Aerosol particle number concentration — calibration of condensation particle counters

Draft for Public Comment Form 36 DPC: 13 / 30271019 DC BSI Group Headquarters Date: 25 July 2013 Origin: International 389 Chiswick High Road London W4 4AL Tel: +44 (0)20 8996 9000 Fax: +44 (0)20 8996 7400 www.bsigroup.com Latest date for receipt of comments: 30 September 2013 Project No 2012/02766 Responsible committee: LBI/37 Particle characterization including sieving Interested committees: Title: Draft BS ISO 27891 Aerosol particle number concentration - Calibration of condensation particle number counters Please notify the secretary if you are aware of any keywords that might assist in classifying or identifying the standard or if the content of this standard i) has any issues related to 3rd party IPR, patent or copyright ii) affects other national standard(s) iii) requires additional national guidance or information WARNING: THIS IS A DRAFT AND MUST NOT BE REGARDED OR USED AS A BRITISH STANDARD THIS DRAFT IS NOT CURRENT BEYOND 30 September 2013 This draft is issued to allow comments from interested parties; all comments will be given consideration prior to publication No acknowledgement will normally be sent See overleaf for information on the submission of comments No copying is allowed, in any form, without prior written permission from BSI except as permitted under the Copyright, Designs and Patent Act 1988 or for circulation within a nominating organization for briefing purposes Electronic circulation is limited to dissemination by e-mail within such an organization by committee members Further copies of this draft may be purchased from BSI Shop http://shop.bsigroup.com or from BSI Customer Services, Tel: +44(0) 20 8996 9001 or email cservices@bsigroup.com British, International and foreign standards are also available from BSI Customer Services Information on the co-operating organizations represented on the committees referenced above may be obtained from http://standardsdevelopment.bsigroup.com Responsible Committee Secretary: Mr Simon Merriman (BSI) Direct tel: 0208 996 7462 E-mail: simon.merriman@bsigroup.com Introduction This draft standard is based on international discussions in which the UK has taken an active part Your comments on this draft are invited and will assist in the preparation of the consequent standard Comments submitted will be reviewed by the relevant BSI committee before sending the consensus UK vote and comments to the international secretariat, which will then decide appropriate action on the draft and the comments received If the international standard is approved, it is possible the text will be published as an identical British Standard UK Vote Please indicate whether you consider the UK should submit a negative (with reasons) or positive vote on this draft Submission of Comments - The guidance given below is intended to ensure that all comments receive efficient and appropriate attention by the responsible BSI committee Annotated drafts are not acceptable and will be rejected - All comments must be submitted, preferably electronically, to the Responsible Committee Secretary at the address given on the front cover Comments should be compatible with version 6.0 or version 97 of Microsoft Word for Windows, if possible; otherwise comments in ASCII text format are acceptable Any comments not submitted electronically should still adhere to these format requirements - All comments submitted should be presented as given in the example below Further information on submitting comments and how to obtain a blank electronic version of a comment form are available from the BSI website at: http://drafts.bsigroup.com/ Date: xx/xx/20xx Template for comments and secretariat observations (3) MB Clause No./ Subclause Paragraph/ No./Annex Figure/ (e.g 3.1) Table/Note 3.1 Definition Type of com- Commend (justification for change) by ment ed Document: ISO/DIS xxxx (6) (7) Proposed change by the MB Secretariat observations on each the MB comment submitted Definition is ambiguous and needs Amend to read ' so that the mains clarifying connector to which no connection ' The use of the UV photometer as an Delete reference to UV photometer EXAMPLE ONLY 6.4 Paragraph te alternative cannot be supported as serious problems have been encountered in its use in the UK Microsoft and MS-DOS are registered trademarks, and Windows is a trademark of Microsoft Corporation DRAFT INTERNATIONAL STANDARD ISO/DIS 27891 ISO/TC 24/SC Secretariat: DIN Voting begins on 2013-07-19 Voting terminates on 2013-10-19 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION Aerosol particle number concentration — Calibration of condensation particle counters Densité de particules d'aérosol — Étalonnage de compteurs de particules d'aérosol condensation ICS 19.120 To expedite distribution, this document is circulated as received from the committee secretariat ISO Central