EN 14662-3:2005

SLOVENSKI STANDARD
01-september-2005
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Ambient Air Quality - Standard method for the measurement of benzene concentrations -
Part 3: Automated pumped sampling with in situ gas chromatography
Luftbeschaffenheit - Standardverfahren zur Bestimmung von Benzolkonzentrationen -
Teil 3: Automatische Probenahme mit einer Pumpe mit gaschromatographischer In-situ-
Bestimmung
Qualité de l'air ambiant - Méthode normalisée pour le mesurage de la concentration en
benzene - Partie 3 : Prélevement par pompage automatique avec analyse
chromatographique en phase gazeuse sur site
Ta slovenski standard je istoveten z: EN 14662-3:2005
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14662-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2005
ICS 13.040.20
English version
Ambient Air Quality - Standard method for the measurement of
benzene concentrations - Part 3: Automated pumped sampling
with in situ gas chromatography
Qualité de l'air ambiant - Méthode pour le mesurage des Luftbeschaffenheit - Standardverfahren zur Bestimmung
concentrations en benzène - Partie 3 - Echantillonnage par von Benzolkonzentrationen - Teil 3: Automatische
pompage automatique suivi d'une chromatographie en Probenahme mit einer Pumpe mit gaschromatographischer
phase gazeuse in situ In-situ-Bestimmung
This European Standard was approved by CEN on 21 March 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14662-3:2005: E
worldwide for CEN national Members.

Contents
Foreword .3
1 Scope.4
2 Normative references .4
3 Terms and definitions.4
4 Symbols and abbreviated terms.8
5 Principles.9
6 Reagents and materials.10
7 Apparatus .11
8 Type approval.12
9 Field Operation and Ongoing Quality Control .25
10 Reports and documentation .33
Annex A (normative) Test of lack of fit.35
Annex B (informative) Calculation of uncertainty in field operation at the limit value for
individual measurements .37
Annex C (informative) An example of the results of an inter-calibration exercise.39
Annex D (informative)  Components and applications of type approved benzene monitors .42
Bibliography.44

Foreword
This European Standard (EN 14662-3:2005) 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 November 2005, and conflicting national standards
shall be withdrawn at the latest by November 2005.
This document has been prepared under a mandate given to CEN by the European Commission and
the European Free Trade Association, and supports essential requirements of EU Directive
2000/69/EC and EU Directive 96/62 EC.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia,
Spain, Sweden, Switzerland and United Kingdom.
1 Scope
This part of EN 14662 is in accordance with the generic methodology selected as the basis of the
European Union Reference Method for the determination of benzene in ambient air [1] for the purpose
of comparison of measurement results with limit values with a one-year reference period.
The standard describes guidelines for measurements with, and type approval of, automated gas
chromatographs. The use of automated instruments gives this part a different structure compared to
the other parts including the procedure for selecting an appropriate automated gas chromatograph by
means of type approval tests.
Requirements for use in the field are also described.
The standard is applicable to measurements of airborne benzene vapour in the concentration range
3 3
from 0 µg/m to 50 µg/m (Standardised to 101,3 kPa and 293 K). This concentration range represents
the certification range for benzene in the type approval test.
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.
ENV 13005, Guide to the expression of uncertainty in measurement
EN ISO 14956, Air quality - Evaluation of the suitability of a measurement procedure by comparison
with a required measurement uncertainty (ISO 14956:2002)
EN ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:1999)
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results - Part 2:
Basic method for the determination of repeatability and reproducibility of a standard measurement
method
ISO 5725-3:1995, Accuracy (trueness and precision) of measurement methods and results - Part 3:
Intermediate measures of the precision of a standard measurement method
ISO 6142: 2001 Gas analysis – Preparation of calibration gas mixtures - Gravimetric method
ISO 6143 Gas analysis – Determination of the composition of calibration gas mixtures – Comparison
methods
ISO 6144 Gas analysis - Preparation of calibration gas mixtures - Static volumetric method
ISO 6145 (all parts) Gas analysis - Preparation of calibration gas mixtures - Dynamic volumetric
methods
3 Terms and definitions
For the purposes of this European Standard the following terms and definitions apply.
