CEN TR 16013-2-2010 Workplace exposure - Guide for the use of direct-reading instruments for aerosol monitoring - Part 2 Evaluation of airborne particle concentrations using Optica.pdf

1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationPD CEN/TR 16013-2:2010Workplace exposure Guidefor the use of direct-readinginstruments for aerosolmonitoringPart 2: Evaluation of airborne particleconcentrations using Optical Pa

2、rticleCountersPD CEN/TR 16013-2:2010 PUBLISHED DOCUMENTNational forewordThis Published Document is the UK implementation of CEN/TR 16013-2:2010.The UK participation in its preparation was entrusted to TechnicalCommittee EH/2/2, Work place atmospheres.A list of organizations represented on this commi

3、ttee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2010ISBN 978 0 580 69046 4ICS 13.040.30Compliance with a British Standard cannot confer immunity fromlegal obl

4、igations.This Published Document was published under the authority of theStandards Policy and Strategy Committee on 31 2010Amendments issued since publicationDate Text affectedAugustTECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16013-2 May 2010 ICS 13.040.30 English Version Workplace

5、 exposure - Guide for the use of direct-reading instruments for aerosol monitoring - Part 2: Evaluation of airborne particle concentrations using Optical Particle CountersExposition au poste de travail - Guide dutilisation des instruments lecture directe pour la surveillance des arosols - Partie 2 :

6、 Evaluation des concentrations de particules en suspension dans lair laide de compteurs optiques de particules Exposition am Arbeitsplatz - Leitfaden fr die Anwendung direkt anzeigender Gerte zur berwachung von Aerosolen - Teil 2: Ermittlung der Konzentration Luft getragener Partikel mit optischen P

7、artikelzhlern This Technical Report was approved by CEN on 13 March 2010. It has been drawn up by the Technical Committee CEN/TC 137. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hung

8、ary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centr

9、e: Avenue Marnix 17, B-1000 Brussels 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16013-2:2010: ECEN/TR 16013-2:2010 (E) 2 Contents Page Foreword 4Introduction .51 Scope 62 Principles of the method .72.1 Light scatterin

10、g 72.2 Working principle.73 OPC performance characteristics 84 Number and mass concentrations .85 Mass concentrations of thoracic and respirable aerosol fractions 96 OPC use . 106.1 General . 106.2 Airflow adjustment 116.3 Calibration of particle count response . 116.4 Calibration of particle diamet

11、er response 116.5 Mass concentration response . 117 Fundamental and practical limitations . 127.1 Refraction index and particle density . 127.2 Forward scattering instruments 127.3 Limitation in particle size . 127.4 Coincidence error and concentration limitation 127.5 Aerosols from several sources

12、. 128 Instrumentation characteristics 138.1 Aspiration system . 138.2 Integrated collection filter 138.3 Sampling head 138.4 Optical cell . 138.5 Electronics . 138.6 Case of laser instruments 139 Aerosol measurement by OPC 139.1 Operating procedure 139.2 Cartography of workplace . 149.3 Working shif

13、t monitoring . 149.4 Sampling record 149.5 Cleaning and maintenance 14Annex A (informative) Evaluation of an OPC as an instrument for thoracic and respirable mass concentrations 15A.1 Introduction to workplace evaluation . 15A.2 Procedure for field comparison of the OPC with the reference sampler 15

14、A.2.1 General . 15A.2.2 Comparison of a static OPC with a static reference sampler 16A.2.3 Comparison of mass concentrations for the respirable or thoracic aerosol fractions calculated from OPC data with a reference sampler . 16A.3 Calculation methods 16A.3.1 General . 16A.3.2 Estimation of the corr

15、ection coefficient . 16A.3.3 Exclusion of outliers 17PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 3 A.3.4 Residual uncertainty after transformation by the correction function 17A.3.5 Equivalence 17A.4 Periodic validation . 17A.5 Documentation 18A.5.1 General . 18A.5.2 Description of the OPC and the

