prEN 481

• Abstract:

  This document specifies sampling conventions for airborne particle size fractions to assess health-related exposure resulting from the inhalation of particles in workplace atmospheres. Conventions are defined for the inhalable, thoracic and respirable fractions. The sampling conventions only describe the inhalation of particles and their penetration in the respiratory tract as governed by inertia (impaction). Exhaled particles and deposition in the respiratory tract by other mechanisms, e.g. diffusion, are not considered in this document. The sampling conventions defined in this document apply to both indoor and outdoor workplaces. The conventions assume particles penetration and only oral breathing as a worst-case scenario. Nevertheless, the conventions are applicable to both oral and nasal breathing.; The conventions are defined based on assumptions given in Clause 6. The choice of convention for a specific application depends on the region of the respiratory tract affected by the health impact of the particle component of interest (see Clause 5). The conventions can be applied to various metrics, including particle number, length, surface area, volume, or mass, depending on the type of particle analysis performed on the sampled aerosol fraction. The health-related fraction concentrations defined in this document are often expressed as the mass of sampled particles per volume of sampled air to allow comparison with mass-based occupational exposure limit values.; The conventions primarily apply to the aforementioned metrics, however, they are not applicable to situations involving limit values expressed in a different metric, such as fibre limit values defined by length, diameter, and aspect ratio, unless a measurement procedure explicitly specifies sampling a particular health-related size fraction [11].; The primary objective of this document is to establish standardized conventions for health-related particle size fractions. Sampling is generally carried out using dedicated samplers, for which there is no need to measure the aerodynamic size distribution of the airborne particles to be sampled. Samplers separating airborne particles into one or more relevant fractions are currently available. In general, no assumptions or pre-knowledge are needed on the number of modes, modal diameter(s) or width of the particle aerodynamic size distribution of the airborne particles to be sampled.; The conventions in this document are intended to be used for the determination of the exposure of an average worker based on average penetration curves. This document is not intended to determine the deposited dose of an individual worker.; The conventions are primarily intended for assessing workers’ exposure to airborne particles by sampling the airborne particles. This document does not apply to large particles emitted at high speed that travel due to their initial momentum, instead of being carried by the air (airborne) and aspirated into humans’ respiratory tract and aerosol samplers by suction (see Annex B).; All wind speeds referenced throughout this document are based on the relative speed between the worker and the surrounding air.

• Status: Not Published
• Publication Date: 13-Jan-2027
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: CEN/TC 137 - Assessment of workplace exposure
• Drafting Committee: CEN/TC 137/WG 3 - Particulate matter
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 16-Jul-2026
• Completion Date: 16-Jul-2026
• Ref Project: oSIST prEN 481:2026 - Workplace exposure - Size fraction definitions for measurement of airborne particles

• Revises: EN 481:1993 - Workplace atmospheres - Size fraction definitions for measurement of airborne particles
• Effective Date: 04-Oct-2023

Overview

The prEN 481:2024 standard, developed by CEN, establishes size fraction definitions for measurement of airborne particles for workplace exposure assessment. This document supersedes the EN 481:1993 and provides updated sampling conventions for inhalable, thoracic, and respirable particle fractions. These conventions are essential for evaluating health-relevant exposure to airborne particles through inhalation in occupational settings.

This standard focuses on sampling airborne particles based on their aerodynamic diameter, considering impaction-driven penetration into the respiratory tract, and excludes other deposition mechanisms such as diffusion. The definitions apply to both indoor and outdoor workplaces and are designed to support occupational hygiene practices and compliance sampling.

Key Topics

• Sampling Conventions: prEN 481 defines conventions for three key particle size fractions relevant to worker health:

  • Inhalable fraction: Particles entering the respiratory tract through mouth and nose.
  • Thoracic fraction: Particles penetrating beyond the larynx into the thoracic region.
  • Respirable fraction: Particles depositing in the gas exchange region of the lungs (alveolar region).