Secretariat work of editing and text composition will be undertaken at publication stage Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du secrétariat du comité Le travail de rédaction et de composition de texte sera effectué au Secrétariat central de l'ISO au stade de publication THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION © International Organization for Standardization, 2013 ISO/DIS 27891 COPYRIGHT PROTECTED DOCUMENT © ISO 2013 All rights reserved Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org Published in Switzerland ii © ISO 2013 – All rights reserved ISO/DIS 27891 Contents Page Foreword vi Introduction vii Scope Normative references Terms and definitions Symbols 5 5.1 5.2 5.3 5.4 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 5.4.6 5.4.7 5.5 Calibration using reference instruments – General principles General principles Objectives for the calibration aerosol Setup overview Components and their requirements Primary aerosol source Charge conditioner 10 DEMC 11 Make-up or bleed air 11 Mixing device, flow splitter and connection tubing 11 Reference instrument: FCAE or CPC 12 Other tools 13 Differences between FCAE and CPC as a reference instrument 13 6.1 6.2 6.2.1 6.2.2 6.2.3 6.2.4 6.2.5 6.2.6 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.3.8 6.4 6.4.1 6.4.2 6.4.3 Calibration using an FCAE as reference instrument 15 Overview of the setup and calibration procedure 15 Preparation 17 Primary aerosol 17 Other equipment 17 DEMC 17 FCAE 18 Test CPC 19 Check of the complete setup 20 Calibration procedure of detection efficiency 22 DEMC diameter adjustment 22 Primary aerosol adjustment 22 Splitter bias β measurement 23 Test CPC efficiency measurement 23 Measurement of different particle concentrations 25 Measurement of different sizes 25 Repetition of first measurement point 25 Preparation of the calibration certificate 25 Measurement uncertainty 25 Particle size 26 Detection efficiency 26 Particle number concentration 27 7.1 7.2 7.2.1 7.2.2 7.2.3 7.2.4 Calibration using a CPC as reference instrument 28 Overview of the setup and calibration procedure 28 Preparation 30 Primary aerosol 30 Other equipment 30 DEMC 30 Reference CPC 31 © ISO 2013 – All rights reserved iii ISO/DIS 27891 7.2.5 7.2.6 7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 7.3.7 7.3.8 7.4 7.4.1 7.4.2 7.4.3 Test CPC 32 Check of the complete setup 32 Calibration procedure of detection efficiency 34 DEMC diameter adjustment 34 Primary aerosol adjustment 35 Splitter bias β measurement 36 Test CPC efficiency measurement 36 Measurement of different particle concentrations 37 Measurement of different sizes 37 Repetition of first measurement point 37 Preparation of the calibration certificate 38 Measurement uncertainty 38 Particle size 38 Detection efficiency 38 Particle number concentration 39 Reporting of results 39 Annex A.1 A.2 A.3 A.3.1 A.3.2 A (informative) CPC performance characteristics 41 Introduction 41 Major performance characteristics of a CPC 41 Examples 43 Linearity 44 Lower detection limit 48 Annex B (informative) Effect of particle surface properties on the CPC detection efficiency 49 Annex C (informative) Example calibration certificates 50 C.1 Introduction 50 C.2 Example completed certificate for a CPC calibrated against an FCAE 51 C.3 Example blank certificate for a CPC calibrated against a reference CPC 53 C.4 Example blank calibration certificate for an FCAE 55 C.5 Example blank calibration certificate for a reference CPC 57 Annex D (normative) Calculation of the CPC detection efficiency 59 D.1 General 59 D.2 Calibration in the size range where the detection efficiency of the test CPC is known to be constant against size 60 D.3 Calibration in the size range where the detection efficiency of the test CPC varies with size 61 Annex E (normative) Procedures relating to multiply charged particles 63 E.1 General 63 E.2 Determination of the fraction of multiply charged particles using multiple DEMC voltages 63 E.2.1 Principle 63 E.2.2 For calibration with an FCAE 64 E.2.3 For calibration with a reference CPC 65 E.3 Measurement of the fraction of multiply charged particles with DMAS 66 Annex F (informative) Traceability diagram 69 Annex G (informative) Diluters 71 G.1 Introduction 71 G.2 Dilution bridge 71 G.3 Dilution loop 72 G.4 Dilution by addition of clean air and bleeding of excess air 72 G.5 Other dilution methods 72 Annex H (normative) Evaluation of the concentration bias correction factor between the inlets of the reference instrument and test CPC 73 H.1 General 73 H.2 Measurement of the bias correction factor β for equal detector flow rates 73 H.2.1 Measurement in the first configuration 73 H.2.2 Measurement in the second configuration 74 iv © ISO 2013 – All rights reserved ISO/DIS 27891 H.2.3 H.2.4 H.3 Measurement repeated in the first configuration 75 Calculation of β and the associated uncertainty 75 