Ambient air quality - Standard gravimetric measurement method for the determination of the PM2,5 mass fraction of suspended particulate matter

This European Standard describes a standard method for determining the PM2,5 mass concentration of suspended particulate matter in ambient air by sampling the particulate matter on filters and weighing them by means of a balance.
Measurements are made over a sampling period of about 24 h, and in line with the Directive, are expressed as µg/m3, where the volume of air is the volume at ambient conditions near the inlet at the time of sampling.
The range of application of the standard is from 1 µg/m3 (i.e. the limit of detection of the standard measurement method expressed as its uncertainty) up to 120 µg/m3 (i.e. the maximum concentration level observed during the field study undertaken by CEN/TC 264/WG 15 to validate the standard).
NOTE    Although the standard is not validated for concentrations over 120 µg/m3, its range of application could well be extended to commonly encountered ambient concentrations up to circa 200 µg/m3 when using glass or quartz fibre filters. At these high concentrations and particulate mass loadings no filter clogging is to be expected. Also the flow rate can be easily maintained at the nominal setting.
The equivalence procedure in Annex A specifies two approaches, depending on whether the candidate method differs slightly or fundamentally from the standard method.
In the former case, involving only slight differences from the standard method ("variations on a theme") Annex A provides a restricted procedure to compare only the pertinent differences, instead of a full field test. This part of the annex serves to give practical guidance for determining equivalence for measurement methods commonly used in monitoring networks, and includes examples of common variations to the standard method, such as different filter storing or conditioning procedures and the variation of the standard method for the application as automated filter changer.

Luftbeschaffenheit - Gravimetrisches Standardmessverfahren für die Bestimmung der PM2,5-Massenfraktion des Schwebstaubs

Diese Europäische Norm beschreibt ein Standardmessverfahren zur Bestimmung der PM2,5-Massenkonzen-
tration des Schwebstaubs in der Außenluft. Die Probenahme des Staubes erfolgt auf Filtern und durch
Wägung der Filter mit Hilfe einer Waage.
Die Messungen werden über eine Probenahmedauer von etwa 24 h durchgeführt. Die Ergebnisse werden
gemäß der EU-Richtlinie in µg/m 3 ausgedrückt, wobei das Luftvolumen auf das Volumen bei Umgebungs-
bedingungen nahe dem Probenahmekopf zur Zeit der Probenahme bezogen wird.
Der Anwendungsbereich dieser Europäischen Norm liegt zwischen 1 µg/m 3 (das heißt die Nachweisgrenze
des Standardmessverfahrens ausgedrückt als deren Unsicherheit) bis zu 120 µg/m 3 (das heißt die maximale
Konzentration, die während der von der CEN/TC 264/WG 15 durchgeführten Feldprüfungen auftrat, um diese
Europäische Norm zu validieren).

Qualité de l'air ambiant - Méthode normalisée de mesurage gravimétrique pour la détermination de la fraction massique MP2,5 de matière particulaire en suspension

La présente Norme européenne décrit une méthode normalisée pour déterminer la concentration massique MP2,5 de matière particulaire en suspension dans l'air ambiant, en prélevant la matière particulaire sur des filtres et en pesant au moyen d'une balance.
Les mesurages sont effectués sur une période de prélèvement d'environ 24 h et, conformément à la Directive, ils sont exprimés en µg/m3, le volume d'air étant le volume dans les conditions ambiantes mesuré à proximité de l'orifice d'entrée au moment du prélèvement.
L'étendue de l'application de la norme va de 1 µg/m3 (c'est-à-dire la limite de détection obtenue avec la méthode de mesurage de référence, exprimée comme étant l'incertitude) jusqu'à au moins 120 µg/m3 (c'est à-dire le niveau de concentration maximal observé pendant l'étude in situ réalisée par le CEN/TC 264/GT 15 pour valider cette norme).
NOTE   Bien que la norme ne soit pas validée pour des concentrations supérieures à 120 µg/m3, son étendue d'application pourrait très bien s'étendre à des concentrations ambiantes courantes jusqu'à environ 200 µg/m3 quand on utilise des filtres en fibre de verre ou de quartz.
La procédure d'équivalence de l'Annexe A spécifie deux approches, selon que la méthode candidate est légèrement ou fondamentalement différente de la méthode normalisée.
Dans le premier cas, faisant état seulement de légères différences par rapport à la méthode normalisée (" variations d'un thème "), l'Annexe A fournit une méthode restreinte pour comparer uniquement les différences pertinentes, au lieu d'un essai in situ complet.

