SIST EN ISO 28439:2011
(Main)Workplace atmospheres - Characterization of ultrafine aerosols/nanoaerosols - Determination of the size distribution and number concentration using differential electrical mobility analysing systems (ISO 28439:2011)
Workplace atmospheres - Characterization of ultrafine aerosols/nanoaerosols - Determination of the size distribution and number concentration using differential electrical mobility analysing systems (ISO 28439:2011)
This document specifies the determination of the size distribution and number concentration of ultrafine aerosols and nanoaerosols using mobility particle sizers (also called differential mobility analysers). It provides a sampling guideline for occupational hygienists and researchers to effectively characterise and monitor ultrafine aerosol and nanoaerosol exposures in the workplace.
Arbeitsplatzatmosphäre - Charakterisierung ultrafeiner Aerosole/Nanoaerosole - Bestimmung der Größenverteilung und Anzahlkonzentration mit differentiellen elektrischen Mobilitätsanalysesystemen (ISO 28439:2011)
Dieses Dokument gibt einen Leitfaden zur Bestimmung der Anzahlkonzentration und Größenverteilung ultrafeiner Aerosole und Nanoaerosole mit Mobilitäts-Partikelsichtern (auch Differential-Mobilitätsanalyser genannt). Bei ultrafeinen Aerosolen und Nanoaerosolen sind Expositionsmaße wie die Anzahl- und Ober-flächenkonzentration von Bedeutung. Dieses Dokument hilft bei der Beurteilung der Exposition gegenüber ultrafeinen Aerosolen und Nanoaerosolen am Arbeitsplatz.
Insbesondere wird das differentielle elektrische Mobilitäts-Spektrometer (DEMC) erörtert, dass jetzt von mehreren Anbietern zur Verfügung gestellt wird. Behandelt werden die Grundsätze der Handhabung, Proble¬me bei der Probenahme in der Arbeitsplatzumgebung, Kalibrierung, Wartung der Ausrüstung, Messunsicher¬heit und die Angabe der Messergebnisse.
Air des lieux de travail - Caractérisation des aérosols ultrafins/nanoaérosols - Détermination de la distribution granulométrique et de la concentration en nombre à l'aide de systèmes d'analyse différentielle de mobilité électrique (ISO 28439:2011)
L'ISO 28439:2011 fournit des lignes directrices permettant de déterminer la concentration en nombre et la distribution granulométrique d'aérosols ultrafins et de nanoaérosols au moyen de spectromètres de mobilité électrique (également appelés analyseurs différentiels de mobilité). Seule la fraction de particules de l'aérosol est considérée. Pour des aérosols ultrafins et des nanoaérosols, des métriques d'exposition telles que la concentration en nombre et en surface sont très importantes.
L'ISO 28439:2011 fournit également des lignes directrices pour la détermination de l'exposition aux aérosols ultrafins et aux nanoaérosols sur le lieu de travail.
En particulier, le système d'analyse différentielle de mobilité (DMAS), désormais disponible auprès de plusieurs distributeurs, est présenté. Les principes de fonctionnement, les problèmes d'échantillonnage dans l'environnement du lieu de travail, l'étalonnage, l'entretien du matériel, l'incertitude de mesure, et le rapport des résultats de mesurage sont couverts.
Des problèmes potentiels et des limitations sont décrits, qui nécessitent d'être abordés quand des valeurs limites sont fixées et que des mesurages de conformité sont effectués.