Measurement of the bias correction factor β for unequal detector flow rates 76 Annex I (informative) Extension of calibration range to lower concentrations 78 I.1 Introduction 78 I.2 Diluter 78 I.2.1 Diluter requirements 78 I.2.2 Diluter validation: the effect of particle concentration on flow rate 79 I.3 Proportionality calibration 80 I.3.1 Experimental setup 80 I.3.2 CPC zero 81 I.3.3 CPC correlation 81 I.3.4 Proportionality measurements 81 I.4 Data analysis and test acceptance 82 I.4.1 Dependence of dilution ratio with concentration 82 I.4.2 Dependence of dilution ratio with time 83 I.5 Uncertainty analysis 84 Annex J (informative) Example of a detection efficiency measurement 85 J.1 Overview of the calibration setup and procedure (see 6.1 of main text) 85 J.2 Preparation (see 6.2 of main text) 86 J.2.1 Primary aerosol 86 J.2.2 DEMC 86 J.2.3 FCAE 86 J.2.4 Test CPC 87 J.2.5 Other equipment 88 J.2.6 Check of the complete setup 88 J.3 Calibration procedure of detection efficiency (see 6.3 of main text) 88 J.3.1 DEMC diameter adjustment 88 J.3.2 Primary aerosol adjustment 89 J.3.3 Splitter performance 90 J.3.4 Test CPC detection efficiency 92 J.4 Uncertainty 93 J.5 An example protocol for calibration with an FCAE 95 Annex K (normative) Volumetric flow rate calibration 99 Annex L (normative) Testing the charge conditioner and the DEMC at maximum particle number concentration 101 Annex M (informative) A recommended data recording method 102 M.1 General 102 M.2 DEMC voltage cycling for repeated concentration measurements 102 Annex N (informative) Uncertainty of detection efficiency due to particle size uncertainty 104 Annex O (informative) Application of calibration results 106 Bibliography 108 © ISO 2013 – All rights reserved v ISO/DIS 27891 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work of preparing International Standards is normally carried out through ISO technical committees Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part The main task of technical committees is to prepare International Standards Draft International Standards adopted by the technical committees are circulated to the member bodies for voting Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights ISO shall not be held responsible for identifying any or all such patent rights ISO 27891 was prepared by Technical Committee ISO/TC 24, Particle characterization including sieving, Subcommittee SC 4, Particle characterization This second/third/ edition cancels and replaces the first/second/ edition (), [clause(s) / subclause(s) / table(s) / figure(s) / annex(es)] of which [has / have] been technically revised This ISO 27891 is the first edition It does not consist of other parts vi © ISO 2013 – All rights reserved ISO/DIS 27891 Introduction A condensation particle counter (CPC) is a measuring device for number concentration of small aerosol particles The common principle of all different CPC types is that condensation of supersaturated vapours is used to grow ultra-fine and nanoparticles to droplets of sizes that can be detected optically [1] The counting of the droplets is performed via optical light scattering The droplet passes through a detection area where it is illuminated by a focused light beam and a portion of the scattered light is detected with a photodetector The frequency of this event leads, with the known volume of sampled air, to the particle number concentration At low concentrations the CPC counts individual particles and allows an absolute determination of particle number concentration Commercially available CPCs employ different working fluids to generate the vapour, e.g butanol, isopropyl alcohol, or water Moreover, different principles are in use to achieve the needed supersaturation in the sample air The most common CPC uses laminar flow and diffusional heat transfer The diffusion constant of the working fluid determines the needed heating or cooling steps to initiate condensation and hence the principle design of a laminar flow CPC Less common are turbulent mixing CPCs: In these CPCs the supersaturation is achieved by turbulently mixing the sample air with a particle free gas flow saturated with the working fluid The figure below shows a schematic of the probably most common CPC type with a laminar flow through a heated saturator and a cooled condenser 12 10 11 1 Aerosol inlet Working fluid reservoir Heated saturator Nanoparticle Thermoelectric cooling and heating device Condenser Droplet Light source 10 11 Illumination optics Receiving optics Photodetector 12 Aerosol outlet Figure — Principle of a laminar flow CPC © ISO 2013 – All rights reserved vii ISO/DIS 27891 The accuracy of CPC measurements, however, depends on various influences For example, if the flow rate had an error, the concentration would have an error Coincidence error at very high concentration, inefficient activation of particle growth at very small sizes, and losses