BS PD CEN TR 16013-2-2010 Workplace exposure — Guide nfor the use of direct-reading instruments for aerosol nmonitoring nPart 2 Evaluation of airborne particle nconcentra.pdf

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1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication PD 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 O

2、ptical Particle CountersPD CEN/TR 16013-2:2010 PUBLISHED DOCUMENT National foreword This Published Document is the UK implementation of CEN/TR 16013-2:2010. The UK participation in its preparation was entrusted to Technical Committee EH/2/2, Work place atmospheres. A list of organizations represente

3、d on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. BSI 2010 ISBN 978 0 580 69046 4 ICS 13.040.30 Compliance with a British Standard cannot confer

4、immunity from legal obligations. This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 2010 Amendments issued since publication Date Text affected August TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16013-2 May 2010 ICS 13.040

5、.30 English Version Workplace 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 surveill

6、ance des arosols - Partie 2 : 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 getrag

7、ener Partikel mit optischen Partikelzhlern 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,

8、France, Germany, Greece, Hungary, 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 KOMITE

9、E FR NORMUNG Management Centre: 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 4 Introduction .5 1 Scope 6 2 Principles of

10、the method .7 2.1 Light scattering 7 2.2 Working principle.7 3 OPC performance characteristics 8 4 Number and mass concentrations .8 5 Mass concentrations of thoracic and respirable aerosol fractions 9 6 OPC use . 10 6.1 General . 10 6.2 Airflow adjustment 11 6.3 Calibration of particle count respon

11、se . 11 6.4 Calibration of particle diameter response 11 6.5 Mass concentration response . 11 7 Fundamental and practical limitations . 12 7.1 Refraction index and particle density . 12 7.2 Forward scattering instruments 12 7.3 Limitation in particle size . 12 7.4 Coincidence error and concentration

12、 limitation 12 7.5 Aerosols from several sources . 12 8 Instrumentation characteristics 13 8.1 Aspiration system . 13 8.2 Integrated collection filter 13 8.3 Sampling head 13 8.4 Optical cell . 13 8.5 Electronics . 13 8.6 Case of laser instruments 13 9 Aerosol measurement by OPC 13 9.1 Operating pro

13、cedure 13 9.2 Cartography of workplace . 14 9.3 Working shift monitoring . 14 9.4 Sampling record 14 9.5 Cleaning and maintenance 14 Annex A (informative) Evaluation of an OPC as an instrument for thoracic and respirable mass concentrations 15 A.1 Introduction to workplace evaluation . 15 A.2 Proced

14、ure for field comparison of the OPC with the reference sampler 15 A.2.1 General . 15 A.2.2 Comparison of a static OPC with a static reference sampler 16 A.2.3 Comparison of mass concentrations for the respirable or thoracic aerosol fractions calculated from OPC data with a reference sampler . 16 A.3

15、 Calculation methods 16 A.3.1 General . 16 A.3.2 Estimation of the correction coefficient . 16 A.3.3 Exclusion of outliers 17 PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (E) 3 A.3.4 Residual uncertainty after transformation by the correction function 17 A.3.5 Equivalence 17 A.4 Periodic validation . 1

16、7 A.5 Documentation 18 A.5.1 General . 18 A.5.2 Description of the OPC and the reference sampler . 18 A.5.3 Critical review of sampling process 18 A.5.4 Circumstances of field comparison 18 A.5.5 Details of experimental design 18 A.5.6 Data analysis 18 A.5.7 Equivalence 19 A.6 Nomenclature . 19 Anne

17、x B (informative) Example for the determination of the correction coefficient for an OPC . 20 Bibliography 23 PD 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

18、 and biological agents”, 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 and/or CENELEC shall not be held responsible for identifying any or all such patent rights. CEN/TR 16013, Workpl

19、ace exposure Guide for the use of direct-reading instruments for aerosol monitoring, consists 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 con

20、centrations using photometers (in preparation) PD CEN/TR 16013-2:2010CEN/TR 16013-2:2010 (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 measure

