normally necessary to use heated 

sampling equipment with a cascade impactor installed outside of the waste gas duct. With 

this arrangement the droplets dry up forming nuclei of dissolved and undissolved impurities 

which are separated as considerably smaller particles in the corresponding cascade impactor 

stage. Due to increased separation of coarse particles in the sampling train, the use of this 

arrangement is limited to particles having a diameter of less than 4 µm.

4.3.9 Selection of Suitable Sampling Probes 


The volume flow rate of a cascade impactor can not be selected freely. It does, however, 

influence the location of the particle size cut of the individual impactor stages. Therefore, the 

impactor must be operated with from the excel file calculated constant volume flow rate during 

measurement. To achieve an approximately isokinetic sample gas stream it is necessary 

to have a set of suitable sampling probes. The appropriate probe diameter is determined by 

the Excel-file as a function of the required sample volume flow rate and of the waste gas velocity, 

in accordance with the following equation: 

4 •V 

d = 

π • w 

d = diameter of the sampling probe in m 

V = sample volume flow rate at operating conditions in m³/s 

W = waste gas velocity in m/s. 

From the set of available sampling probes the one with the cross-sectional area coming most 

closely to the dimensions of the calculated probe should be chosen. 

It is advisable to use the next smaller size of probe in order to have an increasing of the gas 

volume flow at the nozzle. This give less errors. In practice, probes with cross-sectional areas 

derated by the factor 1 have shown good results the volume flow rates. The probe diameter 

should, however, not be smaller than 3 mm. 

Straight and curved probes are available for the Johnas cascade impactor, the latter under 

the name of "gooseneck probes". Due to increased coarse particle separation in a curved 

probe, this type of probe should only be used for particles with diameters of less than 4 µm. 

4.3.10 Calculating the Sample Volume Flow Rate 

Use the excel-file to calculate the sample flow rate. 

It has to be corrected according to the gas conditions in the gas volume meter by the following 

equation: 

TZ 

• Pm 

Vz 

= Vm 

• • S 

Tm 

• PZ 

Vz = volume flow rate in the gas volume meter m³/s 

Vm = sample volume flow rate at operating conditions in m³/s 

Tz = temperature of the gas in the gas volume meter in K 

Tm = temperature of the gas at the measuring point (waste gas duct) in K 

Pz = absolute pressure in the gas volume meter in bar 

Pm = absolute pressure at the measuring point (waste gas duct) in bar 

S = dry to humid gas volume ratio 

At the beginning Tz and Pz are unknown. Estimated values have to be used in the calculation 

to achieve a first approximation. Or the basis of these estimated values, the volume flow rate 

of the impactor is first of all adjusted. After a sufficient long measuring period the values obtained 

at the beginning of the measurement may be used for further correction. 

With short measuring periods it is advisable to stick to the gas volume meter setting based 

on the estimated temperature and pressure values, otherwise the adjusting of the volume 

flow rate will take up to large a proportion of the measuring period.


The volume flow rate V, can be checked by means of a variable area flowmeter. 

4.3.11 Estimating the Measuring Period 

The measuring period may be estimated from the desired impactor load and the dust content 

of the waste gas in accordance with the following equation: 

T = 

q 

f 

m 

•V 

m 

= 

q 

tr 

m 

•V 

Z 

T = measuring period in s 

M = desired impactor load in mg 

Vm = sample volume flow rate under operating conditions in m³/s 

VZ = volume flow rate through the gas volume meter in m³/s 

qf = dust mass concentration in the waste gas related to the operating conditions in mg/m³ 

qtr = dust mass concentration in the dry gas, related to the condition at ambient temperature 

and ambient pressure in mg/m³. 

The load capacity of the cascade impactor depends on the particle size distribution. The 

measuring periods for narrow particle size distributions may be considerably shorter due to 

possible overcharging of individual stages. If necessary, that is, for instance, if the dust content 

is unknown, the measuring period has to be estimated by a visual assessment of the 

dust-Iaden collecting plates after the first use. This requires some experience. It is more advisable 

to evaluate the first measurement exactly to allow purposeful application of the impactor 

for further measurements. 

5 Evaluation of the Measured Data and Calculation 

5.1 General 

The mass of the dust which has been impacted on the individual collecting plates of the impactor 

and which is determined by weighing is the direct result of the impactor measurement. 