• Particle Aerodynamic Diameter: Measurement and classification use the aerodynamic diameter, which relates to particle behavior during inhalation under airflow conditions.

• Health Exposure Assessment: The standard supports estimating health-relevant exposure by defining sampling efficiencies that approximate the fraction of airborne particles likely to deposit in various parts of the respiratory tract under typical breathing conditions.

• Applicability and Limitations:

  • Applies to airborne particles suspended in air, excluding particles propelled by momentum (particle projectiles).
  • Sampling conventions focus on impaction deposition only.
  • Not intended for individual dose assessment due to variability in deposition and clearance among workers.
  • Compatible with various particle metrics including mass, count, surface area, or volume depending on analysis methods.

• Sampler Design and Use: The document guides the use of samplers designed to selectively capture size fractions without measuring the complete aerodynamic size distribution, simplifying workplace monitoring.

Applications

• Occupational Hygiene: prEN 481 is crucial for assessing worker exposure to airborne particles and hazardous aerosols in various industrial environments such as manufacturing, construction, mining, and healthcare.

• Compliance Monitoring: Enables sampling aligned with health-related exposure limits, supporting compliance with mass-based occupational exposure limits (OELs).

• Risk Assessment: By using defined size fractions, occupational health professionals can better correlate measured particle concentrations with potential respiratory health risks.

• Air Quality Management: The conventions assist in measuring airborne particulates both indoors and outdoors, contributing to effective workplace air quality control.

• Sampler Development and Testing: Standard references provide a foundation for manufacturers and laboratories to develop and validate aerosol samplers consistent with size-selective sampling conventions.

Related Standards

• EN 1540:2021 – Terminology relating to workplace exposure, providing essential definitions referenced by prEN 481.

• CEN/TR 15230 – Guidance for sampling aerosol fractions defined in prEN 481.

• EN 13205 Series (Parts 1 to 6) – Performance testing standards for aerosol samplers used in workplace environments.

• EN 482 – General requirements and guidance for performance testing of occupational hygiene samplers, instruments, and analytical methods.

• EN 689 – Strategy for assessing compliance with occupational exposure limits, closely linked to measurement methods.

• EN ISO 13138 – Sampling conventions for respiratory tract deposition, complementing prEN 481 definitions on particle penetration.

Keywords

Workplace exposure, airborne particles, particle size fractions, inhalable fraction, thoracic fraction, respirable fraction, occupational hygiene, aerosol sampling, aerodynamic diameter, occupational exposure limits, particle inhalation, respiratory tract deposition, CEN standards, prEN 481.

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By adhering to prEN 481:2024, workplaces and occupational health professionals can ensure consistent, reliable measurement of airborne particles related to worker health risks, improving exposure assessment accuracy and supporting regulatory compliance efforts.

SLOVENSKI STANDARD
01-september-2026
Izpostavljenost na delovnem mestu - Definicije velikostnih razredov za merjenje
lebdečih delcev
Workplace exposure - Size fraction definitions for measurement of airborne particles
Arbeitsplatzatmosphäre - Feslegung der Größenfraktionen zur Messung luftgetragener
Partikel
Atmosphères des lieux de travail - Définition des fractions de taille pour le mesurage des
particules en suspension dans l'air
Ta slovenski standard je istoveten z: prEN 481
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2026
ICS 13.040.30 Will supersede EN 481:1993
English Version
Workplace exposure - Size fraction definitions for
measurement of airborne particles
Atmosphères des lieux de travail - Définition des Exposition am Arbeitsplatz - Festlegung der
fractions de taille pour le mesurage des particules en Größenfraktionen zur Messung luftgetragener Partikel
suspension dans l'air
This draft European Standard is submitted to CEN members for second enquiry. It has been drawn up by the Technical
Committee CEN/TC 137.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
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.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 481:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviated terms . 7
5 Principle of conventions . 8
6 Assumptions and approximations . 9
7 Specifications for conventions and corresponding fraction concentrations . 10
7.1 Conventions . 10
7.1.1 Inhalable sampling convention . 10
7.1.2 Thoracic sampling conventions . 15
7.1.3 Respirable sampling convention . 17
Annex A (informative) Main arguments for revision and significant technical changes . 19
Annex B (informative) Sampling situations for which the definitions of health-related
fractions are NOT directly applicable . 24
Annex C (informative) General information on particle inhalability and penetration,
and on sampling conventions . 26
Bibliography . 28