Kakovost zunanjega zraka - Standardna gravimetrijska metoda za določevanje masne frakcije PM2,5 lebdečih delcev

General Information

Status
Withdrawn
Publication Date
06-Sep-2005
Withdrawal Date
20-May-2014
Current Stage
9960 - Withdrawal effective - Withdrawal
Due Date
21-May-2014
Completion Date
21-May-2014

RELATIONS

Buy Standard

Standard
EN 14907:2005
English language
29 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN 14907:2005
01-december-2005
.DNRYRVW]XQDQMHJD]UDND6WDQGDUGQDJUDYLPHWULMVNDPHWRGD]DGRORþHYDQMH
PDVQHIUDNFLMH30OHEGHþLKGHOFHY

Ambient air quality - Standard gravimetric measurement method for the determination of

the PM2,5 mass fraction of suspended particulate matter

Luftbeschaffenheit - Gravimetrisches Standardmessverfahren für die Bestimmung der

PM2,5-Massenfraktion des Schwebstaubs
Qualité de l'air ambiant - Méthode normalisée de mesurage gravimétrique pour la

détermination de la fraction massique MP2,5 de matiere particulaire en suspension

Ta slovenski standard je istoveten z: EN 14907:2005
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
SIST EN 14907:2005 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 14907:2005
---------------------- Page: 2 ----------------------
SIST EN 14907:2005
EUROPEAN STANDARD
EN 14907
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2005
ICS 13.040.20
English Version
Ambient air quality - Standard gravimetric measurement method
for the determination of the PM2,5 mass fraction of suspended
particulate matter

Qualité de l'air ambiant - Méthode de mesurage Luftbeschaffenheit - Gravimetrisches

gravimétrique de référence pour la détermination de la Standardmessverfahren für die Bestimmung der PM2,5-

fraction massique PM 2,5 de matière particulaire en Massenfraktion des Schwebstaubs

suspension
This European Standard was approved by CEN on 22 July 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 14907:2005: E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
Contents page

Foreword ..........................................................................................................................................................3

Introduction......................................................................................................................................................4

1 Scope ...................................................................................................................................................5

2 Normative references .........................................................................................................................5

3 Terms, definitions and abbreviations................................................................................................6

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

3.2 Abbreviations ......................................................................................................................................6

4 Principle...............................................................................................................................................7

4.1 Description of the standard measuring principle.............................................................................7

4.2 Description of QA/QC procedures.....................................................................................................7

5 Equipment and facilities.....................................................................................................................8

5.1 Sampling system components ..........................................................................................................8

5.2 Weighing facilities.............................................................................................................................13

6 Sampling and weighing procedure..................................................................................................13

6.1 General ..............................................................................................................................................13

6.2 Weighing room procedures..............................................................................................................13

6.3 Unloaded filter weighing...................................................................................................................14

6.4 Sampling period................................................................................................................................14

6.5 Sample storage and transport procedures .....................................................................................14

6.6 Loaded filter weighing ......................................................................................................................15

7 Additional quality assurance and quality control...........................................................................15

7.1 General ..............................................................................................................................................15

7.2 Maintenance of the sampling system..............................................................................................15

7.3 Calibration .........................................................................................................................................15

7.4 Field blanks .......................................................................................................................................16

8 Expression of results........................................................................................................................16

9 Performance characteristics of the method....................................................................................16

9.1 General ..............................................................................................................................................16

9.2 GUM concept.....................................................................................................................................17

9.3 Individual uncertainty sources ........................................................................................................18

9.4 Expanded uncertainty vs. EU Data Quality Objectives ..................................................................24

Annex A (informative) Equivalence test procedure for non-standard measurement methods ..............25

A.1 General ..............................................................................................................................................25

A.2 Formal procedures............................................................................................................................25

A.3 Overview of test procedure..............................................................................................................26

Annex B (normative) Data-quality objectives (source: Annex VIII of [2])..................................................27

Annex ZA (informative) Relationship with EU Directives ..........................................................................28

Bibliography...................................................................................................................................................29

---------------------- Page: 4 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
Foreword

This European Standard (EN 14907:2005) 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 March 2006, and conflicting national standards shall be withdrawn at

the latest by March 2006.

