Ambient air - Determination of the particle number concentration of atmospheric aerosol

This Technical Specification describes a standard method for determining the particle number concentration in ambient air in a range up to about 107 cm–3 for averaging times equal to or larger than 1 min. The standard method is based on a Condensation Particle Counter (CPC) operated in the counting mode and an appropriate dilution system for concentrations exceeding the counting mode range. It also defines the performance characteristics and the minimum requirements of the instruments to be used. The lower and upper sizes considered within this document are 7 nm and a few micrometres, respectively. This document describes sampling, operation, data processing and QA/QC procedures including calibration parameters.

Außenluft - Bestimmung der Partikelanzahlkonzentration des atmosphärischen Aerosols

Diese Technische Spezifikation stellt ein Standardverfahren zur Bestimmung der Partikelanzahl-konzentration in Außenluft im Bereich bis etwa 107 cm−3 für Mittelungszeiten von mindestens 1 min auf. Das Standardverfahren basiert auf einem im Zählmodus betriebenen Kondensationspartikelzähler (en: condensation particle counter, CPC), gegebenenfalls mit geeignetem Verdünnungssystem, falls die Konzentrationen den Bereich des Zählmodus überschreiten. Weiterhin werden Leistungskenngrößen und Mindestanforderungen für die zu verwendenden Geräte definiert. Der betrachtete Partikelgrößenbereich reicht von 7 nm bis zu einigen Mikrometern. Diese Technische Spezifikation beschreibt Probenahme, Betrieb des Geräts, Datenverarbeitung und QA/QC-Maßnahmen, einschließlich der Kalibrierparameter.

Air ambiant - Détermination de la concentration en nombre de particules de l'aérosol atmosphérique

La présente Spécification technique décrit une méthode normalisée de détermination de la concentration en nombre de particules dans l’air ambiant sur une plage allant jusqu’à environ 107 cm-3, pour des durées de calcul des moyennes supérieures ou égales à 1 min. La méthode normalisée repose sur un compteur de particules à noyaux de condensation (CPC) fonctionnant en mode comptage et sur un système de dilution approprié pour les concentrations excédant la plage du mode comptage. Elle définit également les caractéristiques de performance et les exigences minimales relatives aux instruments à utiliser. Les tailles de particules minimale et maximale considérées dans le présent document sont, respectivement, de 7 nm et quelques micromètres. Le présent document décrit le prélèvement, le fonctionnement, le traitement des données et les procédures d’assurance qualité et de contrôle qualité, y compris les paramètres d’étalonnage.

Zunanji zrak - Določevanje številčne koncentracije delcev atmosferskih aerosolov

Ta dokument opisuje standardno metodo za določevanje številčne koncentracije delcev v zunanjem zraku na območju do približno 10 na kvadrat 7 cm-3 za čase povprečenja, ki so dolgi največ 1 minuto. Standardna metoda temelji na kondenzacijskem števcu delcev (CPC), ki deluje v načinu štetja, in ustreznem sistemu redčenja za koncentracije, ki presegajo obseg načina štetja. Določa tudi lastnosti zmogljivosti in minimalne zahteve instrumentov, ki jih je treba uporabiti. Spodnje in zgornje velikosti, obravnavane tem dokumentu, so 7 nm in nekaj mikrometrov. Ta dokument opisuje vzorčenje, delovanje, obdelavo podatkov ter postopke zagotavljanja in nadzora kakovosti, vključno z umerjanjem.

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SLOVENSKI STANDARD
SIST-TS CEN/TS 16976:2017
01-julij-2017
=XQDQML]UDN'RORþHYDQMHãWHYLOþQHNRQFHQWUDFLMHGHOFHYDWPRVIHUVNLKDHURVRORY

Ambient air - Determination of the particle number concentration of atmospheric aerosol

Außenluft - Bestimmung der Partikelanzahlkonzentration des atmosphärischen Aerosols

Air ambiant - Détermination de la concentration en nombre de particules de l'aérosol

atmosphérique
Ta slovenski standard je istoveten z: CEN/TS 16976:2016
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
SIST-TS CEN/TS 16976:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS CEN/TS 16976:2017
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SIST-TS CEN/TS 16976:2017
CEN/TS 16976
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
August 2016
TECHNISCHE SPEZIFIKATION
ICS 13.040.20
English Version
Ambient air - Determination of the particle number
concentration of atmospheric aerosol
Air ambiant - Détermination de la concentration en Außenluft - Bestimmung der

nombre de particules de l'aérosol atmosphérique Partikelanzahlkonzentration des atmosphärischen

Aerosols

This Technical Specification (CEN/TS) was approved by CEN on 26 June 2016 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to

submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS

available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in

parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 16976:2016 E

worldwide for CEN national Members.
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Contents Page