At the first collecting stage –PM10 filter holder- are collected particle with dae50 value greater 

than 10µm. The summary mass of the second preceding stage –PM 2.5 filter holder- and the 

backup filter enclosed 50 % of particle with dae50 value smaller as 10µm, named PM 10. The 

mass of the backup filter enclosed 50 % of particle with dae50 value smaller as 2.5 µm, named 

PM 2.5. 

The cut-off curve is shown in figure 2-3. 

The mass of the second impactor stage –PM 2.5 filter holder- collected defined particle size 

intervals between PM 10 and PM 2.5. The actual cut off can read out from the excel file.

6 Performance Characteristics and Application 


The performance characteristics mentioned below were determined for the johnas round 

nozzle impactors, if the following minimum requirements are met: 

- ratio S/D > 1.5 

- ratio L/D> 0.25 

- number of nozzles per stage: the Reynolds numbers for the flow in the nozzle jets must 

be within the range of 100 < Re < 3000. The Excel-file calculate the Reynold numbers. 

Therefore the operator can easy controlled the operating conditions. 

- collecting plate material: quartz fibre material with adequate adhesion properties to retain 

particles 

- suitable design to minimise "wall losses" 

6.1 Particle Size Range 

The median value of the aerodynamic diameter of the last stage of the impactor is about 2.5 

µm. The impactor is followed by an S-class backup filter which is characterised by its high 

collection efficiency for particles of less than 1 µm. In this way almost all the particulate matter 

is collected in an impactor. 

For larger particle sizes the application of the impactor is limited because of an increasing 

error rate in the case of 

- non-isokinetic sampling 

- deposits on surfaces which are not included in the evaluation, particularly in the inlet 

cone (transition between sampling probe and first impactor stage) 

- insufficient adhesion to the collecting plates causing particle bouncing or blowoff. 

The impactor Johnas is calibrated with monodisperse aerosols. For an accuracy required in 

practice it has been found that the mass fraction of the particles larger than 10 µm must not 

exceed 15%. 

If the proportion of particles larger than 10 µm exceeds the above percentage, it is advisable 

to use the impactor only for a short period so that bouncing particles of the first page will not 

get into the second and last stage. 

6.2 Impactor Load 

High Impactor loads permit, in general, better evaluation by reducing the influence of weighing 

errors. The range of 4 to 10 mg per stage should be aimed. 

If the chemical composition of the dust is known, low impactor loads will suffice provided a 

volumetric analysis procedure of adequate accuracy is applied. Table 1 shown the operating 

conditions. The Johnas can used also by high dust load over 100 mg/m³. An higher dust load 

does not restrict the application of the impactor. The first stage may be checked. For the interpretation 

of PM 10 and PM 2.5 is not the weighing of the first stage necessary.

6.3 Dust Content 


The limits of the waste gas dust content between which an impactor can be used are given 

by the load capacity and the requirement of a reasonable measuring period. In addition, the 

particle size distribution may have influence on the permissible limits of the waste gas dust 

content. 

The Johnas cascade impactors is special developed for low dust range and can be used 

within the dust content range up to 100 mg/m³ (see Table 1). Higher dust load can measured 

too, but the stages must controlled very well whether the high dust load happened influence 

of the impaction. The measuring period must set shorter, down to a period of about 3 minutes. 

Measurements of considerably lower duration should be avoided since the adjustment 

of the volume flow rate would take up to large a proportion of the measuring period. 

To achieve the optimum impactor load when handling gases with a dust content of about 1 

mg/m³, the measurement must last 5 h. However, useful results can already be obtained with 

loads of 10 mg and measuring periods of 30 min. 

6.4 Temperature Range 

The Johnas cascade impactors are available for waste gas temperatures of up to 400°C. In 

addition to the permissible maximum working temperature, the temperature resistance of the 

collecting plate material has to be taken into account. Glass fibre papers loose some of the 

binding agent at high temperatures which results in a loss in strength. Their suitability for 

application above 300°C must therefore be tested. The Munktell-quartz fibre filter can used 

up to 900°C. In this case, it is very important to pre-heat the Munktell-quartz fibre filter! 

6.5 Waste Gas Velocity 

The range of the velocities prevailing in waste gas ducts where cascade impactors can be 

used is limited by the volume flow rate of the cascade impactor and by the probe diameter. 

6.6 Reproducibility and Uncertainty 

The reliability of the measuring method can be assessed by the reproducibility’s and uncertainties 

of the undersize total. 