Zrak na delovnem mestu - Karakterizacija ultrafinih aerosolov/nanoaerosolov - Določevanje porazdelitve velikosti in številčne koncentracije z uporabo analiznih sistemov za diferenčno mobilnost (ISO 28439:2011)
Ta dokument opredeljuje določevanje porazdelitve velikosti in številčne koncentracije ultrafinih aerosolov in nanoaerosolov z uporabo mobilnostnih merilnikov velikosti delcev (imenovanih tudi sistemi za diferenčno mobilnost). Podaja vodilo za vzorčenje za poklicne higienike in raziskovalce za učinkovito karakterizacijo in nadzor izpostavljenosti ultrafinim aerosolom in nanoaerosolom na delovnem mestu.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 28439:2011
01-december-2011
=UDNQDGHORYQHPPHVWX.DUDNWHUL]DFLMDXOWUDILQLKDHURVRORYQDQRDHURVRORY
'RORþHYDQMHSRUD]GHOLWYHYHOLNRVWLLQãWHYLOþQHNRQFHQWUDFLMH]XSRUDERDQDOL]QLK
VLVWHPRY]DGLIHUHQþQRPRELOQRVW ,62
Workplace atmospheres - Characterization of ultrafine aerosols/nanoaerosols -
Determination of the size distribution and number concentration using differential
electrical mobility analysing systems (ISO 28439:2011)
Arbeitsplatzatmosphäre - Charakterisierung ultrafeiner Aerosole/Nanoaerosole -
Bestimmung der Größenverteilung und Anzahlkonzentration mit differentiellen
elektrischen Mobilitätsanalysesystemen (ISO 28439:2011)
Air des lieux de travail - Caractérisation des aérosols ultrafins/nanoaérosols -
Détermination de la distribution granulométrique et de la concentration en nombre à
l'aide de systèmes d'analyse différentielle de mobilité électrique (ISO 28439:2011)
Ta slovenski standard je istoveten z: EN ISO 28439:2011
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
SIST EN ISO 28439:2011 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 28439:2011
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SIST EN ISO 28439:2011
EUROPEAN STANDARD
EN ISO 28439
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2011
ICS 13.040.30
English Version
Workplace atmospheres - Characterization of ultrafine
aerosols/nanoaerosols - Determination of the size distribution
and number concentration using differential electrical mobility
analysing systems (ISO 28439:2011)
Air des lieux de travail - Caractérisation des aérosols Arbeitsplatzatmosphäre - Charakterisierung ultrafeiner
ultrafins/nanoaérosols - Détermination de la distribution
Aerosole/Nanoaerosole - Bestimmung der
granulométrique et de la concentration en nombre à l'aide Größenverteilung und Anzahlkonzentration mit
de systèmes d'analyse différentielle de mobilité électrique differentiellen elektrischen Mobilitätsanalysesystemen (ISO
(ISO 28439:2011) 28439:2011)
This European Standard was approved by CEN on 10 March 2011.
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, 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
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 28439:2011: E
worldwide for CEN national Members.
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SIST EN ISO 28439:2011
EN ISO 28439:2011 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 28439:2011
EN ISO 28439:2011 (E)
Foreword
This document (EN ISO 28439:2011) 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, in
collaboration with Technical Committee ISO/TC 146 "Air quality".
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 October 2011, and conflicting national standards shall be withdrawn at
the latest by October 2011.
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.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
3
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SIST EN ISO 28439:2011
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SIST EN ISO 28439:2011
INTERNATIONAL ISO
STANDARD 28439
First edition
2011-04-01
Workplace atmospheres —
Characterization of ultrafine aerosols/
nanoaerosols — Determination of the size
distribution and number concentration
using differential electrical mobility
analysing systems
Air des lieux de travail — Caractérisation des aérosols ultrafins/
nanoaérosols — Détermination de la distribution granulométrique et de
la concentration en nombre à l'aide de systèmes d'analyse différentielle
de mobilité électrique
Reference number
ISO 28439:2011(E)
©
ISO 2011
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
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ii © ISO 2011 – All rights reserved
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Symbols and abbreviated terms .2
4.1 Symbols.2
4.2 Abbreviated terms.3
5 Principle .3
6 Equipment .4
6.1 General .4
6.2 Sampling line .4
6.3 Pre-separator .5
6.4 Particle charge conditioner .5
6.5 DEMC .5
6.6 Aerosol particle detector .5
7 Measurement strategy .6
8 Measuring procedure.6
8.1 Preparation.6
8.2 Sampling .7
9 Presentation and evaluation of data.7
10 Check of DMAS performance.8
10.1 Check on particle classification.8
10.2 Check on particle number-counting efficiency .8
11 Problems and errors .8
11.1 CPC (CNC) counting efficiency.8
11.2 Particles with multiple charges.9
11.3 Sampling losses .9
11.4 Uncertainties.10
11.5 Overloading.11
11.6 Sampling of fibres .11
11.7 Humidity .11
11.8 Maintenance.11
Annex A (informative) Methods for determining exposure .12
Annex B (informative) List of manufacturers (non-comprehensive).13
Bibliography.14
© ISO 2011 – All rights reserved iii
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
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 2.