European foreword
This document (prEN 481:2026) 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 document is currently submitted to the 2nd CEN enquiry.
This document will supersede EN 481:1993.
The technical modifications in comparison with the previous edition are listed in Annex A.
Introduction
The proportion of total particulate matter that is inhaled into a human body depends on the aerodynamic
diameter of the particles, on the speed and direction of air movement near the body, on the breathing
rate of the individual, and whether breathing is through the nose or mouth. Inhaled particles can then
deposit somewhere in the respiratory tract or can be exhaled. The site and amount of deposition, and
probability of exhalation, depend on the aerodynamic diameter of the particle, respiratory tract anatomy,
breathing pattern, and other factors.
Tissues in the respiratory tract can absorb soluble components from deposited particles at any site of
deposition. Particles can cause health damage due to the constituents they carry which can be reactive,
either chemically or biologically, depending on their composition. Insoluble particles can be transported
to another part of the respiratory tract or body, where they can be taken up by cells and tissues and be
detrimental to health.
There is considerable inter-individual variability in particle inhalation and deposition probabilities.
Nevertheless, it is necessary to define conventions for size-selective sampling of airborne particles when
the purpose of sampling is health-related, such as for compliance testing.
This document defines the inhalable, thoracic, and respirable sampling conventions based on the
penetration probability of particles into the respiratory tract. The separation of particles from the inhaled
air by other mechanisms than impaction is disregarded in this document, because the transport of
particles with an aerodynamic diameter less than 0,5 µm do not primarily depend on inertia. For these
particles, the separation mechanism is instead mainly governed by diffusion, and the size of these
particles is best described by the particle diffusive (equivalent) diameter. The particle diffusive
(equivalent) diameter equals the diameter of a sphere with the same diffusion coefficient as the particle
under the prevailing conditions of temperature, pressure and relative humidity.
These conventions establish relationships between particle aerodynamic diameter and health-related
fractions, which approximate the quantity of particles penetrating specific regions of the respiratory tract
under average breathing conditions.
Measurements using sampling devices according to these conventions provide a more accurate
correlation between the measured concentration and the health risk compared to measurements of
undisturbed airborne particle size distribution. Relevant environmental conditions are stated in EN 689
[1].
Guidance for sampling the defined aerosol fractions is given in CEN/TR 15230 [2]. EN 13205-1 to −6 ([3]
to [8]) describe performance tests for candidate aerosol samplers for any of the sampling conventions
defined in this document. EN 482[9] outlines general performance requirements for samplers,
instruments, and analytical methods used in occupational hygiene. A strategy for testing compliance with
occupational exposure limits is given in EN 689 [1]. EN ISO 13138 [10] describes sampling conventions
for fractions deposited in regions of the respiratory tract.
1 Scope
This document specifies sampling conventions for airborne particle size fractions to assess health-related
exposure resulting from the inhalation of particles in workplace atmospheres. Conventions are defined
for the inhalable, thoracic and respirable fractions. The sampling conventions only describe the
inhalation of particles and their penetration in the respiratory tract as governed by inertia (impaction).
Exhaled particles and deposition in the respiratory tract by other mechanisms, e.g. diffusion, are not
considered in this document. The sampling conventions defined in this document apply to both indoor
and outdoor workplaces. The conventions assume particles penetration and only oral breathing as a
worst-case scenario. Nevertheless, the conventions are applicable to both oral and nasal breathing.
The conventions are defined based on assumptions given in Clause 6. The choice of convention for a
specific application depends on the region of the respiratory tract affected by the health impact of the
particle component of interest (see Clause 5). The conventions can be applied to various metrics,
including particle number, length, surface area, volume, or mass, depending on the type of particle
analysis performed on the sampled aerosol fraction. The health-related fraction concentrations defined
in this document are often expressed as the mass of sampled particles per volume of sampled air to allow
comparison with mass-based occupational exposure limit values.
The conventions primarily apply to the aforementioned metrics, however, they are not applicable to
situations involving limit values expressed in a different metric, such as fibre limit values defined by
length, diameter, and aspect ratio, unless a measurement procedure explicitly specifies sampling a
particular health-related size fraction [11].
The primary objective of this document is to establish standardized conventions for health-related
particle size fractions. Sampling is generally carried out using dedicated samplers, for which there is no
need to measure the aerodynamic size distribution of the airborne particles to be sampled. Samplers
separating airborne particles into one or more relevant fractions are currently available. In general, no
assumptions or pre-knowledge are needed on the number of modes, modal diameter(s) or width of the
particle aerodynamic size distribution of the airborne particles to be sampled.
The conventions in this document are intended to be used for the determination of the exposure of an