of particles during transport from the inlet to the detection section are other possible sources of errors For accurate measurement, the CPC shall be calibrated 'Calibration' of the CPC is usually done using a Faraday-cup aerosol electrometer (FCAE) as reference instrument [2,3] In many cases, the purpose of the ‘calibration’ is to determine the limit of particle detection at very small size The FCAE has been used as the reference since the detection efficiency of the FCAE was considered to be unity at any size The detection efficiency of a CPC is determined as the ratio of the concentration indicated by the CPC under calibration to that by the FCAE, while aerosols of singly-charged, size-classified particles of the same number concentration are supplied simultaneously to both instruments This Standard sets out two distinct methods of CPC calibration: characterisation of a CPC by comparison with an FCAE, which is the same as the traditional approach described above; and by comparison with a reference CPC In the former case, the method includes procedures to validate the FCAE Alternatively, an FCAE that has a reputable calibration certificate, covering the relevant particle number concentrations, sizes and composition, can be used In the latter case, the reference CPC is one that has a reputable calibration certificate, again covering the relevant particle number concentrations, sizes and composition A reputable calibration certificate shall mean either one that has been produced by a laboratory accredited to ISO/IEC 17025 or an equivalent standard, where the type and range of calibration is within the laboratory’s accredited scope, or a European Designated Institute or a National Metrology Institute that offers the relevant calibration service and whose measurements fulfil the requirements of ISO 17025 Two major sources of errors are known in CPC calibration; the presence of multiply-charged particles and the bias of the particle concentrations between the inlet of the CPC under calibration and that of the reference instrument Evaluation of these factors and corrections for them shall be included in the calibration procedure, the methods of which are specified in this Standard This Standard is aimed at:  users of CPCs (e.g., for environmental or vehicle emissions purposes) who have internal calibration programmes;  CPC manufacturers who certify and recertify the performance of their instruments; and  technical laboratories who offer the calibration of CPCs as a service, which can include National Metrology Institutes who are setting up national facilities to support number concentration measurements viii © ISO 2013 – All rights reserved ISO/DIS 27891 6.3 6.3.1 6.3.2 Detection efficiencies DEMC diameter adjustment (70 nm) Primary aerosol adjustment The concentration is within the capability of the charge conditioner Voltage Size [nm] FCAE [fC/s] -3 CCPC [cm ] 1U -767 70 19 6871 2U -1533 103 5.8 2229 3U -2300 130 1.3 447 CFCAE [cm-3] 7491 2287 513 f103nm,+1 0.2146 f103nm,+2 0.0333 f130nm,+1 0.2168 f130nm,+3 0.0048 CN(2U) 355.9 CN(3U) 11.38 CN(U) 6767 CN 7135 φ1 0.9485 φ2 0.0499 φ3 Ф ФLIMIT Result 0.0016 0.0515 < 0.1 ok Concentration within the range of the FCAE The FCAE current of 19 fC/s is above the lower limit of detection and lso below the max of the FCAE Splitter bias β measurement 6.3.3 Configuration test zero i =1 zero i =2 zero i =3 zero i =4 zero i =5 zero FCAE [fC/s] CPC [cm-3] FCAE [cm-3] 0.4 19.5 6970 7135 0.5 19.1 6980 6966 0.5 19.5 6980 7097 0.6 19.8 6960 7228 0.4 19.5 6970 7116 0.6 Configuration -3 -3 test FCAE [fC/s] CPC [cm ] FCAE [cm ] zero 0.5 i =1 19.6 6970 7135 zero 0.6 i =2 19.6 6980 7154 zero 0.4 i =3 19.6 6970 7172 zero 0.5 i =4 19.6 6960 7172 zero 0.4 i =5 19.6 6970 7154 zero 0.6 © ISO 2013 – All rights reserved r1 0.9769 1.0020 0.9835 0.9629 0.9795 r2 0.9769 0.9757 0.9718 0.9704 0.9743 97 ISO/DIS 27891 Configuration 1, repeat test FCAE [fC/s] CPC [cm-3] FCAE [cm-3] zero 0.2 i =1 19.2 7001 7079 zero 0.4 i =2 19.6 6965 7135 zero 0.7 i =3 19.4 6970 7022 zero 0.6 i =4 19.7 6940 7172 zero 0.5 i =5 19.3 6975 7022 zero 0.6 0.9823 stdev r1 0.0121 0.9738 β 0.9957 Limits 0.95 - 1.05 stdev r2 u(β) 0.0027 0.0088 6.3.4 r1 0.9890 0.9762 0.9925 0.9676 0.9932 Test CPC efficiency measurementsat the specific diameter and concentration: Recorded data test FCAE [fC/s] stdev [fC/s] 0.3 0.2 19.3 0.2 0.3 0.2 19 0.3 0.3 0.2 19.4 0.3 0.4 0.2 18.8 0.2 0.4 0.2 19.5 0.1 0.5 0.2 zero i =1 zero i =2 zero i =3 zero i =4 zero i =5 zero -3 CPC [cm ] 0.1 6887.4 0.1 6807.4 0.1 6914.7 0.3 6712.2 0.1 6908.2 1.6 stdev [cm-3] 0.1 31.6 0.1 64.8 0.1 59.9 0.3 42 0.1 34.2 1.4 CPC CoV [%] 0.46 0.95 0.87 0.63 0.50 Calculated values FCAE [fC/s] FCAE [cm-3] FCAE, β [cm-3] 19.0 7490.6 7523.2 18.7 7372.4 7404.4 19.1 7510.3 7543.0 18.4 7254.1 7285.6 19.1 7510.3 7543.0 i stdev η 0.9635 0.0026 ηCPC 0.9612 0.9653 0.9625 0.9673 0.9616 max difference from mean 0.0037