16、 reference sampler . 18A.5.3 Critical review of sampling process 18A.5.4 Circumstances of field comparison 18A.5.5 Details of experimental design 18A.5.6 Data analysis 18A.5.7 Equivalence 19A.6 Nomenclature . 19Annex B (informative) Example for the determination of the correction coefficient for an

17、OPC . 20Bibliography 23PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 4 Foreword This document (CEN/TR 16013-2:2010) has been prepared by Technical Committee CEN/TC 137 “Assessment of workplace exposure to chemical and biological agents”, the secretariat of which is held by DIN. Attention is drawn to

18、 the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. CEN/TR 16013, Workplace exposure Guide for the use of direct-reading instruments for aerosol monitoring, co

19、nsists of the following parts: Part 1: Choice of monitor for specific applications Part 2: Evaluation of airborne particle concentrations using Optical Particle Counters Part 3: Evaluation of airborne particle concentrations using photometers (in preparation) PD CEN/TR 16013-2:2010CEN/TR 16013-2:201

20、0 (E) 5 Introduction Optical Particle Counters (OPC) count airborne particles and are therefore suitable for measuring concentrations expressed in number of particles per unit volume of air. Counting-based measurement of mass concentration and particle size estimation is indirect: a number of assump

21、tions and approximations are made to access the information sought. Nevertheless, optical particle counters can be used to evaluate the efficiency of preventive actions and to monitor the spatial distribution and/or the temporal evolution of an aerosol. In occupational hygiene, no standard recommend

22、s workers exposure assessment using optical particle counters. These instruments should instead be considered as permitting a complementary approach to the conventional filter-based gravimetric method. The estimated mass concentrations from OPC data are only indicative and can not be used for a dire

23、ct comparison with a legally enforced occupational exposure limit. An OPC method allows assessment of working place aerosol conditions including: almost instantaneous evaluation of particle concentration and size distribution; estimating concentration variations and mean concentration of aerosol par

24、ticles during a working shift period; sampling to constitute a particle sample for further analysis (when equipped with terminal filter). PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 6 1 Scope This Technical Report describes the principle underlying evaluation of one or more health related aerosol

25、fractions using an optical particle counter and details its limits and possibilities in the field of occupational hygiene. The method complements conventional long-term aerosol particle sampling and offers possibilities of: instantaneous (direct reading) measurement; time-related monitoring; investi

26、gation of space-related aerosol evolution (mapping); assessment of particle size distribution. The method enables e.g.: detection and relative quantification of concentration peaks due to specific operations (bagging, sanding, etc.); identification of most exposed workers with a view to more detaile

27、d studies of risks and prevention measures to be applied; detection of dust emission sources and their relative magnitudes. Basically, OPCs count airborne particles and are therefore suitable for measuring concentrations expressed in number of particles per unit volume of air. The applicability of t

28、he method is limited by the particle size and concentration ranges of OPC instruments, usually approximately 10-1 m to 101m and 100particles/cm3to 103particles/cm3, respectively. Depending on specific conditions, the OPC method allows filter collection of an aerosol fraction, in the best case close

29、to a health-related fraction (see EN 481), provided the OPC has the relevant sampling efficiency over its optical particle size range. If this is not the case, at least a sufficient aspiration efficiency is required to cover the size range of particles which can be detected and measured by the OPC o

30、ptical system. Converting count-based particle number concentrations into mass concentrations based on estimated particle size is indirect and therefore the accuracy of the conversion is limited by several simplifying assumptions: identical optical parameters for both the calibration aerosol and the

31、 measured workplace aerosol; all counted particles of the workplace aerosol are spherical with a geometric diameter equal to the determined optical diameter and with identical density; the aspiration and transmission efficiencies of the OPC are known or estimated from engineering models. Therefore c

32、onfirmation of the estimated mass concentrations from OPC particle size distributions by a conventional sampling method is necessary (see 3). The estimated mass concentrations from OPC data are only indicative and cannot be used for a direct comparison with a legally enforced occupational exposure l

33、imit. PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 7 2 Principles of the method 2.1 Light scattering An aerosol particle scatters light energy through the effects of reflection, refraction absorption, and diffraction. The amount of energy scattered can be calculated by applying Mies theory (see 8),