average worker based on average penetration curves. This document is not intended to determine the
deposited dose of an individual worker.
The conventions are primarily intended for assessing workers’ exposure to airborne particles
by sampling the airborne particles. This document does not apply to large particles emitted at high speed
that travel due to their initial momentum, instead of being carried by the air (airborne) and aspirated
into humans’ respiratory tract and aerosol samplers by suction (see Annex B).
All wind speeds referenced throughout this document are based on the relative speed between the
worker and the surrounding air.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
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.
NOTE The terms and definitions given in EN 1540 are reproduced here for improved readability.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
airborne particle
chemical or biological agent, in solid or liquid form, dispersed in air
Note 1 to entry: Smoke, fume, mist and fog consist of airborne particles.
Note 2 to entry: This term describes a class of particles with a specific property, namely those that are airborne
while being measured or sampled.
Note 3 to entry: Particle projectiles are a specific class of particles that move through air under its their own
momentum, which they obtained when they were ejected into air. A typical example is particles generated by using
grinding wheels. In order to be able to travel a long distance under its own momentum, a particle projectile needs
to be large (much larger than 100 µm) and have been emitted at high speeds (exceeding 5 m/s to 10 m/s). Once
drag has consumed all the original momentum of a particle projectile, it moves in the air as any other airborne
particle, under the influence of air currents, air suction, drag and external forces, e.g. gravity.
[SOURCE: EN 1540:2021, 3.1.1.5, modified — Notes 1 to 3 to entry have been added.]
3.2
alveolar region
compartment of the human respiratory tract consisting of respiratory bronchioles, alveolar ducts,
alveolar sacs and alveoli
Note 1 to entry: The American Conference of Governmental Industrial Hygienists uses the term Gas-Exchange
region and the (US) National Commission on Radiological Protection uses the term Pulmonary region [12].
3.3
inhalability
ratio of the concentration of particles entering the respiratory tract as a function of the aerodynamic
particle diameter to the corresponding concentration in the air before the particles are affected by the
presence of the exposed individual and inhalation (i.e., the undisturbed airborne particle size
distribution)
3.4
inhalable sampling convention
E
Ix,
sampling convention describing the probability of undisturbed particles entering the respiratory tract by
inhalation through the mouth as a function of the aerodynamic particle diameter for wind speed range x
3.5
particle aerodynamic diameter
d
ae
diameter of a sphere of 1 g/cm density with the same terminal settling velocity in calm air as the particle,
under the prevailing conditions of temperature, pressure and relative humidity
Note 1 to entry: The particle aerodynamic diameter is the diameter of an equivalent sphere that is used to
describe the mass based transport phenomena of a particle of arbitrary shape and density like inertia or
gravitational settling.
[SOURCE: EN 1540:2021, 3.1.2.11, modified — Note 1 to entry has been deleted and a new Note 1 has
been added.]
3.6
respirable penetration probability convention
e
R
convention describing the probability of inhaled particles penetrating to the alveolar region as a function
of the aerodynamic particle diameter
3.7
respirable sampling convention
E
R,x
sampling convention describing the probability of undisturbed particles penetrating to the alveolar
region as a function of the aerodynamic particle diameter for wind speed range x
3.8
sampling convention
the probability of the undisturbed airborne particles to be included in the health-related fraction in
question as a function of their aerodynamic diameter that defines the target specification for the sampling
efficiency of a sampling system for this fraction
3.9
thoracic penetration probability convention
e
T
convention describing the probability of inhaled particles penetrating beyond the larynx as a function of
the aerodynamic particle diameter
3.10
thoracic sampling convention
E
T,x
sampling convention describing the probability of undisturbed particles penetrating beyond the larynx
as a function of the aerodynamic particle diameter for wind speed range x
3.11
undisturbed airborne particle size distribution
size distribution of all airborne particles present in the air before the particles are affected by the
presence of the sampler, or in the case of a personal sampler (mounted on a mannequin/person) by the
presence of the mannequin/person
3.12
undisturbed particle
airborne particle before being disturbed by the presence of the sampler, or in the case of a personal
sampler (mounted on a mannequin/person) by the presence of the mannequin/person
4 Symbols and abbreviated terms
For the purposes of this document, the following symbols and abbreviations apply:
particle aerodynamic diameter
d
ae
median of the lognormal distribution expressing the definition of the
d
ae,R,p=0,50
respirable sampling convention
median of the lognormal distribution expressing the definition of the thoracic
d
ae,,T p=0,50
sampling convention
e respirable penetration probability convention
R
e thoracic penetration probability convention
T
E inhalable sampling convention
I
inhalable sampling convention for intermediate wind speed range
E
I, int
inhalable sampling convention in the low wind speed range
E
I, lwsr
inhalable sampling convention in the medium wind speed range
E
I, mwsr
respirable sampling convention in the low wind speed range
E
R,lwsr
respirable sampling convention in the medium wind speed range
E
R,mwsr
thoracic sampling convention in the low wind speed range

