SIST EN 16897:2017
(Main)Workplace exposure - Characterization of ultrafine aerosols/nanoaerosols - Determination of number concentration using condensation particle counters
Workplace exposure - Characterization of ultrafine aerosols/nanoaerosols - Determination of number concentration using condensation particle counters
For occupational exposure to ultrafine aerosols and nanoaerosols, exposure metrics like the number and surface area concentration are important. This European Standard provides a guideline to determine the occupational exposure to airborne particles (expressed as number concentration of ultrafine aerosols and nanoaerosols) by use of condensation particle counters (also called CPC’s). Principles of operation, problems of sampling in the workplace environment, calibration, equipment maintenance, measurement uncertainty, and reporting of measurement results are covered. Potential problems and limitations are described and need to be addressed when limit values are fixed in the future and compliance measurements are carried out.
Exposition am Arbeitsplatz - Charakterisierung ultrafeiner Aerosole/Nanoaerosole - Bestimmung der Anzahlkonzentration mit Kondensationspartikelzählern
Diese Europäische Norm gibt Leitlinien zur Messung der Feinpartikelfraktion des Aerosols, insbesondere für die Bestimmung der Anzahlkonzentration von ultrafeinen Aerosolen und Nanoaerosolen am Arbeitsplatz unter Verwendung von Kondensationspartikelzählern (CPC).
Diese Europäische Norm behandelt die Grundlagen der Bedienung von CPCs, Probleme der Probenahme im Umfeld des Arbeitsplatzes, Aspekte für die Auswahl eines geeigneten Messgeräts, Anwendungsgrenzen, die Verwendung von unterschiedlichen Arbeitsflüssigkeiten und Technologien, Kalibrierung, Wartung des Geräts, Messunsicherheit und Angabe der Messergebnisse. Beschrieben werden potenzielle Probleme und Einschränkungen, die von Bedeutung sind, wenn Messungen am Arbeitsplatz durchgeführt werden.
Exposition sur les lieux de travail - Caractérisation des aérosols ultrafins/nanoaérosols - Détermination de la concentration en nombre à l'aide de compteurs de particules à condensation
La présente Norme européenne fournit des lignes directrices sur le mesurage de la fraction particulaire fine de l'aérosol, notamment pour la détermination de la concentration en nombre des aérosols ultrafins et des nanoaérosols sur les lieux de travail à l'aide de compteurs de particules à condensation (CPC).
La présente Norme européenne traite du principe de fonctionnement d'un CPC, des problèmes d'échantillonnage dans l'environnement des lieux de travail, des aspects relatifs au choix d'un instrument approprié, des limites d'application, de l'utilisation de différents fluides de travail et technologies, de l'étalonnage, de la maintenance de l'équipement, de l'incertitude de mesure et du compte-rendu des résultats de mesure. Les problèmes potentiels et les limitations qui sont pertinents pour les mesurages sur les lieux de travail sont décrits.
Izpostavljenost na delovnem mestu - Karakterizacija ultrafinih aerosolov/nanoaerosolov - Določevanje številčne koncentracije z uporabo kondenzacijskega števca delcev
Za poklicno izpostavljenost ultrafinim aerosolom/nanoaerosolom so pomembne meritve izpostavljenosti, kot so številčna in površinska koncentracija. Ta evropski standard podaja smernice za ugotavljanje poklicne izpostavljenosti delcem v zraku (izražene kot številčna koncentracija ultrafinih aerosolov in nanoaerosolov) z uporabo kondenzacijskih števcev delcev (imenovanih tudi CPC). Standard zajema načela delovanja, težave z vzorčenjem v delovnem okolju, umerjanje, vzdrževanje opreme, merilno negotovost in poročanje o rezultatih meritev. Morebitne težave in omejitve so opisane in jih je treba upoštevati, kadar so določene mejne vrednosti in se izvajajo meritve skladnosti.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 16897:2017
01-september-2017
,]SRVWDYOMHQRVWQDGHORYQHPPHVWX.DUDNWHUL]DFLMDXOWUDILQLK
DHURVRORYQDQRDHURVRORY'RORþHYDQMHãWHYLOþQHNRQFHQWUDFLMH]XSRUDER
NRQGHQ]DFLMVNHJDãWHYFDGHOFHY
Workplace exposure - Characterization of ultrafine aerosols/nanoaerosols -
Determination of number concentration using condensation particle counters
Exposition am Arbeitsplatz - Charakterisierung ultrafeiner Aerosole/Nanoaerosole -
Bestimmung der Anzahlkonzentration mit Kondensationspartikelzählern
Exposition sur les lieux de travail - Caractérisation des aérosols ultrafins/nanoaérosols -
Détermination de la concentration en nombre à l'aide de compteurs de particules à
condensation
Ta slovenski standard je istoveten z: EN 16897:2017
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
SIST EN 16897:2017 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 16897:2017
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SIST EN 16897:2017
EN 16897