7 Possible Errors and Error Assessment 

When carrying out the measurements with the measuring equipment, errors may occur, 

which will affect the calculation of the median value of the aerodynamic diameter and the 

determination of the undersize total to a different degree. For the following error assessment 

it is understood that the impactor-specific parameters (dimensions and number of nozzles of 

the individual impactor stages and Stokes number) are known to a sufficient degree of accuracy 

and that they do not vary during the measurement. 

The measuring errors and their influences on the performance characteristics can be estimated 

as follows: 

a) Dust masses on the individual impactor stages and on the backup filter, if any errors on 

dust mass determination may be brought about by: 

- Improper handling of the impactor (condensate formation due to the temperature drop 

below the dew point, mechanical damage of the collecting plates, displacement of impacted


particles due to overloading of individual impactor stages, insufficient adhesion of the particles 

due to the use of unsuitable collecting plates 

- Influences of the waste gas on the collecting plates (mass increase or decrease due 

to sorption and chemical reaction of the plate material with the individual components of the 

waste gas 

- Thermal instability of the collecting plates (loss of binding agent, insufficient conditioning, 

wrong heating temperature and heating period 

- Weighing errors (limited read-out accuracy of the balance used) 

When handling the impactor properly and selecting the right collecting plates in accordance 

with the instructions given in this specification, the error rate for the determination of the 

mass of the individual impactor stages and the backup filter, if any, can be limited to + 0.5 

mg. This subjects the undersize total and the oversize total to an error of approximately ± 3 

%. 

b) Waste gas composition 

Errors in the determination of the waste gas composition affect the calculation of the gas viscosity 

and the conversion of the volume of the dry gas (determined by means of a volume 

meter) to the corresponding humid gas volume at operating conditions. If the volume fraction 

of the individual constituents is determined with a relative error of less than 5%, the influence 

on the gas viscosity will be negligible. 

If the proportion of water vapour in the waste gas is less than 50%, it can be determined with 

a relative error of +2%. This results in a relative error of + 1% for the determination of the gas 

volume passing through the impactor. With higher water vapour proportions the volume 

should be determined by means of a meter run with a gas throttle device. 

c) Temperature of the waste gas relative error of approximately ± 0.5% 

d) waste gas pressures 

static pressure: relative error of approximately ± 0.2% 

dynamic pressure: relative error of approximately ± 10%, 

e) Sample gas volume flow rate – measured by means of a gas volume meter 

relative error of approximately ± 2% 

f) Temperature of the sample gas volume meter flow rate in the gas volume meter and at 

the gas throttle device 

relative error of approximately ± 0,5% 

g) Pressure of the sample gas volume flow rate in the gas volume meter at the gas throttle 

device 

absolute pressure relative error of approximately ± 2% 

differential pressure relative error of approximately ± 2% 

h) Measuring period


Errors in the determination of the measuring period are normally negligible. With extremely 

short measuring periods (less than 3 min) a relative error of time of 5% has to be 

reckoned with because of the adjustment of the volume flow rate. 

8 Maintenance and Check of the Measuring Equipment 

8.1 Maintenance carried out at the Laboratory 

Each time the impactor has been used it should be carefully cleaned. This applies particularly 

to the threads of the impactor casing which has to be cleaned with a fine wire brash of 

brass. This will help to prevent the threads from getting jammed during operation due to contamination. 

The nozzle plates have to be cleaned in the ultrasonic bath and checked for damage by visual 

inspection each time they have been used. Periodical examination of the nozzle plates 

under the microscope is recommended. 

To prevent the measuring accuracy from being affected by corrosive waste gas components, 

the calibration of the gas volume meter or of the gas throttle device as well as of the temperature 

and pressure measuring instruments should be checked at pre-set time intervals. 

8.2 Checking of the Measuring Equipment before Use 

Care has to be taken when installing or replacing an impactor insert that the dirt deposited on 

the impactor components does not get onto the impactor insert. 

The complete measuring system has to be checked for leakage before starting the measurement. 

For this purpose the opening of the probe has to be closed with a stopper and a 

negative pressure of about 150 mbar to be produced in the measuring system. This is about 

three or four times the negative pressure expected during operation. If neither the variable 

area flowmeter nor the gas volume meter indicate a volume flow, the measuring system is 

regarded as non-leaking. 

The silica gel packing of the drying column has to be exchanged in due time (watch the colour 

of the indicator) and the condensate trap, if any, to be emptied. 