E
T,lwsr
thoracic sampling convention in the medium wind speed range
E
T,mwsr
geometric standard deviation of the lognormal distribution expressing the
GSD
T
definition of the thoracic sampling convention; GSD = 1,50
T
geometric standard deviation of the lognormal distribution expressing the
GSD
R
definition of the respirable sampling convention; = 1,50
GSD
R
is the cumulative lognormal distribution function with argument z

Φ z
( )
w wind speed
x is an index for the wind speed range; x can be lwsr, mwsr or int for low,
medium or intermediate medium wind speed range, respectively
z is the argument of the cumulative lognormal distribution function;
5 Principle of conventions
The sampling conventions are designed on the principle that only fractions of the undisturbed airborne
particle size distribution penetrate to different parts of the respiratory tract during breathing. These are
estimated by the inhalable, thoracic and respirable fractions. This document presents probability
functions approximating the inhalable fraction, the thoracic fraction (particles penetrating beyond the
larynx), and the respirable fraction (particles penetrating to the alveolar region). These curves are called
the inhalable sampling convention (see 3.4), the thoracic sampling convention (see 3.10) and the
respirable sampling convention (see 3.7), respectively.
Annex C provides background information for the derivation of the sampling conventions.
The conventions for the respirable and thoracic fractions are for the fraction that can penetrate to that
respective region of the respiratory tract. These conventions are considered to be penetration-based as
they represent the fraction of particles that penetrate to specific regions of the respiratory tract. The
conventions in this document are not suitable for the determination of the deposited dose. Conventions
for the deposited fraction in the extra-thoracic, tracheobronchial and alveolar regions are given in
EN ISO 13138 [10].
The sampling efficiency of an aerosol sampling system used for measurements of the inhalable, respirable
or thoracic fraction concentrations shall comply with the sampling convention appropriate to the region
of the respiratory tract where deposition of the substance being measured might lead to a negative health
effect. Compliance criteria are stated in the EN 13205 series ([3] to [7]). For example, the inhalable
sampling conventions can be applied when the substance may cause health effects regardless of the
deposition site. The thoracic sampling convention is used when the substance targets regions beyond the
larynx, such as the bronchi, and the respirable sampling convention is used when the substance primarily
affects the alveolar region.
The measured concentration is a property of the air quality at the point of the measurement. Due to the
large individual differences in the breathing patterns and the individual variability of the respiratory
tract, the measured concentration can only be a proxy for what an individual worker is actually exposed
to.
6 Assumptions and approximations
The definition of sampling conventions requires approximations and assumptions to represent the
complex processes, that govern how particles enter and penetrate to different parts of the respiratory
tract. In part this is due to the lack or variability of experimental data.
The conventions are only approximations to particle behaviour. E.g. the inhalability and penetration of
airborne particles to the different regions of the respiratory tract depend on the movement of air relative
to the worker (speed and direction), worker’s breathing rate and whether breathing occurs through the
nose or mouth, all of which vary between individuals.
The following assumptions and approximations are particularly important (see Annex C):
— The conventions assume a representative value of breathing rate, and are not taking into account
individual variability;
— The conventions assume only oral breathing as a worst case scenario;
