Bsi bs en 13528 3 2003 (2008)

BRITISH STANDARD

BS EN
13528-3:2003

Ambient air quality —
Diffusive samplers for
the determination of
concentrations of gases
and vapours —
Requirements and test
methods —
Part 3: Guide to selection, use and
maintenance

The European Standard EN 13528-3:2003 has the status of a
British Standard

ICS 13.040.20

12&23<,1*:,7+287%6,3(50,66,21(;&(37$63(50,77('%<&23<5,*+7/$:

Confirmed
February 2008


BS EN 13528-3:2003

National foreword
This British Standard is the official English language version of
EN 13528-3:2003.

The UK participation in its preparation was entrusted by Technical Committee
EH/2, Air quality, to Subcommittee EH/2/3, Ambient atmospheres, which has
the responsibility to:
—

aid enquirers to understand the text;

—

present to the responsible international/European committee any
enquiries on the interpretation, or proposals for change, and keep the
UK interests informed;

—

monitor related international and European developments and
promulgate them in the UK.

A list of organizations represented on this subcommittee can be obtained on
request to its secretary.
Cross-references
The British Standards which implement international or European
publications referred to in this document may be found in the BSI Catalogue
under the section entitled “International Standards Correspondence Index”, or
by using the “Search” facility of the BSI Electronic Catalogue or of British
Standards Online.
This publication does not purport to include all the necessary provisions of a
contract. Users are responsible for its correct application.
Compliance with a British Standard does not of itself confer immunity
from legal obligations.

This British Standard, was
published under the authority
of the Standards Policy and
Strategy Committee on
23 December 2003

Summary of pages
This document comprises a front cover, an inside front cover, the EN title page,
pages 2 to 40, an inside back cover and a back cover.
The BSI copyright notice displayed in this document indicates when the
document was last issued.

Amendments issued since publication
Amd. No.
© BSI 23 December 2003

ISBN 0 580 43131 2

Date

Comments


EUROPEAN STANDARD

EN 13528-3

NORME EUROPÉENNE
EUROPÄISCHE NORM

December 2003

ICS 13.040.20

English version

Ambient air quality - Diffusive samplers for the determination of
concentrations of gases and vapours - Requirements and test
methods - Part 3: Guide to selection, use and maintenance
Qualité de l'air - Echantillonneurs par diffusion pour la
détermination de concentration des gaz et vapeurs Exigences et méthodes d'essai - Partie 3: Guide pour la
sélection, l'utilisation et la maintenance

Außenluftqualität - Passivsammler zur Bestimmung der
Konzentrationen von Gasen und Dämpfen - Teil 3:Anleitung
zur Auswahl, Andwendung und Handhabung

This European Standard was approved by CEN on 3 November 2003.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36

© 2003 CEN

All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members.

B-1050 Brussels

Ref. No. EN 13528-3:2003 E


EN 13528-3:2003 (E)

Contents

page

Foreword......................................................................................................................................................................4
Introduction .................................................................................................................................................................5
1

Scope ..............................................................................................................................................................6

2

Normative references ....................................................................................................................................6

3

Terms and definitions....................................................................................................................................6

4

Symbols and abbreviations ..........................................................................................................................7

5
5.1
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.2
5.2.1
5.2.2
5.2.3
5.3

Measurement objectives and strategy.........................................................................................................8
Measurements in support of Community Policy ........................................................................................8
Air Quality Directives.....................................................................................................................................8
Source-related assessment ..........................................................................................................................9
Forest Protection directives .......................................................................................................................10
Protection of ecosystems ...........................................................................................................................10
Public awareness .........................................................................................................................................10
Measurement in support of other policies ................................................................................................10

Measurement in support of national, regional or local policies .............................................................10
Protection of special ecosystems ..............................................................................................................10
Particular research aspects ........................................................................................................................10
Measurement strategy.................................................................................................................................11

6
6.1
6.2
6.3
6.4

Selection of the device ................................................................................................................................11
Sources of information................................................................................................................................11
Selection of a sampler and procedure.......................................................................................................11
Specific applications ...................................................................................................................................12
Compliance with parts 1 and 2 of this standard .......................................................................................12

7
7.1
7.2
7.3
7.4
7.4.1
7.4.2
7.4.3
7.4.4
7.4.5

Operating principles ....................................................................................................................................12
Principles of diffusive sampling.................................................................................................................12

Dimensions of diffusive uptake rate ..........................................................................................................13
Bias due to the selection of a non-ideal sorbent......................................................................................13
Environmental factors affecting sampler performance ...........................................................................14
Temperature and pressure..........................................................................................................................14
Humidity........................................................................................................................................................14
Transients .....................................................................................................................................................15
Influence of air velocity ...............................................................................................................................15
Transportation..............................................................................................................................................16

8
8.1
8.2
8.3
8.4
8.5

Protection from adverse environmental conditions.................................................................................16
General..........................................................................................................................................................16
Air velocity....................................................................................................................................................16
Precipitation .................................................................................................................................................16
Provision of a shelter ..................................................................................................................................17
Security .........................................................................................................................................................17