3.1
Ambient air
outdoor air in the troposphere
3.2
Ambient temperature
temperature at the sample inlet outside the monitoring station
3.3
Availability of the analyser
fraction of the total time period for which valid measuring data of the ambient air concentration is
available
3.4
Calibration
comparison of the analyser response to a known gas concentration with a known uncertainty
3.5
Carry-over (memory effect)
influence of the previous measurement due to the retention of benzene within the instrument
3.6
Certification range
concentration range for which the analyser is type approved
3.7
Combined standard uncertainty
calculation result of combining the standard uncertainties calculated from all performance
characteristics specified in this standard according to the prescribed procedure given in this standard
3.8
Designated body
body (which can be a laboratory) which has been designated for a specific task (type approval tests
and/or QA/QC activities in the field) by a competent authority in the Member States
NOTE It is recommended that the designated body is accredited for the specific task according to EN
ISO/IEC 17025
3.9
Detection limit
lowest concentration level in ambient air for which the instrument does not give a zero response
3.10
Expanded uncertainty
for the purposes of this standard, the combined uncertainty of the measurement multiplied by a factor
of 2 and so expressed with a level of confidence of 95 %
3.11
Independent measurement
individual measurement that is not influenced by a previous individual measurement
3.12
Individual measurement
measurement averaged over a time period equal to the sampling time
3.13
Influence quantity
quantity that affects the result of a measurement
3.14
Interference
response of the analyser to interferents
3.15
Interferent
single gaseous component in the sampled air, other than benzene, that affects the output signal of the
analyser
3.16
International (measurement) standard
standard recognised by an international agreement to serve internationally as the basis for assigning
values to other standards of the quantity concerned
3.17
Lack of fit
deviation of the average of a series of measurements at the same concentration from the linear
regression line
3.18
Limit value
concentration level fixed on the basis of scientific knowledge, with the aim of avoiding, preventing or
reducing harmful effects on human health, as stated in the EU legislation
3.19
Linearity
ability of a series of data to be modelled by a linear regression line
3.20
Long term drift
change in zero or span readings over the period of unattended operation
3.21
Measurand
particular quantity subject to measurement. For the purpose of this EN-standard it is benzene in air
3.22
Monitoring station
enclosure located in the field in which an automated benzene-analyser has been installed in such a
way that its performance and operation complies with the prescribed requirements
3.23
Operational range
concentration range for which the analyzer is calibrated. It shall not exceed the certification range
3.24
Parallel measurement
two measurements from different analysers, sampling from one and the same sampling manifold
starting at the same time and ending at the same time
3.25
Performance characteristic
one of the parameters assigned to equipment in order to define its performance, e.g. linearity
3.26
Performance criterion
limiting quantitative numerical value assigned to a performance characteristic, to which conformance is
tested
3.27
Repeatability (of results of measurement)
closeness of the agreement between the results of successive measurements of the same measurand
carried out under the same conditions of measurement [2]
NOTE 1 These conditions are called laboratory repeatability conditions and include:
- the same measurement procedure;
- the same analyser, used under the same conditions;
- at the same location;
- repetition over a short period of time;
- the same observer.
NOTE 2 In this EN-standard the repeatability is expressed as a value with a level of confidence of 95 %.
3.28
Response time
time interval between the instant when a stimulus is subjected to a specified abrupt change and the
instant when the response reaches and remains within specified limits around its final steady value.
NOTE For the analyzers described in this Standard, that perform measurements integrated over a certain
time period, the response time is at least one measurement cycle.
3.29
Reproducibility under field conditions
closeness of the agreement between the results of parallel measurements with two analysers in
ambient air carried out under the same conditions of measurement
NOTE 1 These conditions are called field reproducibility conditions and include:
- the same measurement procedure;
- two identical analysers, used under the same conditions;
- at the same monitoring station;
- the period of unattended operation.