NOTE Nasal aspiration efficiency in literature is very diverse, but shows a tendency to be lower than the oral
aspiration efficiency [13, 14, 15].
— The inhalable sampling conventions assume two workplace wind speed ranges: low wind speed
(<0,2 m/s) and medium wind speed (0,5–4 m/s). The probability functions for each wind speed
range are approximated by respective formulas, which are substantiated by experimental data. A
probability function for the intermediate wind speed range (0,2 – 0,5 m/s) is derived from linear
interpolation. Wind speeds > 4 m/s are out of the scope of this document;
— The conventions assume an individual to be evenly exposed to all wind directions;
— The conventions provide an approximation of average penetration to the relevant regions of the
respiratory tract as a function of the aerodynamic particle diameter;
— Particles with aerodynamic diameters below 0,5 µm are assumed to ideally follow airflows and
consequently, their inhalability is assumed to be 1. Although this assumption might not hold
completely for very small particles with sizes below approximately 0,05 µm due to particle diffusion,
the effect is neglected, since these small particles usually only have negligible contributions to the
thoracic and inhalable mass concentration. If the inhalable or thoracic particle number concentration
is determined, this assumption can lead to an overestimation;
— Particles with aerodynamic diameters larger than 100 µm are excluded from the convention, because
there is too little experimental data to derive values for the inhalable conventions.
7 Specifications for conventions and corresponding fraction concentrations
7.1 Conventions
7.1.1 Inhalable sampling convention
7.1.1.1 General
The probability for a particle to be inhaled depends on the relative wind speed between the worker and
the surrounding air (w), apart from the major dependence on d . In the low wind speed range, this
ae
inhalability is high and almost independent of w. In the medium wind speed range, the inhalability
decreases but levels out from w ≈ 0,5 m/s, and it is approximately constant up to w ≈ 4 m/s.
Two definitions have been established based on experimental data for the low and medium wind speed
range. A third definition for the transition between the low and medium wind speed range has been
established as a linear interpolation between the two.
NOTE The experimentally substantiated low and medium wind speed range cover the wind speeds of ≤ 0,1 m/s
and 1 m/s, prescribed for the testing of samplers of the inhalable fraction according to EN 13205-2.
7.1.1.2 Inhalable sampling convention in low wind speed range
Sampling of the inhalable fraction in the low wind speed range (w ≤ 0,2 m/s) shall conform to the
following convention: the fraction E of the undisturbed airborne particle concentration,
I, lwsr
at an aerodynamic diameter d that is to be sampled, shall be calculated by:
ae
E 1+ ad (1)
I, lwsr 1 ae
where
E is the inhalable sampling convention in the low wind speed range;
I, lwsr
is the particle aerodynamic diameter with 0,5 µm ≤ ≤ 100 µm, in micrometres (µm);
d d
ae ae
is a constant with a value of – 0,0038 /µm.
a
Some values for these two formulas are given in Table 1 and illustrated in Figure 1.
Formula (1) is only valid in the size range stated, i.e. 0,5 µm ≤ d ≤ 100 µm. Sufficient experimental data
ae
on the inhalable fraction do not yet exist for d > 100 µm, therefore larger particles are not included in
ae
the convention. For d < 0,5 um the inhalability can be assumed to be 1.
ae
Formula (1) shall not be extrapolated for d > 100 µm.
ae
7.1.1.3 Inhalable sampling convention in medium wind speed range
Sampling of the inhalable fraction in the medium wind speed range (0,5 m/s < w ≤ 4 m/s) shall conform
to the following convention: the fraction E of the total airborne particle concentration, at an
I, mwsr
aerodynamic diameter d that is to be sampled, shall be calculated by:
ae
when d < 4,485 µm:
ae
E d 1+ b d (2)
( )
I,mwsr ae 1 ae
=
=
when d ≥ 4,485 µm:
ae
 
