🌿 Determination of the odour concentration of gas samples by dynamic olfactometry with a panel of assessors (the sample is diluted with neutral gas down to the detection threshold; 1 ouE/m3 at the threshold, range usually 10^1–10^7 ouE/m3) and of the odour emission rate from point sources and active area sources (e.g. biofilters) — unit referenced to n-butanol: 1 EROM = 123 µg; sampling also of humid gases and at temperatures up to 200 °C; excluding the odour emission rate from volume sources and passive area sources, PN-EN 13725

Environment PN-EN 13725

Overview

WHAT THE STANDARD COVERS. The scope on the PKN catalogue card of PN-EN 13725:2022-07 (English version) begins (our translation): “This document specifies an objective method for the determination of the odour concentration of a gaseous sample using dynamic olfactometry with human assessors. This document also specifies a method for the determination of the emission rate of odours from stationary sources, in particular: a) point sources…”; the card then reproduces Clause 1 of the standard (described below). We read the text of the standard in the iTeh sample of SIST EN 13725:2022 (text of EN 13725:2022, English): from the title page through the contents, the European foreword and Clauses 1–2 to the definitions in 3.1 and 3.2 (up to and including 3.2.5). Outside the sample remain the further definitions (3.2.6 onwards, 3.3), Clauses 4 (symbols), 5 (principle — gas sampling and determination of the concentration), 6 (apparatus, neutral gas, olfactometer, room, panel), 7 (quality requirements — accuracy model, sensory requirements, requirements for the dilution apparatus), 8 (measurement objective and plan), 9 (sampling from point and area sources, olfactometric analysis, safety, calculations), 10 (field blank, uncertainty, limit of detection and quantification), 11 (test report) and the informative Annexes A–N (among others physiological principles, calculation examples, panel selection, dilution during sampling, passive area sources, technical changes compared with the 2003 edition).

ACCORDING TO THE TEXT OF EN 13725:2022 (foreword, Clauses 1–2, 3.1–3.2.5). The standard was prepared by CEN/TC 264 “Air quality” (secretariat DIN); CEN approved it on 12 December 2021, and a corrected version was issued on 6 April 2022; it replaced EN 13725:2003 — the methods of the first edition and their quality criteria were validated in numerous proficiency tests; the main changes are listed in Annex N; all Annexes A–N are informative. Scope (1): an objective method for determining the odour concentration of a gaseous sample by dynamic olfactometry with assessors and a method for determining the odour emission rate from stationary sources: a) point sources (ducted emissions), b) active area sources (e.g. biofilters); for emissions from stationary sources other European standards also apply, in particular EN 15259 and EN ISO 16911-1, especially when the measurements serve the directives on industrial emissions; the analysis step alone (the odour concentration of a sample, whatever its origin) may also be used outside industrial emissions (e.g. the mass concentration of odorants at the detection threshold, the efficiency of indoor air deodorisation) — the requirements on planning and sampling may then be omitted or adapted. Subject: odorous gases, mixtures of odorants of known and unknown composition in air or nitrogen; the sensor is the panel of assessors; unit — European odour unit per cubic metre (ouE/m3); the concentration is determined from the dilution factor needed to reach the detection threshold, at which it is by definition 1 ouE/m3; range usually from 10^1 to 10^7 ouE/m3 (with predilution). Applications: mass concentration of odorants at the threshold (g/m3), SROM value of a secondary reference gas (mol), concentration of mixtures (ouE/m3), odour emission rate from point sources and active area sources with predilution during sampling, sampling of gases with high humidity and temperature (up to 200 °C), efficiency of odour abatement techniques; the odour emission rate requires a gas velocity measurement for the volume flow rate. Outside the scope: odours from solid particles or droplets suspended in the emission; the strategy for variable emissions; subjective methods for perceived intensity above the threshold, hedonic tone (pleasantness) and annoyance; direct measurement of exposure in ambient air (field methods according to EN 16841-1); direct olfactometry, including field olfactometry; static olfactometry; the recognition (identification) threshold of an odour; the odour emission rate from volume sources (e.g. fugitive emissions from buildings) and from passive area sources; the relationship between emission, dispersion, exposure and annoyance — very complex, dependent on the atmosphere, hedonic tone and characteristics of the receptors, varying between people and over time. Normative references (2): EN 15259:2007, EN ISO 16911-1, EN ISO 20988:2007 (estimation of uncertainty). Definitions (3.1, 3.2): among others the detection threshold of a sample — the dilution factor at which the odour is detected with a probability of 0.5; dynamic dilution — mixing of two known gas flows; European odour unit — the amount of odorants which, evaporated into 1 m3 of neutral gas under standard conditions, causes a physiological response from a panel equivalent to 1 EROM; EROM — an agreed value: primary odorant n-butanol (CAS 71-36-3), 1 EROM = 123 µg of n-butanol, in 1 m3 of neutral gas a concentration of 0.040 µmol/mol; SROM — the mass of another odorant giving a stimulus equivalent to the EROM; neutral gas — air or nitrogen as odourless as possible, not interfering with the panel; delayed olfactometry (with storage of the sample) and direct olfactometry (without delay); the measuring range of the olfactometer — from the smallest dilution factor multiplied by the step factor to the power 1.5 to the largest divided by the step factor to the power 1.5; odour abatement efficiency — the reduction of the odour emission rate (with the note that a decrease in concentration does not mean a proportional decrease in perceived intensity); yes/no method; active area source — with defined dimensions and a defined volume flow rate; field blank — a check that no significant contamination occurred at any stage (preparation, transport, installation, analysis).