NOTE 2 In this EN-standard the reproducibility under field conditions is expressed as a value with a level of
confidence of 95 %
3.30
Sampled air
ambient air that has been sampled through the sampling inlet and sampling system
3.31
Sampling inlet
entrance to the sampling system where the ambient air is collected from the atmosphere
3.32
Short term drift
change in zero or span measurement results over a 24 hour period
3.33
Sorbent
materials that can collect benzene from sample air with near 100 % efficiency and release it again by
heating in a flow of a carrier gas e.g. nitrogen, helium or hydrogen
3.34
Standard uncertainty
uncertainty of the result of a measurement expressed as a standard deviation [ENV 13005:1999]
3.35
Temperature of surrounding air
temperature of the air directly surrounding the analyser, ie the temperature inside the monitoring
station or laboratory
3.36
Transfer standard
working standard that is routinely used to calibrate or check measuring instruments and is traceable to
an international standard and can be moved (transferred) from place to place
3.37
Type approval
decision taken by a designated laboratory that the pattern of an analyser conforms to the requirements
as laid down in this EN-standard (comparable to the "pattern approval" as described by the OIML [4])
3.38
Type approval test
examination of two or more analysers of the same pattern which are submitted by a manufacturer to a
designated body; this examination includes the test necessary for approval of the pattern (comparable
to "pattern evaluation" as described by the OIML [4])
3.39
Uncertainty
parameter associated with the result of a measurement that characterises the dispersion of the values
that could reasonably be attributed to the measurand
4 Symbols and abbreviated terms
A  intercept of the calibration function
A availability of the analyser
a
B  slope of the calibration function
bj  sensitivity coefficient of c for influence quantity xj at C = ctest
c  measured value of the measurand
ctest  value of the measurand at which the required measurement uncertainty is given
c  average value of individual measurements of the measurand
d drift of measured value on input quantity Yi at C = ctest
E collection efficiency of sample system
ss
i  index of input quantities Y
j  index of influence quantities X
k  coverage factor
n  total number of input quantities; last number
m  total number of influence quantities
p  index of the performance characteristic
pmax maximum number of performance characteristics considered
r Repeatability
s(xj)  standard deviation of xj at C = ctest
t0,95 95 percentile of the t-distribution
Uc  combined expanded uncertainty of c at C = ctest expressed as a 95 % confidence interval
uc combined standard uncertainty of c at C = ctest
u partial standard uncertainty of c due to repeatability of input quantity Yi at yi
r
corresponding to C = ctest
u partial standard uncertainty of c due to reproducibility of input quantity Yi at yi
R
corresponding to C = ctest
u standard uncertainty of input quantity Yi
x jth influence quantity
j
X  lack of fit
l
y  individual measurand
i
Y carry over or memory effect of measurand
5 Principles
A measured volume of sample air is drawn or forced through a sorbent tube. Provided suitable
sorbents are chosen, benzene is retained by the sorbent tube and thus is removed from the flowing air
stream. The collected benzene (on each tube) is desorbed by heat and is transferred by inert carrier
gas into a gas chromatograph equipped with a capillary column and a flame ionisation detector or
other suitable detector, where it is analysed. Prior to entering the column the sample is concentrated
either on a cryo trap, which is heated to release the sample into the column, or on a pre-column,
where higher boiling hydrocarbons are removed from the pre-column by back flush.
Two general types of instruments are used. One is equipped with a single sampling trap and the other
is equipped with two or more traps. The single trap instrument samples for only part of the time in
each cycle whereas the multitrap instrument samples continuously as illustrated in Figures 1 and 2
respectively. Typical cycling times are between 15 minutes and 1 hour.

Figure 1 sampling by single trap
Figure 2 sampling by multitrap

6 Reagents and materials
6.1 Measurement standards of Benzene
Standard atmospheres of known concentrations of benzene shall be prepared by recognised
procedures as described in ISO 6142, ISO 6144 and ISO 6145. If the procedure is not applied under
conditions that will allow the establishment of full traceability of the generated concentrations to
standards of mass or volume, or if the chemical inertness of the generation system cannot be
guaranteed, the concentrations need to be confirmed using an independent procedure or a reference
gas traceable to national standard.
The concentrations of measurement standard atmospheres shall have an expanded uncertainty of
less than 5%.
An internationally accepted certified matrix reference material may also be used.