9 Applications 

The Johnas cascade impactors are well suited for determining the particle size PM 10 and 

PM 2.5 in flowing gases. They can be installed in any position, that is in vertical, inclined or 

horizontal waste gas ducts. 

10 Excel-file 

As explained above, the separation-diameters d(ae)50 of a Impactor dependent of the duct gas 

conditions. The cut off steps PM 10 and PM 2.5 is calculated for a quite certain operating 

condition (see table 1). So that these cut off diameter don't postpone themselves, if itself the 

duct gas conditions changed, e.g. temperature and pressure in the duct as well as water vapour 

and gas composition, the gas flow rate must set accordingly through the Impaktor. For 

the fast, exact calculation, the included Excel-file, in which the measured duct gas conditions 

are set in, calculate the gas flow rate. This gas flow rate must be used to guarantee the cut 

off diameters 10 µm and 2.5 µm.

Short instruction 


The impactor’s handling in principle works like the one of the plane filter heading device, just 

as the impactor is in principle operated with the same peripheral devices (sucking-in probe 

for isokinetic sampling as well as bent, nozzles, suction tubes, etc..). 

Cleaning 

The cleaning of the impactor is carried out like the one of the plane filter heading. 

Filters 

For the impactor’s operation Munktell quartz fibre filters MK 360, Ø 50 mm are designed. 

Back-up Filters 

The fully cured quartz fibre filter is inserted as usual into the filter holder (I) and fixed by the 

fixing ring (1). 

Filters of the PM 10 and PM 2.5-Stage 

The fully cured quartz fibre filters are punched out with the help of the provided tool into 

which the filter holders (D and G) are inserted and fixed with the fixing ring. 

Weighing 

If the filters’ weighing takes place before or after the sampling including the filter holders, 

measuring adulterations can be prevented which might, for example, occur through losses of 

dust mass due to the withdrawal of the filter from the filter holder. The weighing takes place 

after the acclimatisation of the filters under constant temperature and air humidity by a balance 

with a resolving power as high as possible. 

Assembly 

Assemble the individual parts (see figure 1) according to the described order. Employ seal Di 

14 under and Di 15 over the plane filter holder (see figure 6). These seals are highly important. 

Seal Di 45 is inserted above the first cone and seals the Cover upward. The thread can 

be sealed with a teflon tape when required. 

The seals are used according to figure 6. 

Cone (B) 

PM 10-nozzle plate (C) 

PM 10-impaction plate (E) 

with filter holder and fixing ring (D + d) 

PM 2.5-nozzle plate (F) 

PM 2.5-impaction plate (H) 

with filter holder and fixing ring (G + g) 

Back-up filter holder and fixing ring (I + i) 

Exit (J) 

Cover (K) 

Operation 

The included Excel program, into which the operational data such as the waste gas temperature 

and composition etc. are entered, determines the proper sucking-in probe for the isokinetic 

sampling. It also determines the flow rate with which the impactor is to be operated 

under the appropriate conditions.

Hints for the Sampling: 

Isokinetic suction: 


an equal suction rate will rarely be possible. Usually the nozzle diameter suggested by the 

Excel file will not be available. However, there should be available a nozzle set with 1 mm 

steps. The errors that occur with a high suction rate are smaller than those with too low a 

rate. The separation diameters depend on the rate inside the impactor. Therefore, the suction 

rate can be kept only through the selection of the nozzle. The rate inside the impactor 

must never be modified , including the suction rate. The nozzle with the second smaller diameter 

is selected, except the difference from the next bigger diameter is clearly smaller. 

Thus the rate at the nozzle point increases and effects a faster suction. The less the selected 

nozzle differs from the one prescribed by the Excel file, the more isokinetic requests are fulfilled. 

If the temperature or the pressure or generally the density of the gas changes, the rate 

inside the impactor must again be calculated. In this case the suction rate must also be modified. 

This process will always generate errors. The specialist on the spot must decide which error 

is of greater significance. With particles smaller than 5 µm derivations from isokinetics can be 

neglected. The position of the separation diameter is more important. In the case of modification 

of the density the rate inside the impactor should be adapted. This is the only way to 

make a statement at all. If the separation diameters shift too strongly, an analysis is impossible. 

VDI guideline 2066, part 10, delivers useful information that contributes to a decision. 

Analysis: 

All collecting plates can be used for the sampling. The total of the selecting plate PM 2.5 and 

the back-up filter is the so-called PM 10-fraction. The back-up filter contains the so-called PM 

2.5-fraction. 