9

Arrangement of sampling points................................................................................................................17

10

Requirements for training ...........................................................................................................................17

11

Quality assurance ........................................................................................................................................18

Annex A (informative) Specific applications ..........................................................................................................19
A.1
General..........................................................................................................................................................19
A.2
Nitrogen oxides ............................................................................................................................................19
A.2.1 Tube-type samplers .....................................................................................................................................19
A.2.2 US Environmental Protection Agency (EPA)/Monsanto badge ..............................................................19
2


EN 13528-3:2003 (E)

A.3
A.4
A.5
A.6
A.6.1
A.6.2
A.6.3
A.7
A.8
A.9
A.10

Nitrogen monoxide ......................................................................................................................................20

Sulphur dioxide............................................................................................................................................20
Ammonia.......................................................................................................................................................21
Organic gases (Volatile Organic Compounds or VOCs)..........................................................................21
Tube-type samplers .....................................................................................................................................21
Badge-type samplers...................................................................................................................................22
Radial samplers ...........................................................................................................................................22
Formaldehyde ..............................................................................................................................................22
Ozone ............................................................................................................................................................23
Shelters.........................................................................................................................................................23
Design of Standard Atmosphere Apparatus.............................................................................................28

Annex B (informative) Characteristics of some diffusive samplers ....................................................................29
Bibliography ..............................................................................................................................................................32

3


EN 13528-3:2003 (E)

Foreword
This document (EN 13528-3:2003) has been prepared by Technical Committee CEN/TC 264 “Air quality”, 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 June 2004, and conflicting national standards shall be withdrawn at the latest by
June 2004.
This European Standard is a multi-part standard having the following parts:
EN 13528-1, Ambient air quality - Diffusive samplers for the determination of concentrations of gases and vapours Requirements and test methods - Part 1: General requirements.
EN 13528-2, Ambient air quality - Diffusive samplers for the determination of concentrations of gases and vapours Requirements and test methods - Part 2: Specific requirements and test methods.
EN 13528-3, Ambient air quality - Diffusive samplers for the determination of concentrations of gases and vapours Requirements and test methods - Part 3: Guide to selection, use and maintenance.
Annexes A and B of this part of the European Standard are informative.

This document includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,
Slovakia, Spain, Sweden, Switzerland and the United Kingdom.

4


EN 13528-3:2003 (E)

Introduction
This European Standard specifies requirements and test methods for the determination of performance
characteristics of diffusive samplers used for the determination of concentrations of gases and vapours in ambient
atmospheres.
th

With regard to air quality, the objectives fixed in the 5 Action Program of the European Union are for the effective
protection of all people against recognised risks from air pollution and the establishment of permitted concentration
levels of air pollutants, which should take into account the protection of the environment. These objectives include
monitoring and control of concentrations with regard to standards.
Successive programs of action of the European Union on the protection of the environment have stressed the need
to find a balance between the use of different tools: product standards, emission limits and environmental
objectives/standards.
The implementation of existing Directives has highlighted the existence of various problems, which are being
addressed in the Council Directive on Ambient Air Quality Assessment and Management [1]. These include:


different monitoring strategies in comparable situations between and within Member States;



harmonisation of measuring methods;



quality of the measurements which depend on the calibration and quality assurance procedures.

Diffusive samplers used to measure air quality should fulfil some general requirements which are given in
EN 13528-1. These requirements include unambiguity, selectivity and Data Quality Objectives, including
uncertainty.
Such general requirements can also be appropriate for other measuring procedures used in the assessment of
ambient air quality.
In addition, diffusive samplers used to measure ambient air quality should also fulfil some specific requirements in
addition to those specified in EN 13528-1. These specific requirements are given in EN 13528-2. This part of
EN 13528 gives guidance on the selection, use and maintenance of diffusive samplers used to measure ambient
air quality.
It is the user's primary responsibility to choose appropriate procedures or devices that meet the requirements of
this European Standard. One way of doing this is to obtain information or confirmation from the manufacturer. Type
testing, or more generally, the assessment of performance criteria of procedures or devices, can be undertaken by
the manufacturer, user, test house or research and development laboratory, as is most appropriate.
Although this standard specifically addresses ambient air, diffusive sampling is also relevant to the assessment of
air quality in indoor air. Both pumped and diffusive sampling procedures are considered appropriate for such
measurements, depending on circumstances (particularly any requirement for time resolution) [2]. prEN 14412
gives guidance on the selection, use and maintenance of diffusive samplers used to measure indoor air quality.
This part of EN 13528 is similar in content to EN 838 and EN 13528-1 is similar in content to EN 482. The series of
standards on the use of diffusive samplers for ambient air has been created in addition to those for workplace air
because the underlying European Directives are different and the consequent definitions and practical applications
of the estimation of the uncertainty of measurements are different.