6.2 Transfer standard/span gas
A transfer standard is needed for quality control to check the regular function of the analyser and to
allow correction of drift. The concentration needs to be known but traceability can be obtained from the
standard atmospheres of 6.1. The benzene concentration should be between 70% and 90% of the
certification range. Transfer standards have to be stable during the period of usage.
The concentrations of transfer standard atmospheres shall have an expanded uncertainty of less than
7,5%.
Methods for transfer standard preparation are listed in Table 1.

Table 1 - Methods for preparation of transfer standards
Method Description Traceability/
Standard to be used
Gravimetry Gas cylinder with a content of benzene in the range 70%-90% of the ISO 6142
certification range ISO 6143
Permeation tubes Mass loss of benzene from a permeable tube into a zero air stream ISO 6145-10
Dynamic dilution Dynamic blending of cylinder gas containing high benzene ISO 6145-7
concentration (mg/m³) with zero air
Diffusion Mass loss of benzene from a diffusion tube into a zero air stream ISO 6145-8

NOTE Practical examples of the application of these methods, with performance characteristics, are
described in VDI 2100 Part 4 [5].
6.3 Zero air
Zero air shall have a content of benzene lower than the detection limit and can be provided either as
synthetic air from a cylinder or from a compressor followed by an air purifier system.
NOTE The chromatograms of zero air samples provide a check of the benzene content. Where available an
independent measurement method should be used for purity analysis.
7 Apparatus
Some typical automated gas chromatograph systems, with their operational parameters for trapping,
focusing trap/pre-column, capillary column and detectors are listed in Annex D.
The following equipment is also needed.
7.1 Calibration facility
Calibration standards shall be traceable to internationally accepted standards and meet the
requirements of 6.1 and 6.2.
7.2 Sample inlet, sample line and filter
The sampling line and the residence time of the sample shall be as short as practicable. The line and
the filter shall be chemically inert to benzene, made of a material such as glass, stainless steel or Per-
Fluoro-Carbon (FEP or PFA). Calibration or span gases shall be used to test the inertness of the
complete sampling train. The influence of the sample line, filter and inlet shall be less than 2% of the
signal output of the analyser at a concentration close to the Limit Value.
NOTE The sample line may need to be moderately heated to avoid condensation of water. Condensation
may occur in the case of high ambient temperature and/or humidity.

8 Type approval
8.1 Introduction
Type approval of an analyser requires provision of evidence that the requirements concerning data
quality specified by the applicable EU Directive, 2000/69/EU, will be met when the analyser is used in
all conditions typical of its intended use.
Type approval testing, by designated bodies, is the quantified assessment of the performance
characteristics given in this standard as necessary to achieve a measurement uncertainty less than or
equal to the required uncertainty.
The performance characteristics are to be assessed by tests carried out in the laboratory with two
identical analysers, and in the field (monitoring site) with at least two identical analysers of the same
type out of one series. Both analysers are required to pass the test and all results shall be reported.
Appropriate experimental evidence shall be provided by
- type approval test results, and
- calculation of measurement uncertainty by reference to ENV 13005, to ISO 5725-2 or to both
documents.
8.2 Performance characteristics and performance criteria determined in laboratory
tests
The laboratory tests consist of the determination of the performance characteristics stated in Table 2,
according to the procedures described in 8.5.
NOTE It is recommended that the designated body for the type approval test shall be accredited for these
activities according to EN ISO/IEC 17025.
Table 2 - Relevant performance characteristics and performance criteria determined in
laboratory test
*No. Performance characteristics Symbol Paragraph **Performance
criterion
1 Lack of fit, largest residual X 8.5.3 < ± 5 %
l
3 3
2 Repeatability at 0,5 µg/m r 8.5.5 < ± 0,3 µg/m
(0,5)
3 Repeatability at limit value r 8.5.5 < ± 5 %
(LV)
