What is new in the revised EN13725:2021 standard?

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42 003   On the 20th of November 2012 the first meeting took place of Working Group 2, tasked by CEN/TC274 “Air Quality” to revise EN 13725:2003 ‘Air Quality - Determination of odour concentration by dynamic olfactometry’.

   After 8 years of work and 17 meetings, the final draft of the revised standard is finally completed and submitted on May 31st 2021 for formal vote in the CEN Technical Committee 264 “Air Quality” in 2021. This paper lists the changes that will affect the practice of olfactometry in Europe, once this standard is published as EN 13725:2021.

Anton P. van Harreveld
Convenor CEN/TC264/WG41 & founder Odournet group


   Competing interests: The author has declared that no competing interests exist.

   Academic editor:  Carloz N. Díaz

   Content quality: This paper has been peer-reviewed by at least two reviewers. See scientific committee here

   Citation:  Anton P. van Harreveld, 2021, What is new in the revised EN13725:2021 standard?, 9th IWA Odour& VOC/Air Emission Conference, Bilbao, Spain, Olores.org.

   Copyright:  2021 Olores.org. Open Content  Creative Commons license. It is allowed to download, reuse, reprint, modify, distribute, and / or copy articles in olores.org website, as long as the original authors and source are cited. No permission is required from the authors or the publishers.

   ISBN: 978-84-09-37032-0

   Keyword: standardisation, olfactometry, odour ,emisión, monitoring

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   On the 20th of November 2012 the first meeting took place of Working Group 2, tasked by CEN/TC274 “Air Quality” to revise EN 13725:2003 ‘Air Quality - Determination of odour concentration by dynamic olfactometry’. After 8 years of work and 17 meetings, the final draft of the revised standard is finally completed and submitted on May 31st 2021 for formal vote in the CEN Technical Committee 264 “Air Quality” in 2021. This paper lists the changes that will affect the practice of olfactometry in Europe, once this standard is published as EN 13725:2021.


1. Introduction

   EN 13725 was initially published as EN 13725:2003 ‘Air Quality - Determination of odour concentration by dynamic olfactometry’, after the draft was completed by working group 2 'Dynamic Olfactometry' of the Technical Committee 264 'Air Quality' of the European Committee for Standardization (CEN).

   In the 17 years since the standard was introduced, experience was built up in the many olfactometry laboratories in Europe and worldwide in using this standard method, often under ISO17025 accreditation. The standard has been widely adopted in Europe. Outside Europe various countries introduced national standards based on EN 13725:2003 (Australia 2001, Chile 2010 and Colombia 2011).

   According to the internal regulations of CEN a standard is reviewed every 5 year to determine if revision is needed or if the standard continues to be fit for purpose until the next review. In 2012 the outcome of the systematic review of EN 13725 indicated the need for a revision. On May 31 st 2021 the revised final draft was submitted to CEN with a new title: EN13725:2021 ‘Stationary source emissions — Determination of odour concentration by dynamic olfactometry and odour emission rate.’ The formal vote by TC264 “Air Quality” is expected in 2021. Upon a positive voting outcome, the standard will undergo editorial checks, and will then be translated into German and French before publication.

   A great amount of work has been done by the members of WG2, which led to an increase of the number of pages from 74 to 125. A special word of gratitude goes to the experts who contributed their professional expertise to this work as volunteers. The aim of this paper is to summarize some of the key changes which will affect the practice of olfactometry in Europe, once this standard is published in 2021.

Changes implemented in the revision process of EN13725

   The changes as a result of the revision by CEN/TC264/WG2 ‘Olfactometry’ are listed in an Annex in the new standard, as shown in the table below.

(Sub)clase Title Technical change
1 Scope

The scope has been revised. The determination of emission rate from passive area sources has been excluded from the scope.
References to EN15259 and EN ISO 16911-1 have been added to the scope.
The following additional topic was included in the field of application:

c) the determination of the SROM value of secondary reference odorant gas reference materials, in mol;

The following additional topics have been excluded from the field of application:

6. direct olfactometry, including field olfactometry;
7. static olfactometry;
9. the determination of odour emission rate from volume sources, such as fugitive emissions from buildings;
10. the determination of odour emission rate from passive area sources.