This European Standard 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(s).

For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this European

Standard.

As part of a continuous quality improvement, it is anticipated that this standard and EN 12341 (PM ) may be

reviewed by the Technical Committee in the near future.

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.
---------------------- Page: 5 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
Introduction

For air quality across the European Union to be assessed on a consistent basis, Member States need to

employ standard measurement techniques and procedures. The aim of this European Standard is to present a

harmonised methodology for monitoring the 2,5 µm mass fraction of suspended particulate matter (PM ) in

2,5

ambient air, following Community Directive 96/62/EC on ambient air quality assessment and management [1],

and Council Directive 1999/30/EC relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of

nitrogen, particulate matter and lead in ambient air [2], which sets the parameters specific to the assessment of

particulate matter.

The standard method set out in this European Standard is focused primarily on harmonisation and

improvement of the data quality of measurement methods used in monitoring networks, but is not necessarily

best suited for practical use in routine monitoring.

There are no traceable reference standards for PM measurements. Therefore, the standard method set out

2,5

in this European Standard defines the measured quantity by convention, specifically by the sample inlet

design and associated operational parameters covering the whole measurement process. The standard

contains:
 manual gravimetric standard measurement method for PM using single filters;
2,5

 summary of performance characteristics of the method, including measurement uncertainty;

 procedure for determining whether non-standard measurement methods (like other manual gravimetric or

automatic monitoring methods) are equivalent to this standard method (Annex A).

The precision and performance characteristics described in this European Standard were determined in 9

different comparative and validation trials. The trials were performed at 9 different sites in northern, middle

and southern European countries in order to cover a wide range of relevant ambient air conditions. The trials

were sponsored by the European Commission and the European Free Trade Association.

In addition to the measurement procedure of the 2,5 µm mass fraction of suspended particulate matter (PM )

2,5

in ambient air being described in this European Standard, there is European Standard EN 12341 [3] dealing

with the measurement of PM .
---------------------- Page: 6 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
1 Scope

This European Standard describes a standard method for determining the PM mass concentration of

2,5

suspended particulate matter in ambient air by sampling the particulate matter on filters and weighing them by

means of a balance.

Measurements are made over a sampling period of about 24 h, and in line with the Directive, are expressed

as µg/m , where the volume of air is the volume at ambient conditions near the inlet at the time of sampling.

The range of application of the standard is from 1 µg/m (i.e. the limit of detection of the standard

measurement method expressed as its uncertainty) up to 120 µg/m (i.e. the maximum concentration level

observed during the field study undertaken by CEN/TC 264/WG 15 to validate the standard).

NOTE Although the standard is not validated for concentrations over 120 µg/m , its range of application could well be

extended to commonly encountered ambient concentrations up to circa 200 µg/m when using glass or quartz fibre filters.

At these high concentrations and particulate mass loadings no filter clogging is to be expected. Also the flow rate can be

easily maintained at the nominal setting.

The equivalence procedure in Annex A specifies two approaches, depending on whether the candidate

method differs slightly or fundamentally from the standard method.

In the former case, involving only slight differences from the standard method (“variations on a theme”) Annex

A provides a restricted procedure to compare only the pertinent differences, instead of a full field test. This

part of the annex serves to give practical guidance for determining equivalence for measurement methods

commonly used in monitoring networks, and includes examples of common variations to the standard method,

such as different filter storing or conditioning procedures and the variation of the standard method for the

application as automated filter changer.

In the latter case, involving a full set of field tests, the procedure serves to determine equivalence only within

the range of conditions under which the field tests are carried out. The equivalence can be shown to hold for

conditions prevailing within European countries by carrying out the field test in situations covering a suitable

range of relevant ambient parameters (such as concentration and composition of the suspended particulate

matter, temperature, and humidity).