34、 which can be summarised by the following simplified equation for a non-polarised monochromatic incident light beam and a spherical particle: I = I01822r2i1,n,()+ i2,n,()(1) where I is the intensity of light scattered at angle , per unit cross-sectional area, in watts per square metre; I0is the inte

35、nsity of the incident beam, per unit cross-sectional area, in watts per square metre; is the particle size parameter, where D= and D is the spherical particle diameter, in micrometres; n is the particle complex refraction index; is the wavelength of incident light, in micrometres; r is the distance

36、from the centre of the scattering particle to the point where the intensity, I, is measured, in micrometres; is the scattering angle; i1, i2are Mie intensity functions. The particle diameter D can be deduced from Equation (1) by measuring the intensity of light scattered, when the particle optical p

37、arameters and the incident light beam characteristics are known. 2.2 Working principle OPCs are closed optical cell instruments featuring an aerosol aspiration system. They are characterised by their very low optical measuring volume (of the order of 1 mm3) and by a flow rate often of the order of 1

38、 l/min (see 9). This allows particles to be drawn individually into the sensing zone and recording of the light scattered by each particle. Discrete pulses are counted and their size measured. The aerosol to be investigated is aspirated through the instrument sampling probe by a constant flow pump.

39、Particles pass one by one into the optical cell, where each particle is illuminated by a focused light beam of specified characteristics and scatters this light according to its properties (complex refraction index, size, shape). Particles move perpendicularly to the plane formed by the focused ligh

40、t incident beam and the scattered light reception beam. Optical parts are swept by filtered air to prevent any particle deposition inside the optical cell. The scattered light is focused onto a photo detector and recorded as a pulse. From the pulse size, the particle size is inferred assuming spheri

41、cal particles. A quantity of signals during predefined integration time can be converted into mass concentration, usually after calibration using the investigated aerosol. PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 8 3 OPC performance characteristics OPC performance characteristics vary according

42、 to the aerosol particle sampling efficiency of the sampling head, the type of light used (monochromatic or polychromatic), its intensity (incandescent or laser lamp), the cell optical arrangement (choice of scattering axis, width of reception solid angle), the sensitivity of the photosensitive comp

43、onent (photodiode, photomultiplier) and the electronic discriminating power (pulse frequency and pulse size measurement). The limited flow rate, often of the order of 1 l/min, restricts the chances of attaining aerodynamic conditions favourable to good aspiration orifice efficiency and ensuring full

44、 transmission of particles to the optical cell. OPC flow rate system characteristics (aspiration orifice and tube geometries, air velocities and flow rates) are such that particle losses are mainly inertial and therefore greater for larger particles (especially those larger than 10 m). Maximum conce

45、ntration that can be measured by an OPC is limited to a few thousand particles per cubic centimetre to avoid coincidence error by passing several particles simultaneously through the optical sensing volume. 4 Number and mass concentrations OPC counting for a time t, in minutes, gives the number N of

46、 particles, counted and classified by size in different channels. Knowing the airflow Q aspirated by the OPC, it is simple to calculate the particle number concentration in terms of number of particles per unit volume of air CN: tQNC= 001,0N(2) where CNis the particle number concentration in terms o

47、f number of particles per unit volume of air, in 1/cm3; N is the number of particles counted; Q is the airflow aspirated by the OPC, in litres per minute; t is the time, in minutes. Mass concentration Cmis expressed in particle mass per unit volume of air. Based on the assumption that particles are

48、spherical and identify the particle geometrical diameter as its optical diameter, the mass of a particle classified in channel i, mican be calculated from the equation: 312610iiDm= (3) where miis the mass of a particle classified in channel i, in milligrams; Diis the mean diameter between channel i

49、left-hand and right-hand thresholds, in micrometres, as selected by the manufacturer or specified by the user; is the particle density, in kilograms per cubic metre. PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 9 The mass of all particles counted by the OPC is: =iiiNmm (4) where m is the mass of all particles counted by the OPC, in milligrams; miNi is the mass of particles classifie