5


EN 13528-3:2003 (E)

1

Scope

This part of the European Standard gives guidance on the selection, use and maintenance of diffusive samplers
used to measure ambient air quality. It includes guidance on measurement objectives and strategies, both in
support of European Community Policy and more generally, relevant to the use of such samplers. It also includes
information on the operating principles of diffusive samplers and the factors that affect performance in the practical
implementation of such policies. Advice is also given on ways to minimise any such adverse effects, e.g. by
suggesting shelters that may protect against the effects of wind speed on the samplers, and on training and quality
assurance considerations.
Annexes give further information on practical applications for particular environmental pollutants, including those
specified by existing and anticipated European Daughter Directives.

2

Normative references

This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
ENV 13005, Guide to the expression of uncertainty in measurement.
EN 13528-1:2002, Ambient air quality - Diffusive samplers for the determination of concentrations of gases and

vapours - Requirements and test methods - Part 1: General requirements.
EN 13528-2:2002, Ambient air quality - Diffusive samplers for the determination of concentrations of gases and
vapours - Requirements and test methods - Part 2: Specific requirements and test methods.
ISO 5725 (all Parts), Accuracy (trueness and precision) of measurement methods and results.

3

Terms and definitions

NOTE
[1].

Attention is drawn to the fact that the terms Assessment, Limit Value and Pollutant are defined in Directive 96/62/EC

For the purposes of this European Standard the following terms and definitions apply.
3.1
ambient air
outdoor air in the troposphere, excluding indoor air and workplaces
3.2
averaging time
period of time for which the measuring procedure yields a single value [EN 482:1994]
3.3
diffusive sampler
device which is capable of taking samples of gases or vapours from the atmosphere at a rate controlled by a
physical process such as gaseous diffusion through a static air layer or a porous material and/or permeation
through a membrane, but which does not involve the active movement of air through the device
NOTE 1

Active normally refers to the pumped movement of air.

NOTE 2

This definition differs from that in EN 838 by the addition of the words “or a porous material”.

6


EN 13528-3:2003 (E)

3.4
diffusive uptake rate
rate at which the diffusive sampler collects a particular gas or vapour from the atmosphere, expressed in picograms
-1
-1
3
-1
per parts per billion1 per minute (pg ppb min ) or cubic centimetres per minute (cm min )
NOTE 1

-1

-1

-1

-1

pg ppb min are equivalent to ng ppm min .

NOTE 2

This definition differs from that in EN 838 by the substitution of “picograms per parts per billion” for “nanograms per
parts per million”. The expression is numerically the same, but ambient concentrations are usually in the ppb range.

3.5
measuring procedure
procedure for sampling and analysing one or more pollutants in ambient air and including storage and
transportation of the sample
3.6
selectivity
degree of independence from interferents
3.7
uncertainty (of measurement)
parameter, associated with the results of a measurement, that characterises the dispersion of values that could
reasonably be attributed to the measurand
NOTE 1
The parameter can be, for example, a standard deviation (or given multiple of it), or the half width of an interval
having a stated level of confidence.
NOTE 2
Uncertainty of measurement comprises, in general, many components. Some of these components can be
evaluated from the statistical distribution of the results of a series of measurements and can be characterised by experimental
standard deviations. The other components, which can also be characterised by standard deviations, are evaluated from
assumed probability distributions based on experience or other information.
NOTE 3
It is understood that the result of a measurement is the best estimate of the value of a measurand, and that all
components of uncertainty, including those arising from systematic effects, such as components associated with corrections and
reference standards, contribute to this dispersion [ENV 13005].

3.8
validation
process of evaluating the performance of a measuring procedure and checking that the performance meets certain

pre-set criteria

4

Symbols and abbreviations

A

cross-sectional area of the diffusion path, or equivalent sorption surface, in square centimetres;

C

observed concentration, in micrograms per cubic meter;

D

diffusion coefficient of analyte, in square centimetres per minute;

D1 diffusion coefficient of analyte 1, in square centimetres per minute;
D2 diffusion coefficient of analyte 2, in square centimetres per minute;
d

desorption efficiency;

k

correction factor for non-ideal behaviour (see 7.1);

1 ppb is volume fraction, (φ)=10-9; ppm is volume fraction, (φ)=10-6.

7


EN 13528-3:2003 (E)

l

length of static air layer in sampler (or equivalent for permeation types), in centimetres;

M

molar mass of analyte, in grams per mol;

mb mass of the analyte which is desorbed from the blank sampler, in picograms;
md mass of the analyte which is desorbed from exposed samplers, in picograms;
ms mass of the analyte which is sorbed by diffusion, in picograms;
P

pressure of the sampled atmosphere during sampling, in kilopascals;

t

exposure time, in minutes;

T

temperature of the atmosphere sampled, in Kelvin;

U

diffusive uptake rate, in cubic centimetres per minute;

U1 diffusive uptake of analyte 1, in cubic centimetres per minute;
U2 diffusive uptake of analyte 2, in cubic centimetres per minute;
-1

-1

U'

diffusive uptake rate, in picograms per parts per billion per minute (pg ppb min );

V

volumetric flow of air, in cubic meters per minute;

δ

bias;

φ

delivered concentration in parts per billion (volume fraction = 10 );

ρ

delivered concentration, in micrograms per cubic meter;

ρ1

concentration of the given analyte at the beginning of the diffusion layer (l = 0), in micrograms per cubic
meter;

ρ2

concentration of the given analyte at the end of the diffusion layer, in micrograms per cubic meter;

τ

time constant of the diffusive sampler, in seconds.