21、ment of mass concentration and particle size estimation is indirect: a number of assumptions 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/

22、or the temporal evolution of an aerosol. In occupational hygiene, no standard recommends 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 estimat

23、ed mass concentrations from OPC data are only indicative and can not be used for a direct 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

24、distribution; estimating concentration variations and mean concentration of aerosol particles 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 Repo

25、rt describes the principle underlying evaluation of one or more health related aerosol 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 possibi

26、lities of: instantaneous (direct reading) measurement; time-related monitoring; investigation 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 (bagg

27、ing, sanding, etc.); identification of most exposed workers with a view to more detailed 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 concent

28、rations expressed in number of particles per unit volume of air. The applicability of the method is limited by the particle size and concentration ranges of OPC instruments, usually approximately 10 -1 m to 10 1m and 10 0particles/cm 3to 10 3particles/cm 3 , respectively. Depending on specific condi

29、tions, the OPC method allows filter collection of an aerosol fraction, in the best case close 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

30、 required to cover the size range of particles which can be detected and measured by the OPC optical 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

31、simplifying assumptions: identical optical parameters for both the calibration aerosol and the 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 tr

32、ansmission efficiencies of the OPC are known or estimated from engineering models. Therefore confirmation 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 indicat

33、ive and cannot be used for a direct comparison with a legally enforced occupational exposure limit. 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

34、diffraction. The amount of energy scattered can be calculated by applying Mies theory (see 8), which can be summarised by the following simplified equation for a non-polarised monochromatic incident light beam and a spherical particle: I = I 0 1 8 2 2 r 2 i 1 ,n, () + i 2 ,n, () (1) where I is the i

35、ntensity of light scattered at angle , per unit cross-sectional area, in watts per square metre; I 0is the intensity 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 i

36、s the particle complex refraction index; is the wavelength of incident light, in micrometres; r is the distance from the centre of the scattering particle to the point where the intensity, I, is measured, in micrometres; is the scattering angle; i 1 , i 2are Mie intensity functions. The particle dia

37、meter D can be deduced from Equation (1) by measuring the intensity of light scattered, when the particle optical parameters 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 characte

38、rised by their very low optical measuring volume (of the order of 1 mm 3 ) and by a flow rate often of the order of 1 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

39、measured. The aerosol to be investigated is aspirated through the instrument sampling probe by a constant flow pump. 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 prope

40、rties (complex refraction index, size, shape). Particles move perpendicularly to the plane formed by the focused light 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 focu

41、sed onto a photo detector and recorded as a pulse. From the pulse size, the particle size is inferred assuming spherical 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 1

42、6013-2:2010CEN/TR 16013-2:2010 (E) 8 3 OPC performance characteristics OPC performance characteristics vary according 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 optica

43、l arrangement (choice of scattering axis, width of reception solid angle), the sensitivity of the photosensitive component (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, restric

44、ts the chances of attaining aerodynamic conditions favourable to good aspiration orifice efficiency and ensuring full 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 los

45、ses are mainly inertial and therefore greater for larger particles (especially those larger than 10 m). Maximum concentration 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

46、optical sensing volume. 4 Number and mass concentrations OPC counting for a time t, in minutes, gives the number N of 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 n

47、umber of particles per unit volume of air C N : t Q N C = 001 , 0 N(2) where C Nis the particle number concentration in terms of number of particles per unit volume of air, in 1/cm 3 ; N is the number of particles counted; Q is the airflow aspirated by the OPC, in litres per minute; t is the time, i

48、n minutes. Mass concentration C mis expressed in particle mass per unit volume of air. Based on the assumption that particles are spherical and identify the particle geometrical diameter as its optical diameter, the mass of a particle classified in channel i, m ican be calculated from the equation:

49、3 12 6 10 i i D m = (3) where m iis the mass of a particle classified in channel i, in milligrams; D iis the mean diameter between channel i 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