European Foreword ...................................................................................................................................................... 5

Introduction .................................................................................................................................................................... 6

1 Scope .................................................................................................................................................................... 7

2 Normative references .................................................................................................................................... 7

3 Terms and definitions ................................................................................................................................... 7

4 Atmospheric aerosol ...................................................................................................................................... 8

5 Description of the method ........................................................................................................................... 9

5.1 Sampling and conditioning .......................................................................................................................... 9

5.1.1 Sampling ............................................................................................................................................................. 9

5.1.2 Drying ............................................................................................................................................................... 10

5.1.3 Dilution ............................................................................................................................................................ 11

5.2 Determination of the number concentration with a CPC .............................................................. 11

5.2.1 Condensation growth .................................................................................................................................. 11

5.2.2 Optical detection .......................................................................................................................................... 13

6 CPC performance criteria and test procedures ................................................................................. 14

6.1 General ............................................................................................................................................................. 14

6.2 General requirements of the CPC ........................................................................................................... 14

6.3 Test conditions .............................................................................................................................................. 15

6.4 Performance characteristics and criteria ........................................................................................... 15

6.5 Test procedures ............................................................................................................................................ 16

6.5.1 Inlet flow rate accuracy .............................................................................................................................. 16

6.5.2 Number concentration measurement range ...................................................................................... 16

6.5.3 Number concentration detection limit ................................................................................................. 16

6.5.4 Linearity and slope of response .............................................................................................................. 16

6.5.5 Detection efficiency curve at low particle size .................................................................................. 17

6.5.6 Upper particle size detection limit ........................................................................................................ 17

6.5.7 Zero count rate .............................................................................................................................................. 17

6.5.8 Response time ............................................................................................................................................... 17

6.5.9 Dependence of flow rate on supply voltage ........................................................................................ 17

6.5.10 Accuracy of temperature and pressure sensor calibration .......................................................... 18

6.5.11 Effect of failure of mains voltage ............................................................................................................ 18

7 Performance criteria and test procedures for the sampling and conditioning system ...... 18

7.1 General requirements ................................................................................................................................ 18

7.2 Performance characteristics and criteria ........................................................................................... 18

7.3 Diffusion losses ............................................................................................................................................. 19

7.4 Relative humidity ......................................................................................................................................... 19

7.5 Dilution factor ............................................................................................................................................... 19

7.6 Primary sampling flow ............................................................................................................................... 19

8 Measurement procedure ........................................................................................................................... 20

8.1 Measurement planning .............................................................................................................................. 20

8.2 Environmental operating conditions .................................................................................................... 20

8.3 Initial installation ........................................................................................................................................ 20

8.4 Initial checks on site.................................................................................................................................... 20

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8.5 Data processing and reporting ................................................................................................................ 21

9 Quality control, quality assurance and measurement uncertainty ............................................ 21

9.1 General.............................................................................................................................................................. 21

9.2 Frequency of calibrations, checks and maintenance ....................................................................... 21

9.2.1 General.............................................................................................................................................................. 21

9.2.2 Maintenance of CPC ...................................................................................................................................... 22

9.2.3 Calibration of CPC plateau region and linearity ................................................................................ 22

9.2.4 Determination of CPC low size cut-off ................................................................................................... 22

9.2.5 CPC zero check ............................................................................................................................................... 22

9.2.6 Number concentration check ................................................................................................................... 23

9.2.7 CPC flow rate calibration ............................................................................................................................ 23

9.2.8 Temperature and pressure sensor calibration .................................................................................. 23

9.2.9 CPC internal diagnostics ............................................................................................................................. 23

9.2.10 Sample system maintenance .................................................................................................................... 23

9.2.11 Relative humidity sensor ........................................................................................................................... 23

9.2.12 Dilution factor (where applicable) ......................................................................................................... 23

9.2.13 Leak check ....................................................................................................................................................... 23

9.3 Measurement uncertainty ......................................................................................................................... 24

9.3.1 General.............................................................................................................................................................. 24

9.3.2 CPC plateau detection efficiency ............................................................................................................. 24

9.3.3 CPC detection efficiency drift.................................................................................................................... 24

9.3.4 Flow determination ..................................................................................................................................... 25

9.3.5 Correction to standard temperature and pressure .......................................................................... 25

9.3.6 Sampling losses due to diffusion to walls ............................................................................................. 25

9.3.7 Dilution factor (where applicable) ......................................................................................................... 25

9.3.8 Calculation of overall uncertainty .......................................................................................................... 25

Annex A (normative) Determination of diffusion losses in sampling lines .......................................... 27

Annex B (informative) Example of the calculation of diffusion losses in a sampling system ........ 29

B.1 Description of the sampling system ....................................................................................................... 29

B.2 Air properties and diffusion coefficient ............................................................................................... 30