5

-9

Measurement objectives and strategy

5.1 Measurements in support of Community Policy
NOTE

5.1.1

It is the responsibility of the user of the standard to check the latest developments of EU legislation.

Air Quality Directives

Different regimes of air quality assessment are possible for the implementation of the Council Directive on Ambient
Air Quality Assessment and Management [1], and successive Daughter Directives, in which the measurement
requirements are relaxed as the risk of exceeding the limit values decreases.
Measurements at fixed measuring stations, indicative measurement methods, emission inventories and air quality

modelling, or a combination of techniques, may be used, depending on whether the pollutant concentration levels
over a representative period are above or below one or more set percentages of the relevant limit value. Generally,
the closer the concentration is to the limit value, the more demanding are the data quality objectives (see below).
The percentages, for both the upper and lower assessment thresholds, as defined in EC-Directive 96/62/EC [1], are

8


EN 13528-3:2003 (E)

given in the relevant daughter Directives, e.g. EC-Directive 99/30/EC [3], Annex V for sulphur dioxide, nitrogen
dioxide and oxides of nitrogen; and Directive 2000/69/EC [4], Annex III for benzene and carbon monoxide.
Data quality objectives are set for each measurement type to guide quality assurance programmes. These data
quality objectives include the required accuracy (uncertainty), the minimum time coverage and the percentage data
capture of the assessment methods. Numerical values of the objectives are given in the relevant daughter
Directives, e.g. EC-Directive 99/30/EC [3], Annex VIII for sulphur dioxide, nitrogen dioxide and oxides of nitrogen;
Directive 2000/69/EC [4], Annex VI for benzene and carbon monoxide; and Directive 2002/3/EC [5], Annex VII for
ozone.
The uncertainty (at a 95 % confidence interval) of the assessment methods will be evaluated in accordance with
the Guide to the Expression of Uncertainty in Measurement (ENV 13005) and/or ISO 5725 or equivalent.
The diffusive sampling technique may be implemented under the Air Quality Directives for:


classification of zones (Art. 8 and 9);



preliminary assessment of ambient air quality (Art. 5);



network design/optimisation (Art. 4.3);



air quality monitoring in areas at no risk of exceeding limit values (Art. 6.3);



determination of areas of homogeneous air quality;



assessment of pollution in the vicinity of point sources (traffic, industry);



assessment of pollution in ecosystems.

Further guidance on the potential of diffusive sampling in connection with Preliminary Assessment under EC Air
Quality Directives is given in the report [6].
Detailed requirements for the assessment of concentrations of atmospheric pollutants, with special reference to the
potential of diffusive sampling, have been developed by VDI [7].
5.1.2

Source-related assessment

Diffusive sampling is already established within industry for workplace monitoring [EN 482]; however the
techniques have yet to be widely accepted for monitoring of ambient air within industrial areas.
In addition to the tasks mentioned in 5.1.1 diffusive sampling can be used for:



environmental Impact Assessments studies needed to obtain exploitation permits;



measurement campaigns for the identification of sources;



surveys to monitor the environmental impact of industrial processes within plants;



ground level air quality impact of factory sites by deployment at boundary fences;



air quality monitoring campaigns with local authorities within communities and rural areas neighbouring major
industrial complexes to demonstrate compliance with and maintenance of air quality objectives in EC
Directives and national air quality standards.

Diffusive samplers are already available for various substances and/or can be designed to measure almost all
gases emitted by industrial and other processes, including oxides of nitrogen and sulphur, ammonia and amines,
chlorinated hydrocarbons, oxygenated species including solvents and aldehydes, halogen and acid gases,
hydrogen sulphide and many others (annex A).
9


EN 13528-3:2003 (E)

5.1.3

Forest Protection directives

Diffusive sampling is also relevant to the Council Regulation (EEC) No. 3528/86 (amended by Regulation (EEC)
No. 2157/92) on the protection of the Community's forests against atmospheric pollution, and establishing a
network of permanent observation sites for the intensive and continuous surveillance of forest ecosystems [8].
5.1.4

Protection of ecosystems

Diffusive sampling is also relevant to Proposal COM(99)125 final [5], in that Annex II (section III) establishes
reference exposure levels relating to damage by ozone to materials and forests, and visible damage to crops.
5.1.5

Public awareness

The right of the public to be informed about its exposure to air pollutants and the state of its environment has
become one of the priorities of the air quality policies. The cost effectiveness and simple operation of diffusive
samplers make it an ideal tool for the organisation of campaigns for the information of the public. In particular the
technique can be usefully implemented for the organisation of awareness raising campaigns and for didactic
purposes.