STATUS (cards as of 03.10.2026). The PKN card of PN-EN 13725:2022-07 (English version, published 20-07-2022, 126 pages, price group XB) has no “Withdrawn” header: Health, Environment and Medicine Sector, KT 280 Air Quality, ICS 13.040.99, “Introduces: EN 13725:2022 [IDT]”, “Replaces: PN-EN 13725:2007 — Polish version”. The card of PN-EN 13725:2007 (Polish version, “Air quality — Determination of odour concentration by dynamic olfactometry”, published 02-07-2007, 73 pages) has the header “Withdrawn”: withdrawal date 20-07-2022, “Replaced by: PN-EN 13725:2022-07 — English version”; it introduced EN 13725:2003 and the corrigendum AC:2006. The 2022 edition is available in the PKN catalogue only in English (search, term “PN-EN 13725”, 03.10.2026). In the iTeh catalogue (read on 03.10.2026) EN 13725:2022 has the status “Published”, CEN/TC 264/WG 2 “Odours”. What changed for the result between the 2003 and 2022 editions is listed in Annex N, which we did not read; a comparison of titles and scopes shows that the 2022 edition explicitly covers the odour emission rate from stationary sources (“and odour emission rate”), whereas the old one did not have this in its title. The measurement of velocity and volume flow rate on which the odour emission rate is based is described in a separate entry “Velocity and volumetric flow rate of gases in ducts — Pitot tube (manual reference method)” (PN-EN ISO 16911-1).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 03.10.2026). The number 13725 appears in 12 records at 4 laboratories: AB 116, AB 833, AB 1426, AB 1824. In the current PCA documents (read on 03.10.2026, issues from 21.03.2025 to 30.07.2026) the number appears in 11 rows of the same 4 laboratories (AB 1824 — 5, AB 833 — 3, AB 1426 — 2, AB 116 — 1; at AB 833 two sampling items share one cell with the standard). The form “PN-EN 13725:2022-07” at three laboratories, for sampling at AB 833 and AB 1824 “excluding clause 9.1.4.3”; AB 116 cites the withdrawn PN-EN 13725:2007 — in a PCA document issued on 12.03.2026, almost four years after that edition was withdrawn. AB 833 and AB 1426 also cite the guideline VDI 3880:2011, AB 1824 for sampling from rooms — its own instruction IR-01-03. The “Laboratories” tab (“PN-EN 13725”) shows the same 4 laboratories — checked with the tab query on the production server labcoda.pl on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Only two laboratories have the odour concentration itself by dynamic olfactometry in their scope: AB 1426 — (12–13 000 000) ouE/m3, with the calculated odour emission rate and deodorisation efficiency, and AB 116 — “odour concentration” in the workplace and in the general environment, (15–46000) OUE/m3, according to the 2007 edition. AB 833 and AB 1824 have sampling by the “lung method” from point sources and active area sources and the odour emission rate and deodorisation efficiency by calculation — without an item for the determination of the odour concentration itself in their scope. Clause 1 of the standard (items ix and x) excludes the determination of the odour emission rate from volume sources and passive area sources — not sampling itself, to which, for passive sources, an informative annex is devoted (outside the sample). Sampling from volume sources is held by AB 1426 (with PN-EN 13725 and VDI 3880) and AB 1824 (from rooms, with PN-EN 13725 and instruction IR-01-03), and from passive area sources by AB 1426 and AB 1824, which here cite only VDI 3880. The upper limit of 13 000 000 ouE/m3 at AB 1426 exceeds the typical range from Clause 1 (up to 10^7 ouE/m3), which the standard gives as “usually”, not as a limit.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the unit: 1 ouE/m3 is by definition the detection threshold of the panel, referenced to n-butanol (1 EROM = 123 µg) — an “odour unit” without reference to the EROM (definition 3.1.33) is not the same quantity, so results from laboratories working with another reference are not comparable. With the edition: a result according to PN-EN 13725:2007 and one according to the 2022 edition come from different versions of the requirements (changes — Annex N) — the report must state the edition. With efficiency: a decrease in odour concentration after an abatement installation does not mean a proportional decrease in perceived intensity (3.1.29, note). With the emission rate: the odour emission rate requires the volume flow rate of the gas from a velocity measurement (1) — an error in velocity is carried directly into the odour emission rate. With sources: an odour emission rate from a volume source or a passive area source has no basis in this standard (1, ix–x) — the standard measures the odour concentration of a sample taken from it, but does not describe the conversion to an emission rate. With interpretation: odour concentration and odour emission rate say nothing about annoyance — the standard explicitly excludes its relationship to emission (1).