4 Influence of the interference from ozone 8.5.9.1 < ± 5 %
b
O
5 Influence of the interference from sum of 8.5.9.3 < ± 5 %
b
C
org
possible interfering organic compounds at span
value
6 Influence of the interference from relative 8.5.9.2 < ± 4 %.
b
rh
humidity
7 Sensitivity coefficient for the influence of 8.5.7 < ± 0,2 %/K
b
Ts
surrounding temperature at span value
8 Sensitivity coefficient for the influence of 8.5.6 < ± 1 %/kPa
b
p
ambient pressure at span value
9 Sensitivity coefficient for the influence of 8.5.8 < ± 0,2 %/V
b
V
voltage at span value
10 Short term drift (24 hours) at span value 8.5.4 < ± 5 %
d
24h
12 Carry over Y 8.5.10 < 10 % of the limit
value for the first
analysis after the
response time
* Nos. 1 and 3-9 are used in calculation of combined uncertainty of a measured value
** Where the performance criterion is expressed as a percentage, the test value shall be calculated as 100 u/C, where u is the
-3
uncertainty component in µg m , as determined in the paragraph indicated in the table, and C is the highest benzene
-3
concentration used for the test, in µg m

8.3 Type approval assessment
For the purpose of type approval the analysers tested shall fulfil the following requirements:
a) each individual performance characteristic shall fulfil the criteria in Table 2 (laboratory tests) and
Table 5 (field tests, Section 8.6).
b) the expanded measurement uncertainty calculated from the combination of all performance
characteristics shall be less than the maximum allowable uncertainty prescribed in the relevant
Directive.
Sections 8.5.3 to 8.5.10 describe the laboratory type approval tests that determine the performance
criteria shown in Table 2. Performance characteristics noted in Table 2 (laboratory tests) and Table 5
(field tests) shall be included in the calculation of expanded uncertainty.
8.4 Changes in design
The manufacturer shall report any design change to a previously type approved monitor, including
software changes, to the competent authority. The underlying purpose of the design change and the
expected consequences with respect to the performance characteristics, as stated in Table 2 and
Table 5, shall be reported by the manufacturer. The competent authority [3] shall decide whether new
tests are necessary or not.
Changes to the following are excluded from this requirement:
- Materials in the instrument frame (housing);
- electronic connectors and slots;
- bolts, nuts, cable binders and other fixing materials.

8.5 Procedures for determining performance characteristics during laboratory tests,
and calculation of the standard uncertainties
8.5.1 Introduction
A designated body shall perform the determination of the performance characteristics in the laboratory
as a part of the type approval test. The quality of the materials and equipment used in the test
procedures shall be in accordance with the requirements given in this standard. The laboratory tests
shall be performed on two analysers.
8.5.2 Test conditions
8.5.2.1 General
Before operating the analyser, the manufacturer’s operating instructions shall be followed, particularly
with regard to installation, and the quality and quantity of necessary consumable items.
Before any tests are performed, the warm-up time specified by the manufacturer shall be taken into
account. If the warm-up time is not specified, a minimum of two hours shall be assumed.
All tests shall be performed in a time schedule that is as short as possible, to minimise the influence of
drift and changes in ambient conditions.
When applying test gases to the analyser, the test gas system shall be operated for a sufficient time to
stabilise the concentration.
8.5.2.2 Accommodation and environmental conditions
The laboratory shall ensure that environmental conditions such as ambient temperature and power
supply do not adversely affect the quality of any results.
The environmental conditions and all test conditions shall be monitored, controlled and recorded as
required by the relevant specifications.
Limiting conditions for the laboratory type approval tests are given in Table 6, in section 8.8.
8.5.2.3 Calibration gases
Several laboratory tests require calibration gases (air containing a known amount of benzene) to be
used. These shall be traceable to national standards unless otherwise stated in this EN-standard.
Various methods for the generation of calibration gases are given in Table 3.
Table 3 - Methods for preparation of primary calibration gases
Method Description Traceability/
Standard to be used
Gravimetry Gas cylinder with a content of benzene in the range of a few ppb ISO 6142
Permeation tubes Determination of the weight loss of a permeable tube containing ISO 6145-10
benzene
Static dilution Preparation by means of injecting known amounts of benzene ISO 6144
into a known volume of diluent gas
Dynamic dilution Dynamic blending of cylinder gas with synthetic air ISO 6145-7
Diffusion Preparation using diffusion tubes ISO 6145-8

8.5.3 Lack of fit
A linear regression function is determined from the responses of the analyser and the corresponding
applied concentration levels. The residual at each concentration level is equal to the difference
between the average response measured, expressed as a concentration, and the concentration given
by the linear regression function.