5.2 Measurement in support of other policies
5.2.1

Measurement in support of national, regional or local policies

A limited number of local authorities in Member States have already taken pro-active measures to assess ambient

air quality within their urban and rural environments. However, measurements methods used to date tend to be
based on fixed point monitoring stations which are only partly representative of the spatial variations in ambient air
quality. Determining the spatial location of such sites can be difficult. In addition, such techniques are expensive.
Diffusive sampling provides an excellent tool for screening campaigns to estimate air quality at many locations
simultaneously. An example is given in [9, 10; other examples available in literature]. Such campaigns complement
data obtained from fixed stations such that a local authority can confidently assess local ambient air conditions and
make decisions about network design for future campaigns.
5.2.2

Protection of special ecosystems

Special sensitive ecosystems such as natural reserves and mountain areas are not specifically covered by existing
Community limit values or national air quality regulations but may be protected by particular and more stringent
regulations. The simplicity of operation of the diffusive sampling technique and the lack of a requirement for electric
power renders this technique well adapted to this scope, in particular for the assessment of integrated pollution
levels over longer periods of time.
The technique can similarly be used for the protection of our cultural heritage (historical, monuments, paintings,
etc.).
5.2.3

Particular research aspects

Diffusive samplers can be used in response to particular research needs, such as for:


analysis of trends in air quality;



study of the source/receptor relationship;



validation of atmospheric dispersion models;



evaluation of emission reduction measures;



collecting exposure data for epidemiology or risk assessment.

10


EN 13528-3:2003 (E)

5.3 Measurement strategy
The measuring strategy will depend on the objectives of the monitoring, and the pollutants to be assessed. It is
necessary to specify where, how, and how often measurements shall be taken. The measuring effort will be
dependent on:


variation of pollutant concentrations in space and time;



availability of supplementary information;



accuracy of the estimate that is required.

A practical example of the development of a measurement strategy in connection with Preliminary Assessment
under EC Air Quality Directives is given in the report [6].

6

Selection of the device

6.1 Sources of information
Important information on the performance characteristics of a diffusive sampler can be obtained from various
sources. These include:


manufacturer's instructions for use (EN 13528-2:2002, 5.12);



published commercial technical information;



technical and research publications;



national and international standards [11-15];



user groups, e.g. HSE/CAR/WG 5 (Health and Safety Executive / Committee on analytical Requirements/
2
Working Group 5), which issues The Diffusive Monitor, a newsletter produced since 1988 .

6.2 Selection of a sampler and procedure
The selection of a diffusive sampler will depend on many factors. These include:
a) measurement task (clause 5); i.e.


mandatory measurements;



indicative measurements;



objective assessment;



measurements other than required by the Framework Directive[1];

b) specified measuring range required, with special reference to the sampling time, the detection limit, the uptake
rate and the possibility of reaching the equilibrium saturation capacity of the sorbent medium of the sampler
(see annex B);
c) time resolution required;

2 obtainable from the Health and Safety Laboratory, Broad Lane, Sheffield S3 7HQ, UK

11


EN 13528-3:2003 (E)

d) selectivity to the target gas or vapour and sensitivity to interfering gases and vapours (EN 13528-1:2002, 5.2);
e) relevant Data Quality Objectives (EN 13528-1 :2002, 5.3);
f)

susceptibility of the sampler to environmental factors (7.4), particularly air velocity;

g) adequate protection from adverse environmental conditions (see clause 8);
h) fitness for purpose, e.g. size, weight, durability (see 6.4);
i)

training requirements for the reliable operation, maintenance and calibration (see clause 10);

j)

total cost of purchase and operation, including calibration and maintenance;

k) compliance with the performance requirements of Parts 1 and 2 and appropriate national regulations (see 6.4);
l)

conformity to the user's quality system (see clause 11).

6.3 Specific applications
Specific applications of diffusive samplers for environmental pollutants are given in annex A.

6.4 Compliance with parts 1 and 2 of this standard
Marking EN 13528 on or in relation to a product represents a manufacturer's declaration of conformity, i.e. a claim
by or on behalf of the manufacturer that the product meets the requirements of this European Standard. The
accuracy of the claim is therefore the responsibility of the person making the claim.

7

Operating principles

7.1 Principles of diffusive sampling
The mass of the analyte which can diffuse to a suitable sorbent within a certain time is determined by the equation
which is derived from Fick's first law of diffusion:

ms =

A × D × (ρ 1 − ρ 2 ) × t
l

(1a)

This equation differs from equation (A.2) in Part 2, because it refers to the more general situation where ρ2 may be
non-zero. Ideally ρ1 is equal to the concentration of the given analyte in the air outside the diffusive sampler (ρ),
and ρ2 equals zero ("zero sink"-condition). In that case the magnitude of the diffusive uptake rate, A × D/l, is
dependent only on the diffusion coefficient of the given analyte and on the geometry of the diffusive sampler used.