B.3 Losses in the primary sampling tube ..................................................................................................... 30

B.4 Losses in the secondary sampling tube and the dryer .................................................................... 31

B.5 Overall sampling losses .............................................................................................................................. 31

Annex C (informative) Data reporting ................................................................................................................ 32

C.1 Motivation ....................................................................................................................................................... 32

C.2 Level 0 (annotated raw data) ................................................................................................................... 32

C.3 Level 1 (data processed to final physical property, potential corrections applied, original

temporal resolution) ................................................................................................................................... 33

C.4 Level 2 (hourly averages, including measures of variability) ...................................................... 33

C.5 GAW WDCA Condensation Particle Counter Level 0 (raw data) file format example (system

without sample dilution): .......................................................................................................................... 35

C.6 Line-by-line explanations: ......................................................................................................................... 35

Annex D (informative) Uncertainty calculation (example) ........................................................................ 47

D.1 General.............................................................................................................................................................. 47

D.2 CPC plateau detection efficiency ............................................................................................................. 47

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D.3 CPC detection efficiency drift ................................................................................................................... 47

D.4 Flow determination ..................................................................................................................................... 47

D.5 Correction to standard temperature and pressure ......................................................................... 47

D.6 Sampling losses due to diffusion to walls ............................................................................................ 47

D.7 Dilution factor (where applicable) ........................................................................................................ 48

D.8 Calculation of overall uncertainty .......................................................................................................... 48

Annex E (informative) Atmospheric aerosols in Europe ............................................................................ 49

E.1 General ............................................................................................................................................................. 49

E.2 Mean concentrations .................................................................................................................................. 49

E.3 Examples of measurements...................................................................................................................... 50

Annex F (informative) Dilution systems ........................................................................................................... 53

F.1 Background .................................................................................................................................................... 53

F.2 Criteria for dilution systems .................................................................................................................... 53

F.3 Operation principles of dilution systems ............................................................................................ 53

F.3.1 General ............................................................................................................................................................. 53

F.3.2 Dilution systems with partial flow filtration ...................................................................................... 54

F.3.3 Dilution systems with external clean air supply .............................................................................. 54

Annex G (informative) Laminar flow.................................................................................................................. 56

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European Foreword

This document (CEN/TS 16976:2016) has been prepared by Technical Committee CEN/TC 264 “Air quality”,

the secretariat of which is held by DIN.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following

countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus,

Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,

Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

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Introduction

There is a growing awareness of the significance of aerosol particles with diameters of D < 1 µm for human

health as well as for their climatic impact. To assess air quality, it appears necessary to supplement

gravimetrically determined mass concentrations such as PM or PM with a measurement of the particle

10 2.5

number concentration. Since ultrafine particles with diameters of D < 0,1 µm make an almost insignificant

contribution to the mass of atmospheric aerosol particles, they can best be detected with counting measuring

methods of sufficient sensitivity.

As particle measurement instrumentation allows determining either the particle number concentration or the

particle number size distribution two Technical Specifications will be established:

— one dealing with the determination of the single parameter number concentration (a measure of “total”

number concentration),

— one dealing with the determination of number concentration within a limited number of size ranges.

Clauses 5 and 6 contain general information about the method and the expected properties of the aerosol to

be measured.

Clause 7 sets out the performance criteria for CPCs. Specifically, these are the relevant performance

characteristics of CPC instruments (without any sampling system), the respective criteria that shall be met,

and a description of how the tests shall be carried out. In general these tests are expected to be carried out by

test houses or CPC manufacturers rather than users, and could form the basis for type testing of CPCs in

future.

Clause 8 sets out the performance criteria and test procedures for the sampling and conditioning system (e.g.

dilution). These may be applied by manufacturers of sampling systems, test houses or users (network

operators).

Clause 9 sets out requirements for the installation, initial checks and calibrations, and operation of a CPC and

sampling system at a monitoring site, including routine maintenance, data processing (including use of QA/QC

data) and reporting. In general these will be the responsibility of users (network operators), though

calibrations requiring test aerosols shall only be carried out by suitably qualified laboratories.

Clause 10 sets out Quality Assurance and Quality Control procedures, i.e. the ongoing checks and calibrations

that are required on the CPC and sampling system during operation at a monitoring site. It is expected that

these will be the responsibility of users (network operators), though calibrations requiring test aerosols shall

only be carried out by suitably qualified laboratories. The main sources of measurement uncertainty are

described.
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1 Scope

This Technical Specification describes a standard method for determining the particle number concentration

7 –3

in ambient air in a range up to about 10 cm for averaging times equal to or larger than 1 min. The standard

method is based on a Condensation Particle Counter (CPC) operated in the counting mode and an appropriate

dilution system for concentrations exceeding the counting mode range. It also defines the performance

characteristics and the minimum requirements of the instruments to be used. The lower and upper sizes

considered within this document are 7 nm and a few micrometres, respectively. This document describes

sampling, operation, data processing and QA/QC procedures including calibration parameters.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated references,

the latest edition of the referenced document (including any amendments) applies.