d
ae
  (3)
E d cc+ ln
( )
I ,mwsr ae 0 1
 
µm
 
where
E is the inhalable sampling convention in the medium wind speed range;
I, mwsr
d is the particle aerodynamic diameter with 0,5 µm ≤ d ≤ 100 µm, in micrometres (µm);
ae ae
b is a constant with a value of – 0,0038 /µm;
c is a constant with a value of 1,289;
c is a constant with a value of – 0,204.
Formulae (2) and (3) are only valid in the size ranges stated. Sufficient experimental data on the inhalable
fraction do not yet exist for d > 100 µm, therefore larger particles are not included in the convention.
ae
For d < 0,5 um the inhalability can be assumed to be 1.
ae
Formula (3) shall not be extrapolated for d > 100 µm.
ae
Some values for these two formulas are given in Table 1 and illustrated in Figure 1.
Table 1 — Numerical values of the sampling conventions at low wind speed
and medium wind speed (as fractions of the undisturbed airborne particle size distribution)
Particle Sampling conventions Sampling conventions
aerodyna at low wind speed at medium wind speed
mic (w ≤ 0,2 m/s) (0,5 m/s < w ≤ 4 m/s)
diameter
dae inhalable thoracic respirable inhalable thoracic respirable
µm
E E E E E E
I,lwsr T,lwsr R,lwsr I,mwsr T,mwsr R,mwsr
< 0,5 1,000 1,000 1,000 1,000 1,000 1,000
0,5 0,998 0,998 0,998 0,998 0,998 0,998
1 0,996 0,996 0,996 0,996 0,996 0,996
2 0,992 0,992 0,951 0,992 0,992 0,951
3 0,989 0,987 0,758 0,989 0,987 0,758
4 0,985 0,974 0,500 0,985 0,974 0,500
5 0,981 0,942 0,292 0,961 0,923 0,286
6 0,977 0,884 0,160 0,923 0,836 0,151
7 0,973 0,802 0,084 0,892 0,735 0,077
8 0,970 0,704 0,044 0,865 0,628 0,039
9 0,966 0,600 0,023 0,841 0,523 0,020
10 0,962 0,500 0,012 0,819 0,426 0,010
11 0,958 0,409 0,006 0,800 0,341 0,005
=
Particle Sampling conventions Sampling conventions
aerodyna at low wind speed at medium wind speed
mic (w ≤ 0,2 m/s) (0,5 m/s < w ≤ 4 m/s)
diameter
dae inhalable thoracic respirable inhalable thoracic respirable
µm
E E E E E E
I,lwsr T,lwsr R,lwsr I,mwsr T,mwsr R,mwsr
12 0,954 0,329 0,003 0,782 0,269 0,003
13 0,951 0,261 0,002 0,766 0,211 0,001
14 0,947 0,206 0,001 0,751 0,163 0,001
15 0,943 0,161 0,001 0,737 0,126 0,001
16 0,939 0,125 0,000 0,723 0,097 0,000
18 0,932 0,075 0,000 0,699 0,056 0,000
20 0,924 0,045 0,000 0,678 0,033 0,000
25 0,905 0,012 0,000 0,632 0,009 0,000
30 0,886 0,003 0,000 0,595 0,002 0,000
35 0,867 0,001 0,000 0,564 0,001 0,000
40 0,848 0,000 0,000 0,536 0,000 0,000
50 0,810 0,000 0,000 0,491 0,000 0,000
60 0,772 0,000 0,000 0,454 0,000 0,000
80 0,696 0,000 0,000 0,395 0,000 0,000