2 Normative references The reference to standard ISO10780 was removed and replaced by EN ISO 16911-1.
The standards EN15259 and EN ISO 20988 were added to the normative references
3 Terms and definitions  Terms and definitions were categorised, adjusted, extended and in some cases based on more relevant references.
5 Principle of method Replaces former clause 4 'Principle of measurement'. Former clause 3.3 'Unit of measurement' was incorporated in the new clause 5, while the information provided in the notes was included in a new informative Annex L. A new subclause 5.2 'Odorant gas sampling' was added. A new sub-clause 5.3.2 'Procedure for establishing a robust estimated value of the secondary reference odour mass (SROM)' was added. The SROM concept was introduced to allow the usage of secondary reference odorants, traceable to the primary reference odorant n-butanol.
6 Apparatus and materials Modified text replaces former clause 6 'Material, gases and panel members'. The structure of the text has remained the same. In subclause 6.2.2 'Materials for sample equipment', the list of appropriate materials was modified by removing the material glass and adding titanium and aluminium (for sampling hoods and wind tunnels only). Stainless steel was modified into:
'5) stainless steel with the technical properties to avoid inadequate recovery (e.g. passivated stainless steel), in particular of H2S and reduced sulphur compounds'
6.3.1 Materials for sample container (bags) A requirement for testing alternative materials was added, based on a recovery criterion specified in new subclause 9.5.1
6.4.2 Odorant reference materiales Requirements for secondary odorant reference materials were added 
6.5.1 Construction of the olfactometer Criteria for recovery of odorants and the instrumental response time were added
6.6.1 Olfactometry rooms The recommended maximum temperature of 25ºC was removed. A minimum set point temperature of 21ºC was introduced. Upper and lower limit for relative humidity was introduced.
6.7.2 Selection of assessors on individual variability and sensitivity A new requirement was introduced that the ITE data used for panel qualification shall not be older than 12 months
6.7.3 Monitoring of panel members on individual variability and sensitivity The former content on this issue was moved to a separate subclause. The number of ITE values to be used for monitoring is now fixed to n=12. Additional guidance on managing panel composition based on monitoring data was added.
7 Performance characteristics and criteria Former clause 6 'Performance quality requirements' has been extended to 'Performance characteristics and criteria'. The option to use additional secondary reference materials with known SROM value was introduced. A more comprehensive assessment of uncertainty was added, in clause 10.2. This implies that the uncertainty of a laboratory can only be assessed according to the method stated in subclause 10.2. The former subclause 5.5 'Quality requirements for sampling equipment' has been deleted and replaced by a requirement to determine the dilution factor when sampling as outlined in subclause.
8 Measurement objective and measurement plan New clause replaces former annex J 'Sampling strategy'. The normative reference to EN15259 has been introduced here. The revised text also replaces the informative former Annex J.
9 Measurement procedure New clause has been added and replaces former annex A 'Working conditions and working platform for sampling'
9.1 Sampling Former subclause 7.2.1 'Sampling for direct olfactometry' was removed, as this topic was excluded from the scope.
9.1.1 Health and safety issues during sampling A normative reference to the requirements of EN15259 was introduced.
9.1.3 Sample collection method The subclause was revised. The requirement for an integrity test (leak test) was added. A procedure for bag conditioning was added. New subclauses were added: Sampling using the 'lung' method Direct sampling method for sources at positive pressure Direct sampling using an open bag only Direct sampling method using a pump
9.1.4 Pre-dilution during sampling This subclause was revised and extended.
The former requirement of calibration of dynamic dilution equipment using instrumental calibration was removed and replaced by the requirement to determine the emission factor in the sample using either flow measurements or concentration measurements of indicator gases, as outlined in subclause.
9.1.5 Transport and storage of odorant gas samples before analysis The text of the former subclause 7.3.3. was revised. The maximum storage time of 30 hours was maintained. However, guidance was included that the storage time for all samples should be similar, to avoid differences in the degree of sample degradation, which is progressive with time. The maximum temperature limit during storage and transformation was removed. Guidance on relative humidity during transport was introduced.