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 28439 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 137, Assessment of workplace exposure to chemical and biological agents, in collaboration with
Technical Committee ISO/TC 146, Air quality, Subcommittee SC 2, Workplace atmospheres, in accordance
with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
iv © ISO 2011 – All rights reserved
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
Introduction
Within occupational hygiene, aerosol concentrations have been traditionally measured in terms of mass
concentrations. For some ultrafine aerosols and nanoaerosols, other exposure metrics such as the number
and surface area concentration are likely to become important for predicting health effects, depending on
chemical and physical properties. This International Standard provides a method for determining the number
concentration and size distribution of ultrafine aerosols and nanoaerosols at workplaces by using differential
mobility analysing systems (DMASs). This can be used by occupational hygienists and researchers to
measure the concentration at some workplaces. The system is generally not suitable for personal exposure
measurements.
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SIST EN ISO 28439:2011
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SIST EN ISO 28439:2011
INTERNATIONAL STANDARD ISO 28439:2011(E)
Workplace atmospheres — Characterization of ultrafine
aerosols/nanoaerosols — Determination of the size distribution
and number concentration using differential electrical mobility
analysing systems
1 Scope
This International Standard provides guidelines for the determination of the number concentration and size
distribution of ultrafine aerosols and nanoaerosols by use of mobility particle sizers (also called differential
mobility analysers). Only the particle fraction of the aerosol is considered. For ultrafine aerosols and
nanoaerosols, exposure metrics such as the number and surface area concentration are important.
This International Standard also gives guidelines for the determination of workplace exposure to ultrafine
aerosols and nanoaerosols.
Specifically, the differential mobility analysing system (DMAS), now available from several vendors, is
discussed. 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, which need to be addressed when limit values are fixed and
compliance measurements carried out.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/TR 27628, Workplace atmospheres — Ultrafine, nanoparticle and nano-structured aerosols — Inhalation
exposure characterization and assessment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TR 27628 and the following apply.
3.1
critical electrical mobility
Z
crit
electrical mobility of particles that in the differential electrical mobility classifier are transferred from the sample
air flow to the exiting monodisperse aerosol flow
NOTE Due to the finiteness of the DEMC, the exiting monodisperse flow is not strictly monodisperse, but
corresponds to a range of electrical mobilities for each voltage.
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
3.2
particle charge equilibrium
charging condition for aerosol particles that is stable after exposure to positive and negative ions for a
sufficiently long period of time
NOTE 1 Bipolar ions are produced by either a radioactive source or a corona discharge.
NOTE 2 The electrical charge on individual particles of an aerosol at charge equilibrium is not neutral.
[1]
NOTE 3 Adapted from ISO 15900:2009 , 2.11.
3.3
(equivalent) particle electrical mobility diameter
diameter of a sphere with the same electrical mobility as the particle in question
4 Symbols and abbreviated terms
4.1 Symbols
B particle mechanical mobility s/kg
C Cunningham correction factor 1
3
C aerosol number concentration 1/m
N
d particle diameter nm
d equivalent particle electrical mobility diameter m
p
d average equivalent particle electrical mobility diameter m
p
2
D particle diffusion coefficient m /s
−19
e basic unit of charge (elementary charge) 1,602 177 × 10 C
3
q DEMC sample air flow rate m /s
1
3
q DEMC filtered sheath air flow rate m /s
2
3
q DEMC excess air flow rate m /s
3
3
q DEMC exiting air flow rate to particle detector m /s
4
−23
k Boltzmann constant 1,38 × 10 N⋅m/K
L length of sampling line m
n number of charges 1
p penetration through sampling line 1
t (coagulation) time s
t scan time s
scan
T absolute temperature at which the DEMC is operated K
3
V volume of buffer vessel for the sample air flow rate m
v
2
Z electrical mobility of a charged airborne particle m /V⋅s
2
Z critical electrical mobility of a charged airborne particle m /V⋅s
crit
η gas viscosity Pa⋅s
μ parameter for diffusion losses 1
2 © ISO 2011 – All rights reserved
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
4.2 Abbreviated terms
CNC condensation nuclei counter
CPC condensation particle counter
DEMC differential electrical mobility classifier
DMAS differential mobility analysing system
NOTE A DMAS is also known as a differential mobility particle sizer (DMPS) or scanning mobility particle sizer (SMPS).