WHAT WE DO NOT GIVE. We did not read Clauses 4–11 and the annexes, so we do not give the number of assessors and the criteria for their selection, the quality criteria (accuracy, repeatability), the requirements for the olfactometer and the room, the storage time of samples, bag materials, the calculation method, the uncertainty or the content of clause 9.1.4.3 excluded by two laboratories. Nor do we give the content of the guideline VDI 3880 or the requirements of regulations on odours.

Method principle

The gas sample taken (with predilution during sampling if necessary) is mixed in a dynamic olfactometer in known ratios with neutral gas and presented to the assessors in series of dilutions; each assessor judges whether they perceive an odour. From the panel's responses, the dilution factor at which the odour is detected with a probability of 0.5 is determined — this is the odour concentration in ouE/m3, referenced to n-butanol by calibration of the panel (1 EROM = 123 µg). The odour emission rate from a point source or an active area source is the product of the odour concentration and the volume flow rate of the gas.

Applications

• Odorous gases, mixtures of odorants of known and unknown composition in air or nitrogen — odour concentration, usually 10^1–10^7 ouE/m3 (1)
• Odour emission rate from point sources and active area sources (e.g. biofilters); sampling up to 200 °C and at high humidity; efficiency of odour abatement techniques (1)
• Outside the scope: odour emission rate from volume sources and passive area sources, field and static olfactometry, intensity, hedonic tone, annoyance (1)
• General environment, gases emitted to air, rooms, workplace — sampling, concentration, odour emission rate and deodorisation efficiency in the accreditation scopes of 4 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 13725:2022-07

Title (PL)

Emisja ze źródeł stacjonarnych — Oznaczanie stężenia odorów za pomocą olfaktometrii dynamicznej i szybkości emisji odorów

Title (EN)

Stationary source emissions — Determination of odour concentration by dynamic olfactometry and odour emission rate

Step-by-step procedure

1. Measurement objective and plan

   According to EN 15259; for the odour emission rate — measurement of velocity and volume flow rate according to EN ISO 16911-1. PN-EN 13725:2022-07 current (PKN card as of 03.10.2026).

2. Sampling

   From a point source or an active area source, with predilution if necessary; we do not give the details (Clause 9).

3. Olfactometric analysis

   Series of dynamic dilutions presented to the panel of assessors; the panel is selected and checked against n-butanol — we do not give the criteria (Clauses 6–7).

4. Result

   Odour concentration in ouE/m3 as the dilution factor at the detection threshold of the panel; odour emission rate — concentration times volume flow rate.

5. Report

   With the edition of the standard and any exclusions; without conclusions about annoyance, which the standard does not cover.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sampling on stacks and biofilters — work at height, hot and humid gases (up to 200 °C); the safety of samplers, assessors and operators is described in 9.5 outside the sample
• Assessors sniff diluted emission samples — we do not give the requirements of 9.5 for their protection (outside the sample)
• n-Butanol — flammable, irritant

Frequently asked questions