12


EN 13528-3:2003 (E)

Figure 1 — Diagram of diffusion process
The inlet of a sampler with cross-section A at position 1 defines the beginning of the diffusion path of an analyte
with a concentration of ρ1. A sorbent B at position 2, which will reduce the concentration of the analyte, ρ2, to zero
(ideally) due to sorption or chemical reaction, serves as the driving force for the diffusion along l.
In practice, there are a number of factors that can give rise to non-ideal behaviour, so that:

ms =
NOTE

A×D× ρ ×t ×k
l

(1b)

k can be a function of concentration and time of exposure (see 7.3).

A general overview of the principles of diffusive sampling is given in [16].

7.2 Dimensions of diffusive uptake rate
For a given concentration ρ in micrograms per cubic metre of gas or vapour, the diffusive uptake rate is given by:

U =

ms
ρ ×t

(2a)

NOTE 1

Although the uptake rate, U, has dimensions of volume per unit time; this does not indicate a real volumetric flow of
(analyte in) air.
NOTE 2
Diffusive uptake rates are very often quoted in units of pg⋅ppb ⋅min . These are practical units, since most
environmental analysts use ppb for concentrations of gases and vapours. The dependency of uptake rates on temperature and
pressure is explained later (7.4.1). Thus for a given concentration (ppb) of gas or vapour, the sampling rate is given by:
-1

U' =
NOTE 3

U' =

ms
φ ×t

-1

(2b)

U' and U are related by:

U × M × 293 × P
24,0 × T × 101

(3)

7.3 Bias due to the selection of a non-ideal sorbent
The performance of a diffusive sampler depends critically on the selection and use of a suitable sorbent. In the
case of a collection medium, which has high sorption efficiency, the residual vapour pressure of the sampled

13


EN 13528-3:2003 (E)

compound at the sorbent surface (ρ2) will be very small in comparison to the ambient concentration. The observed
uptake rate will then be close to its ideal steady-state value, which can usually be calculated from the geometry of
the sampler and the diffusion coefficient of the analyte in air.
In the case where a weak sorbent is used, then ρ2 in equation 1a is non-zero and ms/t will decrease with the time of
sampling. In the alternative expression, equation 1b, k has a value significantly less than unity. Hence U in
equations 2 will also decrease with the time of sampling. The concentration of the sampled pollutant can also have
a (lesser) effect on ms/t and hence on U. The magnitude of these effects is dependent on the adsorption isotherm
of the analyte and sorbent concerned, and may be calculated with the aid of computer models [17,18].
Another manifestation of the same effect is back diffusion, sometimes called reverse diffusion. This can happen
where, some time after sampling has started, the vapour pressure of the analyte at the sorbent surface, ρ2, is
greater than the external concentration, ρ1, for example if a sampler is first exposed to a high concentration and
then to a much lower or even zero concentration. This type of exposure profile can occur in certain applications,
and the magnitude of any error introduced will depend on whether the period of high concentration occurs at the
beginning, middle, or end of the sampling period. The phenomenon has been discussed in detail by Bartley and
others [19-21] and a simple test proposed [22] to give an estimate of the maximum bias to be expected between a
pulsed exposure and an exposure to a constant concentration, which latter normally provides the basis for the
sampler calibration. This test is 30 min exposure to a high concentration, followed by 7,5 h of clean air, and has
been adopted in EN 838. For ambient air applications (EN 13528-2:2002, 7.3.1), however, it is considered that an
exposure profile of alternate equal periods of high and low exposure for a 24-h cycle is more typical of the intended
application, where diurnal variations in concentration are common. The extent of back-diffusion can also be
modelled theoretically [18,23].
It is therefore desirable to choose a sorbent with high sorption capacity and low vapour pressure of the sorbed
material or of the reaction product formed by a reactive sorbent.

7.4 Environmental factors affecting sampler performance

7.4.1

Temperature and pressure

For an ideal diffusive sampler, the dependence of U on absolute temperature and pressure is governed by that of
the diffusion coefficient of the analyte. The latter dependence is given by:

(

D = f T n +1 , P −1

)

(4)

with 0,5 < n < 1,0.
Hence, the dependence of U, expressed in units of cm ⋅min or equivalent is:
3

(

U = f T n +1 , P −1

-1

)

(5)

When U' is expressed in units of pg.ppb ⋅min or equivalent by application of equation 3, then the dependence is

given by:
-1

-1

( )

U '= f T n

(6)
-1

-1

In the latter case, the dependence will be of the order of 0,2 % K to 0,4 % K . In the case of a non-ideal sampler,
the temperature dependence of U' may be compensated by the temperature dependence of the sorption coefficient
of the analyte [24]. In any case, accurate knowledge of the average temperature and pressure during the sampling
period is important for a correct application of equations 2a and 2b.
7.4.2

Humidity

High humidity can affect the sorption capacity of hydrophilic sorbents, such as charcoal and Molecular Sieve. This
will normally reduce the sampling time (at a given concentration) before saturation of the sorbent occurs, when
sampling becomes non-linear because of a significant ρ2 term in equation 1. High humidity can also alter the