9.1.6 Sampling strategy This subclause replaces the former subclause 7.4 and Annex J.
9.2 Sampling of a point source This subclause is a new introduction in the standard.
9.3 Sampling or area sources This subclause is a new introduction in the standard.
9.4.2 Evaluation time and inter stimulus time The minimum interstimulus time interval of 30 s included in former subclause 8.2. was removed.
9.4.3 Number and order of presentations The requirements in the new subclause are more specific than those in the former subclause 8.3. The former subclause 8.5 was replaced by a note.
9.5 Occupational safety for sampling personel, assessors and olfactometry operators This is a new subclause, replacing former subclause 8.6. and normative former Annex A. The new subclause was introduced to provide a more comprehensive to risk assessment and health and safety measures to be observed for sampling staff, olfactometry operators and assessors.
9.6.1 Calculation of odour concentration of a sample Replaces former subclause 9.2., without significant modifications.
10 Quality assurance and quality control procedures This is a new clause which has been added.
10.1 Field blank This new subclause states the requirements for ensuring that no significant contamination occurs during sampling.
10.2 Measurement uncertainty A new approach to uncertainty assessment within one laboratory using real world samples was introduced in the revised standard. The method is aligned with normative reference EN ISO 20988.
10.3 Determination of the limit of detection (LoD) and
the limit of quantification (LoQ)
The LoD and LoQ concepts replace the former subclause 6.5.4 'Decision limit of the olfactometric measurement'.
11 Measurement records and report Revised text replaces former subclause 9.5 'Presentation and minimum requirements for reporting and archiving results'. The records and reporting requirements for
emission sampling (subclause 11.1) and odour concentration measurement (subclause 11.2) are now in separate subclauses.
Annex D Example of calculations por panel selection The example was modified compared to the former Annex C to reflect the requirement to use n=12 ITE data points as opposed to the n=10 in the former example.
Annex I Example of the calculation of an SROM value for a new defined odorant from an EROM comparison This new informative annex has been added providing an example for the data treatments of the method described in subclause 5.3.2.
Annex J Example of the calculation of measurement uncertainty This new informative annex has been added providing an example for the data treatments of the method described in subclause 10.2.2.
Annex K Dynamic dilution apparatus for sampling This new informative annex was added.
Annex L Considerations for the interpretation of the odour concentration concept for air quality management This new informative annex was added replacing the information provided in the notes of the former subclause 3.3
Annex M Sampling of passive area sources This new informative annex was included to reflect the information obtained in the drafting process. In the end the topic was excluded from the normative scope as it was insufficient to draft a normative approach.
Annex N Significant technical changes This new informative annex contains this table listing the significant technical changes in the revised standard, relative to the first edition, EN13725:2003.


2. Conclusions

   The revision of the first edition of EN 13725:2003 seeks to address the issues where practitioners, but also users of the results of these measurements, felt the method fell short of expectations.

   If the vote of TC264 “Air Quality” is favourable for the revised draft standard delivered by Working Group 2 “Dynamic Olfactometry” the olfactometry practitioners will have a challenge ahead to adapt their practice to a thoroughly revised and improved EN 13725:2021.


3. References

   AS/NZS 4323.3:2001 (R2014) Stationary source emissions Determination of odour concentration by dynamic olfactometry, Standards Australia.

   EN 13725:2003/AC:2006 Air quality - Determination of odour concentration by dynamic olfactometry, CEN, Brussels, Belgium.

   National standard Chile NCh3190:2010, Determinación de la concentración de olor por olfatometría dinámica. Chile.

   National standard Colombia, NTC 5880:2011, Calidad del aire. Determinación de la concentración de olor por olfatomatría dinámica. Colombia.


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