100 0,620 0,000 0,000 0,350 0,000 0,000
Key
X aerodynamic diameter dae in µm
Y sampling convention
1 inhalable low wind speed range Ei, lwsr
2 inhalable medium wind speed range Ei, mwsr
3 thoracic low wind speed range ET, lwsr
4 thoracic medium wind speed range ET, mwsr
5 respirable low wind speed range ER, lwsr
6 respirable medium wind speed range ER, mwsr
Figure 1 — Sampling conventions for the inhalable, thoracic and respirable fraction
(in low and medium wind speed ranges)
7.1.1.4 Inhalable sampling convention in wind speed range 0,2 m/s < w ≤ 0,5 m/s
Due to the scarcity of data for the wind speed range from 0,2 m/s to 0,5 m/s, it is currently not possible
to derive an inhalable sampling convention based on experimental data. Instead, Formula (4), in
conjunction with Formulae (5) and (6) provides a pragmatic solution for a mathematical description of
the transition for wind speeds between 0,2 m/s and 0,5 m/s, i.e. between the low and medium wind speed
range (see Figure 2).
The proposed solution is based on the assumption that Formula (1) is appropriate for the inhalable
sampling convention for wind speeds w ≤ 0,2 m/s and Formulae (2) and 3, respectively, for
0,5 m/s < w ≤ 4 m/s and that the inhalability changes linearly from Formula (1) to Formula (2) or 3,
respectively, for wind speeds in the intermediate range.
For intermediate range of 0,2 m/s < w ≤ 0,5 m/s, the inhalable sampling convention E shall be
I, int
approximated by a linear interpolation, using two wind speed dependent transition parameters α(w) and
β(w):
E w=α wE× +×β wE (4)
( ) ( ) ( )
I, int I,,lwsr I mwsr
with
α w =− g× w+ h (5)
( )
and
(6)
β w= g×−w i
( )
where
E is the inhalable sampling convention for intermediate wind speed range;
I, int
E is the inhalable sampling convention in the low wind speed range;
I,lwsr
E is the inhalable sampling convention in the medium wind speed range;
I,mwsr
w is the wind speed;
αβ,  are wind speed dependent transition parameters;
g is the slope of the transition parameters with a value of 3,3333 s/m;
h is a constant with a value of 1,6667;
is a constant with a value of 0,6667.
i
For wind speeds w≤ 02, ms/ , α =1 and β = 0, for w> 0,5 ms/ , α =0 and β =1.
For particle sizes d ≥ 4,485 µm Formula (2) shall be used for E and Formula (3) for d < 4,485 µm.
ae I, mwsr ae
The inhalable sampling conventions for the low wind speed range, medium wind speed range and for
three exemplary wind speeds in the intermediate wind speed range are shown in Figure 2.
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