The linearity of the analyser shall be tested over the range between 0 % and 90 % of the maximum of
the certification range, using at least six concentrations (including the zero point). The following
3 3 3
concentrations shall be used: 0 (below the detection limit); 5 µg/m ± 10%; 15 µg/m ± 10%; 25 µg/m ±
3 3
10%; 35 µg/m ± 10% and 45 µg/m ± 10%. The calibration function for the analyser is evaluated from
the linearity test. At each concentration (including zero) at least 6 independent measurements shall be
performed. The first measurement at each concentration level shall be excluded from the data
analysis.
The uncertainty of the dilution ratios leading to the applied concentrations shall be less than ±1%.
The calculation of the linear regression function and residuals shall be performed according to
Annex A.
The largest relative residual from the linear regression function shall meet the criterion stated in Table
2.
When one or more of the relative residuals does not meet the above criterion, then the analyser does
not pass the linearity test.
The largest value of (d ) is reported as X and shall be included in the uncertainty calculation.
r c fit
The standard uncertainty due to lack of fit at the limit value, u is calculated according to:
fit,LV
u = ((X /100) × c ) / 3 (1)
fit,LV fit LV
where
u is the standard uncertainty due to lack of fit at the limit value;
fit, LV
X is the calculated residual from a linear regression function at the limit value (%)
fit,LV
(calculated according to Annex A);
c is the limit value.
LV
8.5.4 Short-term drift
The instrument shall be kept running under laboratory conditions whilst analysing span gas. From 4
successive measurements the mean value is calculated. After a period of 24 hours the measurements
at span value are repeated.
The short-term drift at span level is calculated as follows:
c − c
n n−1
d = ×100% (2)
24h
cn
where
d is the drift at span concentration c as percentage ;
t
24h
c is the average of the 4 analyses at the beginning of the drift period
n
cn−1 is the average of the 4 analyses at the end of the drift period (24 hours)
d shall comply with the performance criterion in Table 2.
24h
The uncertainty u due to short term drift shall be calculated as follows in accordance with ENV 13005:
s
c − c
n n−1
u = (3)
s
2 3
where
c is the average of the 4 analyses at the beginning of the drift period
n-1
c is the average of the 4 analyses at the end of the drift period (24-hours)
n
The result of the short term drift is not included in the uncertainty but is carried out to ensure that the
contribution is not important.
8.5.5 Repeatability
The standard deviations of 10 successive individual measurements at the limit value, and at
approximately 1/10 of the limit value, are calculated according to Equation 4:
()c − c
∑ testi test
s (c) = (4)
r
n −1
where
s (c) is the repeatability standard deviation at the measurand level c;
r
th
c is the i individual measurement at measurand level c ;
testi test
c is the average of the individual measurements at measurand level c ;
test
test
n is the number of individual measurements.
) is calculated according to:
The repeatability (r
i
r = t × s (5)
i n-1; 0,05 i
where
t is the two-sided Student's t-factor at a confidence level of 0,05, with n-1 degrees of
n-1, 0,05
freedom (for n = 10, t = 2,262);
9, 0,05
s is the repeatability standard deviation (µmol/mol).
l
r shall comply with the performance criterion in Table 2, both at zero and at the test concentration c
l t
(limit value).
The repeatability standard uncertainty u is determined by:
r
u = s (6)
r r
8.5.6 Dependence on sample gas pressure
Independent measurements shall be performed with concentrations at the limit value and sample gas
pressures of 80 kPa and 110 kPa. At each pressure at least four individual measurements shall be
made. From these measurements the averages at each pressure are calculated. The partial standard
uncertainty due to pressure changes u shall be estimated from:
P
b ⋅ ∆P
p
u = (7)
P
2 3
where the sensitivity coefficient b ((µg/m )/kPa) is given by
p
()c − c
P max P min
b = (8)
P
∆P
and
c is the average of the individual measurements at maximum sampling gas pressure P at
Pmax max
limit value concentration ;
c is the average of the individual measurements at minimum sampling gas pressure P at
Pmin min
limit value concentration
∆P = P - P (9)
max min
8.5.7 Dependence on surrounding air temperature
The influence of the surrounding air temperature shall be determined at the minimum and maximum
temperature specified by the manufacturer as the operating range for the analyser.