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2017
EUROPÄISCHE NORM
ICS 13.040.30
English Version
Workplace exposure - Characterization of ultrafine
aerosols/nanoaerosols - Determination of number
concentration using condensation particle counters
Exposition sur les lieux de travail - Caractérisation des Exposition am Arbeitsplatz - Charakterisierung
aérosols ultrafins/nanoaérosols - Détermination de la ultrafeiner Aerosole/Nanoaerosole - Bestimmung der
concentration en nombre à l'aide de compteurs de Anzahlkonzentration mit
particules à condensation Kondensationspartikelzählern
This European Standard was approved by CEN on 10 April 2017.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
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, Serbia, 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
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16897:2017 E
worldwide for CEN national Members.
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EN 16897:2017 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Abbreviations . 6
5 Principle . 6
6 Measurement methods . 8
6.1 General . 8
6.2 Exposure measurement . 9
6.3 Emission measurement . 9
6.4 Background measurement . 9
7 Measurement procedure . 10
7.1 Selection of suitable instrument . 10
7.2 Preparation . 10
7.3 Monitoring . 10
7.4 Sampling line . 10
7.5 Use of a diluter . 10
8 Presentation and evaluation of data . 11
9 Check of CPC performance . 11
10 Problems and uncertainties . 12
10.1 CPC counting efficiency . 12
10.2 Sampling losses . 13
10.2.1 General . 13
10.2.2 Diffusion losses in a sampling tube . 13
10.2.3 Internal CPC losses . 14
10.3 Uncertainties . 15
10.4 Maintenance . 15
Annex A (informative) Results of pre-normative research — Laboratory comparisons of
CPCs . 16
Annex B (informative) List of CPC instruments . 17
Bibliography . 23
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European foreword
This document (EN 16897:2017) 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.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2017, and conflicting national standards
shall be withdrawn at the latest by December 2017.
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.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: 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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
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Introduction
Within occupational hygiene, aerosol concentrations have been traditionally measured in terms of mass
concentrations. For ultrafine aerosols and nanoaerosols, other exposure metrics such as the number
and surface area concentrations could become important for predicting health effects with some
aerosols, depending on their chemical and physical properties. Even if actual occupational exposure
metrics have not been established, this European Standard can be used by occupational hygienists and
researchers to measure airborne particle concentrations in workplaces.
Recommendations on how to perform an assessment of inhalation exposure to nano-objects and their
agglomerates and aggregates (NOAA), including which measurement strategy to adopt, will be provided
in prEN 17058:2016 [16].
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1 Scope
This European Standard gives guidelines on the measurement of the fine particle fraction of the aerosol,
especially for the determination of the number concentration of ultrafine aerosols and nanoaerosols at
workplaces by use of condensation particle counters (CPC).
This European Standard deals with the CPC's principle of operation, problems of sampling in the
workplace environment, aspects for selecting a suitable instrument, limits of application, use of
different working fluids and technologies, calibration, equipment maintenance, measurement
uncertainty, and reporting of measurement results. Potential problems and limitations which are of
relevance for workplace measurements are described.
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.
EN 1540, Workplace exposure - Terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 1540 and the following apply.
3.1
background (particle) measurement
measurement of the particle concentration, at a location or a time not affected by the activity/process
under investigation
3.2
emission (particle) measurement
measurement of the particle concentration in direct vicinity of a process or machine
3.3
(particle) (electrical) mobility (equivalent) diameter
diameter of a sphere carrying one elementary electric charge with the same electrical mobility as the
particle in question
3.4
exposure (particle) measurement
measurement of the particle concentration close to a worker, preferably in the breathing zone of a
worker
Note 1 to entry: Measurements performed outside the breathing zone give only an approximated exposure
value.