HEPA high efficiency particle arrestor
5 Principle
The aerosol is sampled in the workplace at a position representative of the atmosphere to which a worker
might be exposed. Larger particles than approximately 1 µm are precipitated and the particles smaller than
approximately 1 µm drawn into the instrument. After charge conditioning, the aerosol particles are separated
in the electrical field of the DEMC (see References [6] and [7]) according to their electrical mobility, which is
given by Equation (1).
Zn= eB ⎫
⎪
C (1)
⎬
B =
⎪
3πηd
p
⎭
where
Z is the electrical mobility, in metres squared per volt second, of a charged aerosol particle;
n is the number of electrical charges;
−19
e is the basic unit of charge (elementary charge), 1,602 177 × 10 C;
B is the particle mechanical mobility, in seconds per kilogram;
C is the Cunningham correction factor;
η is the gas viscosity, in pascal seconds;
d is the equivalent particle electrical mobility diameter, in metres.
p
The critical particle electrical mobility, Z , is directly related to the geometric dimensions of the DEMC. The
crit
equivalent particle electrical mobility diameter, d , can be determined from equations provided by the
p
instrument manufacturer.
Particles of a certain size or size interval are counted in a condensation nuclei counter (CNC) [also known as
a condensation particle counter (CPC)] or electrometer, and the particle number concentration for each size or
size interval is determined. By scanning or stepwise changing the voltage of the DEMC, a number size
distribution is obtained. The size range from 3 nm to 1 000 nm in electrical mobility diameter can be partly
covered by different instruments (see Reference [8]). The DEMC has the advantage that the electrical mobility
diameter is approximately equivalent to the projected-area diameter of particles (defined as the diameter of a
sphere with the same projected area as the particles being sized) with compact geometries. The entire
number concentration is obtained by adding or integrating all size channels.
Though the composition of the sampled particles cannot be obtained, the distribution of surface area and
volume concentration in some instances, e.g. if the particles are known to be spherical, can be estimated from
calculations provided by the manufacturer or in the literature.
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
6 Equipment
6.1 General
A DMAS consists of different instrument sections (see Figure 1):
a) pre-separator;
b) particle charger or particle charge conditioner;
c) differential electrical mobility classifier (DEMC), with flow control and high voltage control;
d) particle detector;
e) system controller, with data acquisition and data analysis (typically built-in firmware or dedicated software
on a personal computer).
Figure 1 — Major parts of a DMAS
6.2 Sampling line
The aerosol is often sampled with a flexible tube in order to access the breathing zone of a worker. The
material of the tube shall be an electrical conductor. Particle diffusion losses should be minimized. This can be
accomplished by using tubes of short length. For example, the application of flexible rubber tubes of
conducting material of length up to a few metres with an inner diameter of 4 mm or 6 mm ensures a short
residence time in the tube (see 11.3.2). The flow in the sampling line shall be laminar.
When sampling highly fluctuating aerosols like welding fumes it is recommended additionally that a buffer
vessel be used in order to average the concentration during the scan. The buffer vessel shall be electrically
conducting and be earthed. The mean residence time of the buffer vessel shall be related to the scan time. In
order to get a relatively stable concentration over the scan time, the volume of the vessel can be chosen in
relation to the sample air flow rate according to Condition (2).