If also those particles bigger than PM 10 are to be considered, the particles on the first filter 

plate and the deposits inside the cone are to be weighed out together. 

The single filter plates are conditioned and treated according to the measurement of VDI 

2066, part 10. 

Particles inside the Input Cone: 

With total dust measurements according to VDI 2066, sheet 7, there are usually no deposits 

that can be perceived inside the input cone of the filter heading device. The mass of the adherent 

particles is not important. This is clearly different when sampling with the GMU cascade 

impactor Johnas. The flow inside the input cone causes increased particle separation 

on the wall. If exclusively the PM 10- and PM 2,5-fractions are to be determined, the particles 

inside the cone can remain unconsidered as long as the deposits do not influence the flow 

inside the cone. In case of the development of deposits which reach far into the cone, also 

particles with a small aerodynamic diameter will stick to these deposits and thus will question 

the whole measurement. However, this will rarely be the case. Usually the cone will be covered 

with a thin dust layer. This dust layer contains only particles bigger than PM 10. 

If the fraction bigger than PM 10 is also to be determined, the particles adherent to the cone 

must be added to the filter of the first stage plate. Therefore, the cone is rinsed with alcohol 

and the suspension of alcohol and particles is filtered by a standard filter. Filtering can be 

accelerated via a nutsch with a vacuum. Subsequently, this filter is dried and treated in accordance 

with VDI 2066 part 10. 

Sampling Time: 

The sampling duration can deviate clearly from the half-hour sampling required according to 

the government laws. The necessary sampling time is limited by at least two factors. On the 

one hand, no filter should be overloaded. If considerable impaction ‘hills’ are developed on


the filter, also smaller particles are disturbed in their flight path and possibly separated on the 

wrong impact plate. This danger is given with particle distribution on one side. If this is unknown 

before the sampling, the sampling duration can be estimated only after regarding the 

individual impaction plates. The ‘hill’ should not be higher than the edge of the interior hole of 

the respective impaction plate. On the other hand, there is the danger that the step can not 

be analysed due to a lack of mass if there is too little dust mass on the filter. 

According to the investigations of the State Environment office Essen, the particles are 

clearly below 10 PM in filtered waste gas flows. The decrease of pressure behind the impactor 

is in this case the criterion for the first sampling time. Here the experiences of the total 

dust measurements according to VDI 2066, page 7, can be taken into account. Usually the 

back-up filter is sufficiently covered when the decrease of pressure above the filter is 200- 

300 mbar. Depending upon filter material and dampness the filter material can tear with 

higher vacuums and make the measurement useless. Please note: again the experiences of 

the specialists on the spot are more important than inflexible specifications. 

Area of Application: 

The area of application of the impactor is specified in figure 1. These boundary conditions 

guarantee that the calibration data also apply in modified situations. In order to make sure 

that the flow and the regularities are valid according to Marple’s theory, the Reynolds number 

must be between 100 and 3000. The medium free path of the gas should be within the scale 

for gases (~ 65 nm). Both quantities depend on the temperature, the pressure and the density 

of the gas. These data are calculated with the enclosed Excel file. 

From this results a clearly larger area of application of the impactor. Due to the titanium the 

temperature must not be more than 400°C. 

Gas with high Water Vapour Content: 

The titanium mass of the impactor is substantial. Therefore, the heating and the temperature 

adjustment of the impactor within the gas stream need much time. If the dew point is above 

the outside temperature, the impactor should be preheated. For the preheating the standard 

filter heater from the company Paul Gothe can used. Please note that not only the heating 

takes its time; so does the cooling if the impactor is brought in too hot. We recommend the 

Paul Gothe-temperature controller with PID-control. The temperature controller is characterised 

by a simple handling and can keep the impactor at a specified temperature very exactly 

when combined with the standard heater. 

Please note: The temperature of the impactor must not change during the sampling since 

otherwise the separation diameters shift. An impactor kept at a specified temperature is thus 

not only important by high water vapour. 

Horizontal Measurements: 

If the impactor is in a horizontal position in the flow during the measurement, there is a great 

torque at the suction pipe. A counterweight can be installed at the end of the suction pipe so 

that the holder of the suction pipe does not have to take up the entire torque (order no.: 

60.4). Besides, strengthened bent should be employed. 