Although this European Standard does not explicitly address automatic monitoring methods for the

measurement of the PM mass fraction in ambient air, the equivalence test procedure in Annex A applies

2,5
both to non-automatic and automatic methods.
2 Normative references

The following referenced documents are indispensable for the application of this European Standard. 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 measurements

CR 14377, Air quality – Approach to uncertainty estimation for ambient air reference measurement methods

---------------------- Page: 7 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
3 Terms, definitions and abbreviations

For the purposes of this European Standard, the following terms, definitions and abbreviations apply.

3.1 Terms and definitions
3.1.1
ambient air
outdoor air in the lower troposphere excluding workplace air
3.1.2
PM automatic monitoring method
2,5

method intended for the automatic on-line determination of the PM mass concentration of suspended

2,5
particulate matter in ambient air
3.1.3
high volume sampling method
HVS
method for sampling particulate matter with a flow rate of 30 m /h
3.1.4
low volume sampling method
LVS
method for sampling particulate matter with a flow rate of 2,3 m /h
3.1.5
2,5

fraction of suspended particulate matter which passes through a size-selective inlet with a 50 % cut-off efficiency

at 2,5 µm aerodynamic diameter

NOTE By convention, the size-selective standard inlet design prescribed in 5.1.2, used at the flow rate given in 5.1.5,

possesses the required characteristics in order to sample the PM fraction in ambient air.

2,5
3.1.6
suspended particulate matter
SPM
notion of all particles surrounded by air in a given, undisturbed volume of air
3.1.7
uncertainty (of measurement)

parameter, associated with the result of a measurement, that characterizes the dispersion of the values that would

reasonably be attributed to the measurand (see also ENV 13005)
3.1.8
nominal flow rate
flow rate at the point set
3.2 Abbreviations
3.2.1
candidate method (non-standard measurement method)
3.2.2
DQO
EU data quality objectives
3.2.3
particulate matter
---------------------- Page: 8 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
3.2.4
quality assurance
3.2.5
quality control
3.2.6
relative humidity
3.2.7
standard measurement method
3.2.8
SPM
suspended particulate matter
4 Principle
4.1 Description of the standard measuring principle

Ambient air is passed through a PM size-selective inlet, at a known, constant flow rate. The PM fraction is

2,5 2,5

collected on a filter for a known period of about 24 h. The mass of the PM material is determined by

2,5

weighing the filter at constant conditions before and after collection of the particulate matter.

Key factors which can affect the result of the measurement, and which are addressed by the procedures

prescribed within this European Standard, include:

 deposition losses of non-volatile PM fraction within the pipework between the inlet and the filter;

2,5

 uncontrolled losses due to volatilisation of semi-volatile PM , both within the pipework between the inlet

2,5
and the filter, and on the filter at any time between collection and weighing;

 possible changes in weight of the filters or PM fraction due to adsorbed water, spurious addition or loss

2,5
of material, buoyancy, or static electricity;
 flow rate.
4.2 Description of QA/QC procedures

The quality assurance/quality control (QA/QC) procedures within this European Standard are separated into

those activities typically carried out with each measurement, and those carried out less frequently.

QA/QC procedures which are used for each measurement, including filter handling and conditioning, weighing

room conditions, proper functioning of the weighing instrument, and the use of blank filters, are described in

Clause 6.

Additional QA/QC procedures which are used on a less frequent basis, including flow calibration, calibration of

the weighing instrument, and maintenance (inlet cleaning) and leak testing of the sampling system, are

described in Clause 7.
---------------------- Page: 9 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
5 Equipment and facilities
5.1 Sampling system components
5.1.1 General

This European Standard contains two different designs for the sampling system to be used within the standard

method. These designs operate at significantly different flow rates, and will be described throughout the text

as the "low volume" or LVS and "high volume" or HVS designs.