3.5
nanoaerosol
aerosol comprised of, or consisting of, nano-objects and nanostructured particles
[SOURCE: ISO/TR 27628:2007, definition 2.11] [17]
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3.6
nano-object
material with one, two or three external dimensions in the nanoscale below 100 nm
Note 1 to entry: Generic term for all discrete nanoscale objects.
[SOURCE: CEN ISO/TS 80004-1:2015, definition 2.5] [18]
3.7
particle number concentration
C
N
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) is necessary. This can include a comparison of the measured number concentration
with the test certificate of a CPC or a correction of the nominal flow with the actual volumetric flow. A frequent
check of the instrument including its air flow and response is strongly recommended.
Note 2 to entry: In many cases, depending on make and model, the CPC outputs the particle number
concentration based on the assumption that its air flow rate equals the nominal air flow rate determined at a
specific testing condition.
−3
Note 3 to entry: The particle number concentration is given as number per cubic centimetre [cm ].
3.8
ultrafine particle
particle with a nominal diameter (such as geometric, aerodynamic, mobility, projected-area or
otherwise) of 100 nm or less
Note 1 to entry: The term is often used in the context of particles produced as a by-product of a process
(incidental particles), such as welding fume and combustion fume.
[SOURCE: ISO/TR 27628:2007, definition 2.21]
4 Abbreviations
For the purposes of this document, the following abbreviations apply.
CMMD Count Median Mobility Diameter of a particle size distribution
CNC Condensation Nuclei Counter
CPC Condensation Particle Counter
5 Principle
The common principle of all different CPC types is the condensation of supersaturated vapours onto
particles. Particles grow to droplets of sizes that can be detected optically [1]. The counting of the
droplets is performed via optical light scattering.
A CPC measures, in real-time, airborne particles ranging from few nm up to several µm in size in a
limited range of concentration, but does not discriminate between particles of different sizes or origin.
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Aerosol particles are drawn into the instrument at the inlet. A pre-separation can be applied to avoid
large particles that otherwise would have been trapped in the aerosol transfer tubes of the instrument.
A part or the entire air flow is directed into a heated saturator. Commercially available CPCs employ
different working fluids to generate the vapour, e.g. butanol, iso-propanol, 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 and saturation vapour pressure
of the working fluid determines the needed heating or cooling steps to initiate condensation and hence
the principle design of a laminar flow CPC. The mixture of particles and supersaturated vapour reaches
the condensation zone and the vapour condenses onto the particles. The size of the droplets reaches
diameters of up to a few micrometres in the condenser zone. The droplet passes through a detection
zone 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 a
direct determination of particle number concentration (single particle count mode). At higher
concentrations some instruments include an evaluation of the total scattered light intensity without
single particle counting and thus estimate the number concentration, based on assumptions of final
particle size and optical properties (photometric mode).
NOTE Another name given to CPC is condensation nuclei counter (CNC).
Figure 1 shows a schematic of the probably most common CPC type with a laminar flow through a
heated saturator and a cooled condenser.
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Key
1 aerosol inlet 7 droplet
2 working fluid reservoir 8 light source
3 heated saturator 9 illumination optics
4 particle 10 receiving optics
5 thermoelectric cooling and heating device 11 photodetector
6 condenser 12 aerosol outlet
Figure 1 — Principle of the laminar flow CPC
6 Measurement methods
6.1 General
The CPC measures the number concentration of an aerosol in real-time within a defined range of
particle diameters and concentrations. A comparison to mass based occupational limit values of
airborne hazardous substances is not possible.
Analytical scanning electron microscopy or transmission electron microscopy can be used for the off-
line analysis of airborne particles collected on an appropriate substrate and can provide additional
chemical, morphological and size information of the nanoaerosols to data obtained using a CPC or
another real-time number concentration instrument (see ISO/TR 27628 [17]) The application of CPCs
for environmental measurements is described in [19].