Comparison with Total Dust Measurement (TSP): 

The dust quantity of all impact plates and the particles inside the input cone will not result in 

the mass of a total dust measurement according to VDI 2066, page 7. Wall losses cannot be 

avoided. These wall losses occur with each impactor. The GMU-impactor Johnas has only 

small wall losses because of the optimised flow guidance. Nevertheless, results reduced to 

up to 20% can occur. The results of the impactor measurements are not suitable for the calculation 

of the total dust measurement. According to investigations by the Gerhard Mercator


University, Duisburg, the losses predominantly occur with particles bigger than PM 10. The 

mass of the PM 2.5- and PM 10-fractions can thus be regarded as absolute. 

Artifact Formation: 

Impactors separate particles according to their aerodynamic diameter. This aerodynamic 

diameter is a function of many parameters. The mass of the particle is only one parameter. If 

the mass changes, the aerodynamic diameter changes with it although the radius does not 

have to change obligatorily. Hygroscopic salt mixtures will therefore indicate different aerodynamic 

diameters, depending upon the air humidity. Semivolatile substances will indicate a 

greater mass during the sampling than after the measurement. The analysis does not only 

have to determine the total mass, but also the ingredients. Possibly the deliquescence point 

can be calculated from the composition of the elements (cations and anions). Thus the mass 

modifications by water content or reduced results through semivolatile substances can be 

measured. They are to be taken into account when interpreting the results. 

OUT STACK-Measurements: 

The impactor should generally be placed In-Stack directly behind the nozzle. If this is not 

possible, goose-neck nozzles can be used or the impactor is installed behind the bent or behind 

the suction tube. No matter where you place the impactor: The sections in front of the 

impactor are separating devices of unknown kind. Only a very limited analysis is possible. 

This also applies for other impactors, even if the manufacturer offers suitable accessories. 

Physics is not a function of marketing. 

Comparison with other Impactors: 

We do not shy away from a comparison of Johnas with other impactors, but you can hardly 

compare pears to apples. A multi-step impactor does not record the PM 10 or PM 2.5fraction 

specifically. Not only is the calculation of the PM 10 and PM 2.5 mass based on the 

steps highly complex, but also is this method afflicted with many possible errors. Deviations 

are not rarely a cause of false calculation data. In case of doubt those results obtained by a 

simple weighing by the GMU-impactor Johnas are more reliable. Cascade cyclones are socalled 

3-D-separators and only applicable to the status calibrated in each case. 

Fun: 

That’s our wish for you, 

although we know that 

measurements of PM 10 

and PM 2.5 are very complex !! 

Example for dust on filter : 

1: PM-10-stage 

2: PM-2,5-stage 

3: Back-Up-filter

Table 1: Condition for the Impactor 


Mittel min max 

Konzentration [mg/Nm³] 10 1 100 

Temperatur [°C] 135 20 250 

Druck [mbar] 1000 850 1100 

Feuchte [g/Nm³] 30 0 100 

Gaszusammensetzung Luft 30% CO2 

Kaminöffnung Standard 3" 

Table 2: Results Cut-Off of the University Duisburg: 

Geometric Aerodynamic 

cut off 

diameter 

diameter 

Johnas 2 

PM 10-Stage 10,00 µm 10,25 µm 51,8 ± 6,5 % 

PM 2,5-Stage 2,495 µm 2,56 µm 49,4 ± 2,1 % 

Table 3: Calibration Results of the University Duisburg of the effective Cut-Offs (d(ae)50): 

d(ae)50 deviation acceptance 

US-EPA 

PM 2,5-Stage 2,53 µm + 1,2 % ± 8 % 

PM 10-Stage 9,95 µm - 0,5 % ± 5 %

Figure 1: GMU - Impactor johnas 

Johnas II page 23

separation [%] 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 


0 

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 

d(ae) [µm] 

grease PM Filter PM US WINS 

Figure 2: effective particulate matter of the stage 2.5 µm- GMU - Impactors johnas, In the 

comparison with the US WINS PM 2.5-Impactor (calculated from "penetration efficiency 

curve") 

separation [%] 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 

d(ae) [µm] 

grease PM 10 Filter PM 10 thorax US PM 10-Inlet 

Figure 3: effective particulate matter of the stage 10 µm- GMU - Impactors johnas, In the 

comparison with the US PM 10-Inlets (calculated from "effectiveness curve") and 

the thorax fraction

62,4 

Wall losses 

not consider 

37,6 

Figure 4: Mass of Al2O3- test dust on the impaction stages, 


Figure 5: Wall losses on the impact stages PM 10 and PM 2.5 in mass percent calculated to 

the total mass of each stage 

Picture 1: GMU - Impactors johnas 

62,7 

10 µm - 2.5 < 2.5 

96,4 % 98,3 % 

3,6 % 

10 µm - 2.5 < 2.5 

Filter Wall losses 

1,7 % 

Wall losses 

consider 

37,3

Figure 6: Seals 

Johnas II page 26

Attention – In case of using the excel-file, this following license agreement will be accepted by the user! 