The sampling system for the standard measurement method consists of the following elements, illustrated

schematically in Figure 1.
---------------------- Page: 10 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
Key
1 Air sample (T , p )
a a
2 Impactor inlet
3 Connecting pipework
4 Sheath air (only LVS, see Note in 5.1.3)
5 Filter holder
6 Flow measuring device
7 Pump
8 Flow control system
9 Measurement of temperature T, pressure p and flow rate F
T Ambient temperature
p Ambient pressure
F Flow rate related to ambient conditions (T , p )
a a a
T ×p
F = (m /h)
T × p
Figure 1 – Scheme of PM standard sampler
2,5
 size-selective inlet, whose design is prescribed in 5.1.2;

 connecting pipework between the inlet and the filter holder, described in 5.1.3;

 filter holder and filter, described in 5.1.4;
 flow control system, given by performance specifications in 5.1.5.
---------------------- Page: 11 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)

The sampling system shall be made of an inert, non-corroding, electrically conducting material such as

preferably stainless steel or anodised aluminium or aluminium alloy.

Correct operation of the sampling system also requires calibration devices regarding flow rate, and ambient

temperature and pressure sensors, with specifications given in Clause 7.
5.1.2 Standard inlet design
5.1.2.1 General

The critical dimensions of the inlet designs for LVS and HVS are given below in 5.1.2.2 and 5.1.2.3

respectively.
5.1.2.2 LVS standard inlet design
All measures in millimetres
Tolerance of all measures without tolerances: ± 0,2 mm respectively ± 0,5 °
Key
1 Air sample
2 Drainage for impacted water
3 To filter
H7 Manufacturing tolerance
Figure 2 – Design of 2,3 m³/h PM LVS inlet
2,5
---------------------- Page: 12 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
5.1.2.3 HVS standard inlet design
All measures in millimetres
Tolerance of all measures without tolerances: ± 0,2 mm respectively ± 0,5 °
Key
1 Air sample
2 Drainage for impacted water
3 To filter
H7 Manufacturing tolerance
Figure 3 – Design of 30 m³/h PM HVS inlet
2,5
---------------------- Page: 13 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
5.1.3 Connecting pipework

The requirements for the connecting pipework between the inlet and the filter holder are to minimise

deposition losses of particulate matter by kinetic processes, as well as losses due to thermal, chemical or

electrostatic processes. Contact of the sampled air with cold surfaces which could cause condensation shall

be avoided.

Also, the pipework shall be designed to minimise the effect of solar heating so that the air sample is kept as

close as possible to ambient temperature.

The temperature of the connecting pipework should be kept close to the ambient temperature as close as

possible. The deviation of the temperature shall be less than ± 5 °C (preferably measured directly behind the

filter).

NOTE This requirement can be met for the LVS by flowing a sheath of ambient air around the pipework between the

inlet and the filter up to the close range of the filter. For the HVS, the high air velocity inside the connecting pipework is

generally sufficient to meet the requirement.

The flow velocity in the pipework, determined by the tube diameter, that prevents significant losses due to

diffusion or turbulent inertial impaction.
The pipework shall have no bends and be vertical.

The length of the connecting pipework between the inlet and the filter holder shall be no longer than 3 m.

The pipework shall be made of an inert, non-corroding, electrically conducting material preferably such as

stainless steel or anodised aluminium.
5.1.4 Filter holder and filter

The filter holder shall be made of an inert, non-corroding material such as stainless steel or anodised

aluminium. Plastic material such as polycarbonate, POM (polyoxymethylene) or PTFE

(polytetrafluoroethylene) can also be used.

The filter holder arrangement shall be designed in such a way that the temperature of the filter holder and the

filter are kept as close as possible to ambient temperature. The effect of heating sources such as solar

radiation and cooling elements such as electrical apparatus (e.g. the sampling pump), and air conditioning

shall be minimised. During warm seasonal periods e.g. in spring, summer and autumn the temperature rise of

the sample filter shall be limited to less than 5 °C measured above the temperature of the ambient air

surrounding of the sampler, by incorporating temperature measurements preferably directly downstream the

filter.

The filters shall be made of glass fibre, quartz fibre, PTFE or PTFE coated glass fibre.

The filters shall have a separation efficiency of at least 99,5 % at an aerodynamic diameter of 0,3 µm.

NOTE It is recommended that filter manufacturers determine the filter separation efficiency according to standard

methods such as EN 13274-7 [4] or EN 1822-1 [5].