The influence shall be determined at approximately 1/10 of the limit value and at a span concentration
in the range of 70 % to 90 % of the maximum of the certification range. At each temperature setting at
least 4 individual measurements for each concentration shall be performed.
The criteria for warm-up or stabilisation time, according to section 8.5.2.1, shall be met at each
temperature.
The uncertainty caused by changes in surrounding temperature u is then determined
Ts
b ⋅ ∆T
T s
s
u = (10)
Ts
2 3
where the sensitivity coefficient b ((µg/m )/K) is given by
Ts
c − c
T ,max T ,min
s s
b = (11)
T
s
∆T
s
and
c is the average of the individual measurement at maximum surrounding temperature T ;
Ts,max s,max
c is the average of the individual measurement at minimum surrounding temperature sT
Ts,min min
∆T = T – T (12)
s s,max s,min
NOTE For these tests a climate chamber is necessary.
8.5.8 Dependence on voltage
The dependence on line voltage shall be determined by tests at the minimum and maximum of the
voltage range specified by the manufacturer, V and V . The benzene concentrations shall be
min max
approximately 1/10 of the limit value and around 70 % to 90 % of the maximum of the certification
range. At least 4 individual measurements at each voltage level and concentration shall be taken.
The uncertainty from voltage dependence u is calculated from:
V
b ⋅ ∆V
v
u = (13)
V
2 3
where the sensitivity coefficient b ((µg/m )/V) is given by
T
c − c
v max v min
b = (14)
v
∆V
and
c is the average of the individual measurement at maximum voltage V ;
Vmax max
c is the average of the individual measurement at minimum voltage V ;
Vmin min
∆V = V - V (15)
max min
8.5.9 Interference
8.5.9.1 General
The analyser response to certain interferents, which are to be expected to be present in ambient air,
shall be tested. The interferents can have a positive or negative effect. The test shall be performed at
benzene concentrations of 1/10 of the limit value and at 70 % to 90 % of the maximum of the
certification range.
The concentration of interferent gases in the test mixtures shall have an uncertainty of less than 10 %
and shall be traceable to national standards. The interferents to be tested and their respective
concentrations are given in 8.5.9.2, 8.5.9.3, and 8.5.9.4. The influence of each interferent shall be
determined separately. A correction to the concentration of the measurand shall be made for the
dilution effect due to addition of the interferent.
The influence of the interferences shall comply with the performance criteria in Table 2 Relevant
performance characteristics and performance criteria determined in laboratory test.
8.5.9.2 Ozone
The influence of ozone is checked by adding approximately 180 µg/m O to a standard atmosphere of
benzene at span concentration.
The influence quantity of ozone b is calculated as follows:
O
c − c
O
b = (16)
O
c
int,O
c − c
c O
int,O
u = b = (17)
O O
3 3
2 3
and
c is the average of the individual measurements at maximum ozone concentration C ;
O int,O3
c is the average of the individual measurement without ozone.

8.5.9.3 Relative humidity
The influence of relative humidity shall be checked at 20% and 80% relative humidity at standard
temperature and pressure and the relative uncertainty contribution u (C ) is calculated from:
test
rh
b
rh
u = (18)
rh
2 3
where the influence of humidity b ((µg/m )/%rh) is given by:
rh
c − c
rh,max rh,min
b = *100% (19)
rh
()c + c / 2
rh,max rh,min
and
c  is the average of the individual measurements at maximum relative humidity c ;
rh,max int,rh,max
c is the average of the individual measurement at minimum relative humidity c ;
rh,min int,rh,min
8.5.9.4 Organic compounds
Possible interference from organic compounds shall be investigated by a gas mixture of the organic
compounds listed in Table 4 at known concentrations of about 3-10 µg/m for each compound.