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6.2 Exposure measurement
Measurements near to or in the breathing zone of a worker can be carried out to get information on
personal exposure. Since CPC instruments are available as static or mobile monitors, a sampling
position representative for the personal exposure shall be found. This could e.g. be done with the use of
sampling tubes, as specified in 7.4. Workplace air flow pattern characteristics, e.g. direction of air flow
relative to particle-emitting source and sampling position, and the presence of multiple particle-
emitting sources are essential for either selection of a sampling position or interpretation for worker
exposure.
For workers moving around, a different sampling strategy (e.g. time weighted averaging of exposure
data from different sampling locations) might be necessary to adopt.
NOTE For some workplace conditions, it is not possible to find a representative sampling position. In these
cases, the measured concentrations are less reliable and only estimates of worker’s exposure.
General information about measurement strategy in workplaces can be found in EN 689 [20]. Further
detailed information on tiered approaches for determining and assessing exposure to manufactured
nanomaterials can be found in [2] and [16]. These approaches consist in general of an initial assessment
(mainly based on information gathering), a basic exposure measurement, and an expert exposure
assessment.
6.3 Emission measurement
The determination of the emission from a task, a process or a machine can be performed by using a CPC
at a representative position. Both static and mobile instruments can be used. Differences in the
instrument’s particle size range and concentration range need to be taken into account. Air flows and
emission directions shall be checked prior to the measurement. General information about the use of
emission measurements for risk assessment can be found in EN 689.
By changing the position of measurement, an overview of particle-emitting sources in the workplace
area or map of particle number concentrations can be achieved [3].
6.4 Background measurement
The influence of several particle-emitting sources of airborne particles (indoor and outdoor sources) on
the number concentration at the workplace can be crucial. It is important to know the contribution
from those particle-emitting sources (also called background) to the task or process emission or
exposure concentration when determining the specific number concentration coming from the task or
work process under investigation. External particle-emitting sources often consist of unintentionally
created particles and might need to be discriminated from the object of measurement.
In the workplace, the background measurement can be realized with a spatial or a time dependent
approach. For the spatial approach, two CPCs are used simultaneously and the number concentrations
are compared. One CPC, often referred to near-field instrument, is positioned near or in the breathing
zone of the worker or near the task or process. In an ideal condition, the other CPC, often referred as
far-field instrument, is placed at a distant location where the nano-object emission source is not
detected and where the background signature is the same as the one measured by the near-field CPC.
The time dependent approach is realized with one instrument located near or in the breathing zone of
the worker or near the task or process and the time periods with and without the nanomaterial related
task or process in operation are compared. Details about the assessment of inhalation exposure to
nano-objects including the measurement strategy are described in [16].
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7 Measurement procedure
7.1 Selection of suitable instrument
The user shall be aware of the fact that it can be possible that a specific type of CPC cannot measure the
whole size distribution and concentration range of the ultrafine particles/nano-objects at the
workplace. See Annex A for more information.
In some cases the size of the aggregated/agglomerated particles can be significantly above the upper
range of CPCs. This can occur when handling nanostructured powders. In these cases, a CPC shall be
combined with another instrument (e.g. optical particle counter, optical particle sizer). In the case of
process generated particles (e.g. thermal processes), practical experience shows that the maxima of the
particle number size distributions lie between approximately 10 nm and 500 nm, depending on the
occurrence of primary, aggregated and agglomerated ultrafine particles/nano-objects. The total number
3
concentration found at workplaces varies between 10 particles per cubic centimetre in clean air
8
environment and 10 particles per cubic centimetre in welding plumes [4]. Hand-held CPCs usually
show less sensitivity for small particles (<20 nm) than stationary instruments. The upper limit of the
concentration range always needs to be considered. Attention shall be paid for the measurement of
hydrophobic particles, as not all types of CPCs allow their measurement. Some information is included
in Annex B. The instruments shall be used in a certain temperature range, usually between 10 °C and
35 °C (as specified by the manufacturer).
7.2 Preparation
The CPC shall be checked regularly, including its air flow, especially before and after a series of
measurements (see Clause 9). Before performing a series of measurements, a zero check of the CPC
shall be carried out applying high efficiency particle arrestor (HEPA) filters to the sampling line.
Comparing it to another CPC before and after a series of measurements is strongly recommended.