14


EN 13528-3:2003 (E)

sorption behaviour of the exposed inner wall of tube-type samplers or draught screen, particularly if condensation
occurs.
7.4.3

Transients

Simple derivations of Fick's Law assume steady state conditions, but in the practical use of diffusive samplers, the
ambient level of pollutants is likely to vary widely. The question then arises whether a sampler will give a truly
integrated response (ignoring sorbent effects, see 7.4.1) or will "miss" short-lived transients before they have had a
chance to be trapped by the sorbent. The problem has been discussed theoretically [19, 25-27] and practically [25,
28-29] and shown not to be a problem, provided the total sampling time is well in excess of (say 10 times) the time
constant τ, of the diffusive sampler. τ is the residence time of the pollutant molecule in the diffusive pathway. Its
value is given by:

τ =

l2
D

(7)

For most commercial samplers, τ is between about 1 s and 10 s.
7.4.4
7.4.4.1

Influence of air velocity
Effect of low and high wind speeds

Wind speed and direction (i.e. from the point of view of the sampler, the ambient air face velocity and the sampler

orientation) can affect the performance of a diffusive sampler because they may influence the effective diffusion
path length [30-33]. The diffusive mass uptake of a sampler (equation 1) is a function of the length, l, and the crosssectional area, A, of the diffusion gap within the sampler. The nominal diffusion path length is defined by the
geometry of the sampler and is the distance between the sorbent surface and the external face of the sampler. The
cross-sectional area is also defined by the geometry of the sampler and if the cross-section of the diffusion gap is
not constant along its length, is defined by the narrowest portion. The effective length, l, is not necessarily the same
as the nominal length, and may be greater or less, depending on circumstances.
Under conditions of low external wind speeds, the effective diffusion path length may be increased [32,33]. This is
because a 'boundary layer' [30,31] exists between the stagnant air within the sampler and the moving air outside
and contributes to the effective diffusion path length, l. In reality, there is an area outside the sampler where there is
a transition between static air and moving air, but this is equivalent to an extra length (∆l) of static air, which must
be included in the value of l. The value of ∆l depends on the external geometry of the sampler. It also decreases
with increasing air velocity. Its significance depends on the value of the nominal path length of the diffusive
sampler. Thus a sampler with a small cross-section and long internal air gap will be relatively unaffected by air
velocity, whilst a short, fat sampler will be significantly affected. This is borne out in practice, as has been
demonstrated with samplers of varying length [32, 33]. Low sampling rates are observed at low air velocities, but
increase to a plateau value as the boundary layer effect becomes insignificant.
Under conditions of high external wind speeds, the effective diffusion path length may be decreased [34, 35-40].
This is because external high airflows disturb the static air layer within the sampler, which reduces the effective air
gap by a (different) factor ∆l. The value of ∆l is small, provided the length to diameter ratio of the sampler air gap is
greater than 2,5 to 3 [34], or it can be avoided, or greatly reduced, by incorporating a draught shield, e.g. a
stainless steel screen or plastic membrane. An alternative to using a draught shield is to place the sampler in a
protective housing, but in this case, the housing shall completely surround the sampler (see also 8.4).
The overall effect is therefore an s-shaped curve (EN 13528-2:2002, 7.4, Figure 1).
7.4.4.2

Consequence for different sampler geometries

Tube-type samplers are typically unaffected by low air velocities [25, 41,42] but those without a draught shield may
be affected by high speeds.

15


EN 13528-3:2003 (E)

Badge-type samplers generally have a large surface area and small air gap, so that they may be more affected by
-1
-1
air velocity than tube designs and typically require a minimum face velocity of between 0,5 m⋅s and 0,2 m⋅s [4346]. Some badges with an inadequate draught shield are also affected at high air velocities [42, 44, 47].
-1

Radial diffusive samplers [48, 49] require a minimum face velocity of about 0,25 m⋅s .
7.4.5

Transportation

Most samplers will require transportation between the sampling site and an analytical laboratory, so that it is
important that sample integrity is maintained during this process. The following precautions are recommended:
a)

Ensure that any seals are sufficiently tight to avoid ingress of contamination or loss of sample during transit:
metal - plastic seals may become loose if a large temperature change takes place;

b)

Place the samplers in inert closed containers to minimise the ingress of external contamination;

c)

If air-freighting samples, ensure that they are not subjected to negative pressure, e.g. in the baggage hold;

d)

Avoid exposure to high temperatures during transit, e.g. in the boot of a car;

e)

If possible, keep the samplers at low temperature, low humidity and away from contamination sources e.g.
fuels, but avoiding condensation on the sample.

Ensure that adequate sample blanks are transported with the samples so that any of the above problems can be
identified.

8

Protection from adverse environmental conditions

8.1 General
In practical use in the ambient environment, attention has to be paid to three main considerations; air velocity,
protection from precipitation, and security.