For the LVS the filter holder shall be suitable for insertion of circular filters, such that the diameter of the free

area through which the sampled air passes shall be between 34 mm and 41 mm.

For the HVS the filter holder shall be suitable for insertion of circular filters, such that the diameter of the free

area through which the sampled air passes shall be between 135 mm and 143 mm.

The filter support shall be made either of stainless steel, polycarbonate, POM or PTFE grid material.

---------------------- Page: 14 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)
5.1.5 Flow control system

The flow system for sample collection shall provide the flow rate necessary for the correct size-selection at the

inlet, and also a known sampled volume for calculation of the PM concentration. The flow control system

2,5
shall be in accordance with basic physical principles.

As the sampled volume shall be expressed at ambient air conditions near the PM inlet, the flow control shall

2,5

be such that the sampled volume of air at ambient conditions per unit time is kept constant, by incorporating

temperature and pressure measurements at a representative location in ambient air. The flow rate measured

by the flow control system installed downstream of the filter being sampled shall be converted to ambient

conditions according to the ideal gas law.

Volumetric flow through the inlet shall be controllable to a nominal value of 2,3 m /h at ambient conditions for

the LVS standard inlet, and 30 m /h for the HVS reference inlet. The instantaneous value of the flow rate shall

be held constant within 5 % of the nominal value at ambient conditions.

The volumetric flow averaged over the measurement period shall be within 2 % of the nominal value.

This time duration can be determined using any timing device which provides the accuracy required in 6.4.

5.2 Weighing facilities

A climate-controlled facility shall be used for conditioning and weighing the filters. This facility will be referred

to within this European Standard as the "weighing room", though it may be either a suitable room or cabinet.

The temperature and the relative humidity shall be continuously monitored and controlled to 20 °C ± 1 K and

(50 ± 5) % RH respectively.

WARNING The weighing room conditions in 5.2 should refer to the conditions given in EN 12341. The WG

which drafted the standard strongly recommends that the relative humidity during conditioning shall be

lowered. For reasons of legal continuity it was decided that this would be best accomplished by linking

prEN 14907 to EN 12341 and reevaluating the parameters when EN 12341 is revised in the near future.

The balance used shall be installed and operated within the weighing room and have a resolution equal to or

better than 10 µg for filters used with the LVS system, equal to or better than 100 µg for filters used with the

HVS system.
6 Sampling and weighing procedure
6.1 General

This section covers the procedure to be followed for each measurement, including Quality Assurance and

Quality Control measures to be applied.
6.2 Weighing room procedures
The following procedures shall be applied at every weighing session:
Weighing room conditions shall be monitored and documented.
Filters shall always be handled with tweezers (stainless steel or PTFE-coated).

NOTE 1 When PTFE-coated tweezers are used, static charges can occur at fibre filters.

All filters shall be visually checked prior to use for defects such as holes or loose material, and discarded if

defects are found.

At the beginning of each weighing session the proper functioning of the balance shall be checked with

reference masses with similar mass to the filters, as a measure of accuracy and drift of the balance. If the

---------------------- Page: 15 ----------------------
SIST EN 14907:2005
EN 14907:2005 (E)

reading of the balance differs by more than 20 µg for LVS or 200 µg for HVS from the reference mass, the

situation shall be investigated and resolved before proceeding.
A static discharger shall be used on PTFE filters prior to weighing.
NOTE 2 A static discharger is not necessary with glass fibre or quartz filters.

Two blank reference filters of the same size and material as those used for the measurement shall be kept in

the weighing room. Their weight shall be recorded at each weighing session, as a measure of climatic

conditions affecting the weight of the LVS and HVS filters.

For the LVS design, if the masses of the blank reference filters have changed by less than 40 µg since the last

weighing session, their average mass shall be recorded, and weighing of LVS filters can proceed. If the

masses of the blank reference filters have changed by more than 40 µg, the situation shall be investigated

and resolved before proceeding.

For the HVS design, if the masses of the blank reference filters have changed by less than 500 µg since the

last weighing session, their average mass shall be recorded, and weighing of HVS filters can proceed. If the

masses of the blank reference filters have changed by more than 500 µg, the si
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.