7.3 Monitoring
Diffusion losses in the line shall be taken into account and reported, if information on the size
distribution is available (see 10.2). Otherwise the report shall state that no correction for diffusion
losses has been carried out.
The instrument’s measurement time interval can be selected from 1 s to a few hours. Especially for
highly fluctuating concentrations, such as in welding workplaces, the shortest time interval is
recommended. The duration of an exposure measurement shall be at least 15 min up to a whole shift
(usually 8 h). The minimum recording time for emission measurements shall be at least 15 min
(see [16]).
7.4 Sampling line
The aerosol can be sampled with a flexible tube (e.g. in order to access the breathing zone of a worker).
The material of the tube shall be an electrical conductor. Particle diffusion losses shall be minimized.
This can be accomplished by using tubes of length as short as possible. The flow in the sampling line
shall be laminar. A maximum flow can be calculated in dependence of the inner tube diameter (see [5]).
7.5 Use of a diluter
If the maximum concentration of the instrument is reached or exceeded, a dilution with particle-free air
can be used. Otherwise, the data at or above this limit cannot be used as a quantitative result, but can be
useful as a lower limit of exposure, keeping in mind that the real exposure can be considerably higher. A
dilution system could introduce a relatively high uncertainty to the measurement, as it might not be
stable over a wide particle size and concentration range. Suitable dilution systems are described in
[6], [7].
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8 Presentation and evaluation of data
The recorded time series are the basis for the evaluation of workplace processes and for generating
statistical values. Therefore it is recommended to keep them for later usage.
The resulting particle number concentration C shall be given as arithmetic average value, geometric
N
average value, and minimum and maximum values over the selected assessment period (e.g. 15 min or
8 h) or as a time series. The instruments’ measurement time interval and the averaging time of the data
evaluation shall be reported.
The concentration values measured only represent the concentration within the particle size range of
the CPC. Because particles outside the particle size range are not detected, the particle size range of the
CPC shall always be reported. If a particle size pre-separator is mounted upstream of the CPC, its
separation efficiency (as a function of particle size) shall be given.
Depending on the objective of the measurements, the number concentration data can be presented in
different ways, for example
— as a comparison of different exposure situations,
— as temporal occurrence of peaks related to process steps or workplace activities in an exposure
scenario,
NOTE This requires an activity log.
— as time series in form of a diagram to illustrate and compare the workplace processes. Video
captures may also be used in combination with the time series.
Guidelines on the evaluation of data will be provided in [16]. All relevant instrument parameters like
measurement range, air flows, detection or averaging time, as well as CPC model identification, shall be
stated in the measurement report. In addition, sampling equipment such as a buffer vessel or sampling
line shall be described. If the size distribution is known, it is recommended to estimate the diffusion loss
corrections.
9 Check of CPC performance
At the time of publication of this European Standard a calibration against the number concentration is
only possible with a reference instrument and a stable particle source of suitable particle size (see also
10.1). There is no primary standard for particle number concentration. Detailed description for the
calibration of CPCs is given in ISO 27891 [8].
NOTE A further possibly suitable method is described in [9].
A user can regularly check the performance of the CPC by comparing several CPCs together, or
comparing them with electrometers or differential mobility analysing systems by using a particle
source with particle size and concentration within the specified ranges given for all instruments
applied.
Recommendations of manufacturers should be taken into account.
At the time of publication, the manufacturers of CPCs use reference instruments (Faraday cup
electrometer or CPC) to set the count rate of the instruments they supply. An alternative recommended
way is to participate in round robin tests (see [10]) which are also commercially available [11]. For a
comparison of a CPC with an electrometer, see ISO 27891 [8] and EN ISO 28439 [21].
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10 Problems and uncertainties
10.1 CPC counting efficiency
In general, the detection efficiency will depend on the particle number concentration, the particle size,
and the particle composition. The particle sizes covered by the instruments range from approximately
2 nm to 3 µm.
For example, the CPC is characterized by a lower particle size d at which the counting efficiency is
50
50 %. Information from the manufacturer shall be taken into account and the applicable measurement
range shall be defined.
A typical example of the dependency of the counting efficiency on particle size is given in Figure 2. For
large particle sizes the efficiency reaches a plateau, which is near to 100 %. For example, the CPC is
characterized by a lower part
...
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