Table 4 - Possible interfering compounds
Compound
methylcyclopentane
2,2,3-trimethylbutane
2,4-dimethylpentane
tetrachloromethane
cyclohexane
2,3-dimethylpentane
2-methylhexane
3-ethylpentane
trichlorethylene
n-heptane
The relative uncertainty from interference of the sum of organic compounds u is calculated from;
C
org
c org − c
u = (20)
C
org
where the influence b is given by:
org
c − c
org
b = (21)
org
c
and
c is the average of the individual measurements in the presence of the gas mixture
org
selected;
c is the average of individual measured concentrations without interference.
NOTE The test in 8.5.9.4 does not strictly follow the method for estimating uncertainty in EN ISO 14956,
where interferences from compounds have to be calculated individually. However, the matrix effect of organic
compounds may be very important and the test on a mixture of all the compounds in Table 4 gives a better
uncertainty estimate.
8.5.10 Carry-over (memory effect)
During the linearity test the influence of a memory effect caused by the retention of benzene in the
measuring system due to inappropriate materials or a large dead volume is checked.
The second analysis of zero air immediately following analysis of the highest concentration of benzene
required for the linearity test shall not exceed a measured benzene concentration of 10% of the limit
value (= 0,5 µg/m³).
NOTE The value of every first analysis of the zero air measurements should be below 20% of the limit value
(=1 µg/m³). Due to the sampling procedure it is not possible to determine the response time exactly, and
according to the definitions the response time is at least one analysis cycle. Therefore the first analysis after an
abrupt concentration change cannot be taken into account. Evaluation of this test indicates only the suitability of
the measurement system.
The analysers have to fulfil the requirement stated in Table 2. In this case the contribution to the
uncertainty budget is considered to be negligible.
8.6 Procedures for determining performance characteristics during field tests
8.6.1 Introduction
In the field test, analysers shall be tested for availability, maintenance interval, reproducibility and long
term drift over a period of 3 months. Two analysers shall be run in parallel, sampling from a common
manifold, at a monitoring station selected for specific ambient air conditions (see section 8.6.3).
Operational requirements for the determination of long-term drift and reproducibility are given in
section 8.6.4.
8.6.2 Performance characteristics and performance criteria determined in field tests
Field tests shall be performed by a designated body according to the procedures described in Section
8.6. The performance characteristics given in Table 5 shall be determined.
Table 5 - Relevant performance characteristics and performance criteria determined in field
test
No. Performance characteristics Symbol paragraph Performance
criterion
1 *Reproducibility standard deviation 8.6.8 < ± 0,25 µg/m
s
Rf
2 *Long-term drift, at span value over 14 8.6.5 < ± 10 %
d
14d
days
3 Maintenance interval 8.6.6 >14 d
4 Availability 8.6.7 > 90%
A
a
*Parameters used for the uncertainty calculation

8.6.3 Selection of the field site
The selection of a monitoring station for the field test is based on the following criteria:
Location
- Urban, 4m to 5m from kerbside
Monitoring station facilities
- Sufficient capacity of the sampling manifold
- Enough room for two analysers together with calibration gases
- Surrounding air temperature control for the analysers
Other items that could be considered
- Telemetry/telephone facilities for remote surveillance of the functioning of the equipment
- Accessibility
8.6.4 Operational requirements
The correct functionality of the analysers shall be tested after their installation at the monitoring station.
This includes checks on the connections to the sampling manifold, sample gas flows, temperatures,
data transmission and any other items judged necessary by the designated body.
After verification of the proper functioning of the analysers, the response factors shall be checked with
a span value gas mixture with a concentration between 70% and 90 % of the maximum of the
certification range. During the 3 month period, the maintenance requirements by the manufacturer of
the analyser shall be followed.
For the first 14 days, measurements with span gases shall be performed at least every two days. The
span gas shall have a concentration between 70% and 90 % of the maximum of the certification range.
At least four independent, successive measurements shall be performed. The results shall be
recorded. For the remainder of the trial, measurements with span gases shall be performed at least
every two weeks.
For the duration of the field test, no zero and span adjustments shall be made to the analyser as this
will inf
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