Achtung – Wird die Excel-Datei verwendet, akzeptiert der Benutzer diese folgende Lizenz-Vereinbarung! 

Excel-Berechnungsdatei für den Kaskadenimpaktor Johnas 

Die auf dem Datenträger enthaltene Excel-Datei fällt unter den Schutz des Urheberrechtsgesetzes. Alle 

Urhebernutzungsrechte und andere geistigen Eigentumsrechte in Bezug auf die Datei verbleiben dem Programmautor 

und dem Lizenzgeber. Der Anwender erhält eine beschränkte, nicht ausschließliche und widerrufliche Lizenz zur 

Verwendung der Datei. Der Anwender verpflichtet sich, die Datei weder zu irgendwelchen Zwecken an andere 

Benutzer zu verleihen, zu vermieten, zu leasen oder zu unterlizensieren. 

Der Anwender verpflichtet sich, die Datei in angemessener Weise vor unbefugter Benutzung, Modifizierung, 

Vervielfältigung, Verteilung und Veröffentlichung zu schützen. Der Anwender erhält das Recht, zu Sicherheitszwecken 

eine Kopie der Datei anfertigen zu können. Für Verwendungen und Kopien der Datei zu anderen als in der Richtlinie 

angegebenen Belangen besteht keine Befugnis. Unverzüglich nach Erhalt des beiliegenden Datenträgers erfolgt eine 

Abnahmeprüfung durch den Anwender. Hierbei eventuell festgestellte Fehler wird der Lizenzgeber innerhalb von 

vierzehn Tagen beseitigen oder Ersatz liefern. Jede weitere Gewährleistung wird ausgeschlossen. Die hinter der 

Datei stehenden Modelle oder Modellvorstellungen stellen den Stand der Technik zur Zeit der Entwicklung der Datei 

dar. Für die Richtigkeit der Formeln, Modelle und/oder Programme wird keine Gewähr übernommen. Garantien 

bezüglich der Nutzung und Eignung der Datei für einen bestimmten Zweck werden nicht gegeben. In allen Fällen ist 

die Haftung auf den Datenträgerpreis begrenzt. 

Die auf dem Datenträger enthaltene Dateiversion kann jederzeit vom Lizenzgeber für ungültig erklärt werden. Wird 

die Richtlinie VDI 2066 Blatt 10 zurückgezogen oder durch eine Neuausgabe ersetzt, so verliert auch die 

dazugehörige Datei ihre Gültigkeit. 

Paul Gothe, Bochum den 10.12.03 

Excel-calculation-file for the Cascade impaktor Johnas 

The Excel-file on the data disk falls under the protection of the copyright-law. All originator-usufructs and other mental 

titles in reference on the file remain by the program-author and the licensor. The user gets a limited, not exclusive and 

revocable license to the application of the file. The user commits himself neither to lend the file to any purposes to 

other users to rent to lease or to under-license. 

The user commits himself to protect the file in appropriate manner from unauthorised use, modification, duplication, 

distribution and publication. The user gets the right, to prepare a copy of the file for the security. Instantaneously after 

receipt of the enclosed data carrier, a decrease-examination takes place through the user. On this occasion possibly 

determined mistake will remove by the licensor within fourteen days or will deliver substitute. Each more guarantee is 

excluded. The models standing behind the calculation or model-ideas represent the stand of the technology at the 

time of the development of the file. For the correctness of the formulas, models and/or programs is taken on no 

assurance. Guarantees respecting the utilization and suitability of the file for a certain purpose are not given. In all 

cases, the liability is restricted on the data carrier-price. 

That on the data carrier existing file-version can be explained by the licensor for invalid at anytime. The guideline VDI 

2066 part 10 is withdrawn or is replaced with a reprint, so also the pertinent file loses their validity. 

Paul Gothe, Bochum the 2003-12-10,

Impactor Johnas - Paul Gothe GmbH

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?