ISO 27891, Aerosol particle number concentration — Calibration of condensation particle counters

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
actual flow rate

volumetric flow rate of an individual instrument, measured at its inlet under the actual air conditions

3.2
aerosol

a multi-phase system of solid and/or liquid particles suspended in a gas, ranging in particle size from

0,001 µm to 100 µm
3.3
calculation flow rate
flow rate which directly relates count rate and particle number concentration

Note 1 to entry: This flow rate is used for instrument internal calculation of the particle number concentration. It

depends on the instrument type and may be nominal, factory-certified or actual inlet flow rate. It may also include a

calibration factor unless the total inlet flow is analysed.
3.4
coincidence error

error that occurs with counting measuring methods when two or more particles are counted simultaneously

as a single particle

Note 1 to entry: Coincidence error is related to particle number concentration, flow velocity through the sensing

zone and size of sensing zone.
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3.5
detection efficiency

ratio of the particle number concentration determined by the measuring instrument to the reference particle

number concentration of the aerosol at the instrument's inlet

Note 1 to entry: The detection efficiency depends on particle size and may depend on particle number

concentration.
3.6
factory-certified flow rate

volumetric flow rate of an individual instrument at the time of factory calibration, measured at its inlet under

the actual air conditions, and documented on a check out certificate
3.7
nominal flow rate

volumetric flow rate indicated on the instrument specification sheet by the manufacturer

Note 1 to entry: The nominal flow rate is that flow rate, which a specific CPC model is designed for by the

manufacturer. The real flow rate of individual instruments may differ from the nominal flow due to manufacturing

tolerances.
3.8
number size distribution

frequency distribution of the particle number concentration represented as a function of particle size

3.9
particle
small piece of matter with defined physical boundary

Note 1 to entry: The phase of a particle can be solid, liquid, or between solid and liquid and a mixture of any of the

phases.
[SOURCE: ISO 27891:2015, modified]
3.10
particle number concentration
number of particles related to the unit volume of the carrier gas

Note 1 to entry: For the exact particle number concentration indication, information on the gaseous condition

(temperature and pressure) or the reference to a standard volume indication is necessary.

[SOURCE: ISO 27891:2015]
4 Atmospheric aerosol

Atmospheric aerosols are strongly dependent on their local and regional sources. Especially, the size

distribution in number and mass, as well as the size-resolved chemical composition are highly variable.

Aerosol particles are either emitted directly (primary aerosols) or formed by nucleation and condensation

from pre-cursor gases (secondary aerosol). Combustion processes lead to both primary and secondary

aerosols.

Mass-wise, the global direct emission of aerosol particles is dominated by sea salt, biological material as well

as by desert and volcanic dust. These particles are generally larger than 1 µm. Anthropogenic emissions in

this size range play a minor role on a global scale. Submicrometer natural aerosols consist mainly of marine

sulfate, biogenic organics, and wildfire carbonaceous particles. Submicrometer anthropogenic aerosols are

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complex mixtures of primary and secondary particles, consisting mainly of sulfate, nitrate, organics and

elemental carbon.

Particle number concentrations of atmospheric aerosols cover several orders of magnitude. While remote

marine or free tropospheric aerosols have number concentrations as low as tens or a few hundred per cubic

centimetre, anthropogenically influenced aerosols can contain a few thousand up to one million particles per

cubic centimetre. The number concentration of the anthropogenic aerosol over land, especially in urban areas

is dominated by particles in the size range smaller than 0,1 µm. Major sources for high number concentrations

in this size range are regional new particle formation and local combustion processes. Average background

concentrations in an urban area are several tens of thousands of particles per cubic centimetre.

For details see Annex E.
5 Description of the method
5.1 Sampling and conditioning
5.1.1 Sampling

The measurement of atmospheric aerosols will always necessitate sampling and the transport of the sample

to the measuring instrument. Moreover, in certain cases the sample has to be processed in terms of

temperature, relative humidity and particle concentration in order to adapt the aerosol to the measuring

instrument's permissible operating conditions.

The information given on this issue in this document refers to stationary ambient monitoring sites. For mobile

applications (e.g. measurements from aircraft), additional considerations have to be taken into account.

The measuring instruments shall be accommodated in a protected environment in controlled conditions

(temperature 15 °C to 30 °C).

The sampling location depends on the measurement task. If the undisturbed atmospheric aerosol is to be

measured, air intake should take place 5 m to 10 m above the ground level. Buildings, vegetation or the

topography of the terrain may make an even higher sampling point necessary. By contrast, the m

...

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