V
v
W 5 (2)
qt
1scan
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
where
V is the volume, in metres cubed, of the buffer vessel for the sample air flow rate;
v
q is the DEMC sample air flow rate, in metres cubed per second;
1
t is the scan time, in seconds.
scan
−5 3
EXAMPLE For a sample air flow rate of 0,3 l/min (0,5 × 10 m /s) and a scan time of 2 min (120 s), a vessel of 3 l
−3 3
(3 × 10 m ) is appropriate.
Smaller buffer volumes are preferred if the aerosol agglomerates by coagulation (high concentration of
primary particles) (see 11.3.3).
NOTE The state of knowledge at the time of publication allows no recommendation for an upper volume to be made.
6.3 Pre-separator
A pre-separator is required such that large particles above the desired measurement range are precipitated.
This can be done, for example, by use of a suitable impactor or cyclone. The pre-separator shall be cleaned
and, if necessary, greased regularly.
6.4 Particle charge conditioner
The aerosol is charged with free electrical charges by collisions with gas ions and electrons. The free
electrical charges are usually produced by a radioactive source in the air stream, separated by a thin
85 210 241
enclosure. Sources like Kr, Po or Am are used. The entire aerosol reaches a charge equilibrium of
known distribution (see Reference [9]).
NOTE The charging of non-spherical particles differs from that of spheres. Therefore the distribution of electrical
charges as a function of particle size employed in the inversion of the critical electrical mobility into a particle size interval
is strictly valid only for spherical particles.
6.5 DEMC
The conditioned aerosol reaches the electrical mobility classification section. A common DEMC comprises an
inner and an outer electrode maintained at an electrical potential difference typically between 20 V and
10 000 V (see Figure 2).
The particles are transported in laminar flow along an annular region or tube along with a clean air sheath.
The motion of the charged particles depends on their different mobilities, causing them to reach the electrode
at different positions. Particles of a narrow electrical mobility range centred on the critical electrical mobility are
sampled via a slit towards the end of the annular region and transported into the detection section.
6.6 Aerosol particle detector
The separated aerosol with the specified, critical, electrical mobility is led to a counter which determines the
number of particles per unit volume. The most widely used counter is the CPC (CNC). In this device, the
aerosol is brought into contact with supersaturated vapour (alcohol or water) which condenses on to the
particles. The particles grow rapidly to large droplets, typically several micrometres in diameter, and can then
be detected using optical methods. Another detector is the electrometer, which determines the net electrical
current provided by the sampled particles.
After passing through the detector, further analysis of the particles is not possible. Additional samplers
operated in parallel to the DMAS can be used to collect samples for further analysis, e.g. an electrostatic or
thermal precipitator.
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
Key
q DEMC sample air flow rate
1
q DEMC filtered sheath air flow rate
2
q DEMC excess air flow rate
3
q DEMC exiting air flow rate to particle detector
4
Z electrical mobility of a charged airborne particle
Z critical electrical mobility of a charged airborne particle
crit
Figure 2 — Scheme of a DMAS
7 Measurement strategy
The DMAS gives detailed information on the aerosol size distribution within a defined range. The DMAS can
be used to detect particle-emitting sources in the workplace, or measurements in the breathing zone of a
worker may be carried out to get information on personal exposure. Since DMAS instruments available at the
time of publication can only be used as static samplers, if possible a representative sampling position should
be found with the use of tubes, as specified in 6.2. Workplace air flow pattern characteristics, e.g. direction of
air flow relative to source and sampling position, and the presence of multiple sources are essential for either
selection of a sampling position or interpretation for worker exposure.
For workers moving around, a more structured sampling strategy is necessary (see Annex A).
NOTE For some workplace conditions, it is not possible to find a representative sampling location. In these cases,
the values of the measured data are less reliable.
[2]
General information about measurement strategy in workplaces can be found in EN 689 .
8 Measuring procedure
8.1 Preparation
The response of a DMAS shall be checked regularly, e.g. before and after a series of measurements, against
particle size standards (see 10.1).
Before performing a series of measurements, a zero check of the DMAS is useful by applying high efficiency
particle arrestor (HEPA) filters to both the sampling line and the sheath air.
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SIST EN ISO 28439:2011
ISO 28439:2011(E)
8.2 Sampling
If worker exposure is to be estimated, the aerosol shall be sampled in the breathin
...
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