8.2 Air velocity
The potential effect of air velocity is described in 7.4.4. Monthly averaged ambient wind velocities in Europe are
-1
-1
-1
mostly in the range 1 m⋅s to 10 m⋅s [50] but can fall below 0,5 m⋅s temporarily in the case of stable
meteorological conditions (inversions) and/or locally in valleys of mountainous areas [50, 51]. Moreover, at least for
local source emissions, pollutant concentrations are inversely proportional to wind speed [52] so any sampling error
at low wind speeds would be magnified in the time-weighted average.

For samplers which are affected at low wind speeds, and if exposure to such conditions is likely to be significant,
then some additional ventilation is necessary. This could be achieved by using a small fan for forced ventilation:
this might defeat the object of using a 'passive' sampler, but could be practicable with solar power in more southern
climates. Alternatively, samplers might be suspended on a fine thread to increase the effect of small air movements
[53].
Similarly, for samplers which are affected at high wind speeds, some attenuation of the air velocity is necessary.
Even where moderate wind speeds are expected, problems can arise if samplers are placed too close to buildings
or other obstacles. Consideration shall be given to the size and location of the obstacle(s) in the sitting of the
sampler (see clause 9).

8.3 Precipitation
Protection from precipitation is important for all types of sampler. Rain or melted snow can block the sampling
surfaces [54], particularly of tube samplers oriented vertically downwards (which is the usual position to avoid
ingress of particulates).
16


EN 13528-3:2003 (E)

8.4 Provision of a shelter
In order to minimise the potential problems identified in 8.2 and 8.3, a shelter should be used. The shelter has to be
optimised for the sampler type, taking the following into account:


the shelter shall protect the sampler from high air velocities and precipitation, but there shall be sufficient air
exchange to determine values, which are representative for air, and to satisfy any minimum velocity
requirement;



the design of the shelter and the means of locating the sampler shall not significantly affect the diffusive uptake
rate of the sampler;



the construction, surface and colour of the shelter shall be such to minimise temperature rise due to direct
solar radiation.

An alternative to providing a shelter is to modify the diffusive sampler. For example, the diffusion end cap of a tubetype sampler can be modified with the addition of an aluminium brim to prevent rainwater blocking the diffusion
surface [55]. However, such an arrangement may modify the performance characteristics of the sampler with
respect to the minimum air velocity requirement.

8.5 Security
Security is also a major consideration, as samplers exposed for long periods in public or semi-public places are
subject to theft and vandalism. Samplers should be sited, so far as possible, to be out of reach, inconspicuous
and/or designed to look like something else, e.g. the nest box idea.

9

Arrangement of sampling points

The number, location and height of sampling points should be selected in such a way, as a function of the
measurement task, that answers to the specific questions posed can reasonably be expected. Once chosen, the
sampling points should not be changed during the measurement programme.
Unless otherwise specified, suitable sampling points should be at least 1 m away from buildings or other major
obstructions to avoid local perturbation effects. The measuring height should be between 1,5 m and 4,0 m: at least
2,5 m will discourage theft and vandalism. The immediate vicinity of trees, bushes, etc. should be avoided to
minimize the influence of the local environment or to minimize effects from troublesome insects.

10 Requirements for training

For most apparatus, specialist training is required for both the operator and those responsible for the maintenance
and calibration. Diffusive samplers, however, do not require a specialist operator for their deployment, provided that
clear and unambiguous instructions for use are available (see EN 13528-2:2002, 5.10) and due note is taken of the
above guidance. A minimum of practical training is indispensable for operators to avoid common errors like
smoking during work, working directly near a car with its engine running, touching inner surfaces of the sampler
with the fingers, or using felt-tip pens for marking.
Maintenance, however, is as important for diffusive samplers as for other devices, and particular attention should
be made to the following:
a) For re-usable devices, ensure that the collection element is intact, clean, or replaced as necessary;
b) Ensure that all component parts are free from contamination;
c) Ensure that the devices are used in accordance with EN 13528-1 and EN 13528-2;
d) Ensure that devices are used within the manufacturer's recommended shelf-life.
17


EN 13528-3:2003 (E)

11 Quality assurance
It is good practice to set up a quality assurance scheme for the maintenance and calibration of the samplers. This
includes:
a)

the establishment of a Standard Operating Procedure (SOP);

b)

for re-usable devices, a log of usage;

c)

keeping a record of the traceability of the calibration;

d)

retaining the raw data as required by the quality or other system;

e)

using a unique sampler numbering system. Re-usable samplers shall be in addition labelled with a durable
identification;

f)

depending on the measurement task, taking an appropriate number of field blank and replicate samples (e.g.
10 %);

g)

for internal QA, to check diffusive sampling rates routinely; at least once during large surveys. This may be
done by exposing samplers in laboratory standard atmospheres or by laboratory or field comparisons with an
independent (e.g. pumped) method (see A.10);

h) for external QA, to check diffusive sampling rates routinely; at least once during large surveys. This may be
done by laboratory or field intercomparisons, which should be conducted by experienced institutes (see A.10);
i)

18

sampling protocol including relevant information on sampling such as measurement location, measurement
period, sampler identification, operator.