prEN ISO 13164-3

• Abstract:

  ISO 13164-3:2013 specifies a test method for the determination of radon-222 activity concentration in a sample of water following its transfer from the aqueous phase to the air phase by degassing and its detection. It gives recommendations for rapid measurements performed within less than 1 h.; The radon-222 activity concentrations, which can be measured by this test method utilizing currently available instruments, range from 0,1 Bq l−1 to several hundred thousand becquerels per litre for a 100 ml test sample.; This test method is used successfully with drinking water samples. The laboratory is responsible for ensuring the validity of this test method for water samples of untested matrices.; This test method can be applied on field sites or in the laboratory.; Annexes A and B give indications on the necessary counting conditions to meet the required sensitivity for drinking water monitoring

• Status: Not Published
• Publication Date: 07-Nov-2027
• ICS: 13.060.60 - Examination of physical properties of water
• ICS: 17.240 - Radiation measurements
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230 - Water analysis
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 03-Jul-2026
• Completion Date: 03-Jul-2026
• Ref Project: oSIST prEN ISO 13164-3:2026 - Water quality - Radon-222 - Part 3: Test method using emanometry (ISO/DIS 13164-3:2026)

• Revises: EN ISO 13164-3:2020 - Water quality - Radon-222 - Part 3: Test method using emanometry (ISO 13164-3:2013)
• Effective Date: 05-Nov-2024

Overview

prEN ISO 13164-3:2026 is an international standard developed by CEN, specifying a test method for determining the activity concentration of Radon-222 in water using emanometry. This method involves transferring radon from the aqueous to the gas phase by degassing and then detecting it. The standard includes recommendations for rapid measurements-often completed in less than one hour-making it highly effective for timely water quality assessments. It is suitable for measuring a wide range of Radon-222 activity concentrations, from as low as 0.1 Bq/l to several hundred thousand Bq/l for a 100 ml water sample. The method is validated for drinking water but can be applied to various water matrices, either in the laboratory or in the field.

Key Topics

• Measurement Principle: The method is based on degassing water samples to release Radon-222 into an air phase, followed by detection of its alpha radiation using various techniques.
• Sampling and Sample Handling:
  • Clear guidelines for representative sample collection and avoidance of degassing prior to analysis.
  • Specific recommendations for sample volume and container material to prevent radon loss, with PET, glass, and polylactic biopolymer (PLBP) highlighted as suitable options.
  • Emphasis on maintaining water temperature and minimizing storage time due to Radon-222’s short half-life.
• Degassing Techniques: Options for efficient radon transfer include shaking, sparging with radon-free air, or reducing pressure.
• Detection Methods:
  • Scintillation with silver-activated zinc sulfide (ZnS(Ag)), as in Lucas cells, for spot measurements.
  • Air ionization chambers and semiconductor (alpha) detectors are also supported.
• Quality Assurance: Laboratories must follow ISO/IEC 17025 requirements for quality control, instrument verification, and method validation.
• Result Expression and Reporting:
  • Methods for expressing measurement uncertainty, detection limits, and confidence intervals.
  • Comprehensive test reporting in line with international norms.

Applications

• Drinking Water Safety: The method is particularly effective for rapid monitoring of Radon-222 in drinking water, enabling regulatory compliance and public health protection.
• Environmental Monitoring: Useful for groundwater and surface water testing in environmental surveillance programs.
• Regulatory Compliance: Supports adherence to national and international guidelines, such as those specified by the World Health Organization (WHO) and the European Council Directive for radon in water.
• Onsite Analysis: Suitable for both field and laboratory settings, offering flexible deployment scenarios in routine monitoring, emergency response, and operational control of water supplies.
• Wider Water Quality Assessment: Can be applied to various types of water matrices, where laboratory validation confirms matrix-specific suitability.

Related Standards

• ISO 13164-1: Water quality - Radon-222 - Part 1: General principles.
• ISO 5667-1: Water quality - Sampling - Part 1: Guidance on the design of sampling programmes and sampling techniques.
• ISO 5667-3: Water quality - Sampling - Part 3: Preservation and handling of water samples.
• ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories.
• IEC 61577-1 & IEC 61577-2: Instrumentation and requirements for radon measurement in radiation protection contexts.

Practical Value

Implementing prEN ISO 13164-3:2026 ensures accurate, sensitive, and rapid radon-222 measurements in water, addressing public health, safety, and compliance needs. By adhering to international best practices on sampling, detection, and quality control, laboratories and regulatory bodies can trust the reliability of results, support regulatory decisions, and safeguard water quality for consumers and the environment.

Keywords: Radon-222, water quality, emanometry, rapid measurement, drinking water, environmental monitoring, ISO 13164-3, CEN standard, radon testing, water sampling, laboratory quality control.

SLOVENSKI STANDARD
01-junij-2026
Kakovost vode - Radon Rn-222 - 3. del: Preskusna metoda z emanometrijo
(ISO/DIS 13164-3:2026)
Water quality - Radon-222 - Part 3: Test method using emanometry (ISO/DIS 13164-
3:2026)
Wasserbeschaffenheit - Radon-222 - Teil 3: Verfahren mittels Emanometrie (ISO/DIS
13164-3:2026)
Qualité de l'eau - Radon 222 - Partie 3: Méthode d'essai par émanométrie (ISO/DIS
13164-3:2026)
Ta slovenski standard je istoveten z: prEN ISO 13164-3
ICS:
13.060.60 Preiskava fizikalnih lastnosti Examination of physical
vode properties of water
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 13164-3
ISO/TC 147/SC 3
Water quality — Radon-222 —
Secretariat: AFNOR
Part 3:
Voting begins on:
Test method using emanometry 2026-04-10
Voting terminates on:
Qualité de l'eau — Radon 222 —
2026-07-03
Partie 3: Méthode d'essai par émanométrie
ICS: 17.240; 13.060.60; 13.280
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
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STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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POTENTIAL TO BECOME STANDARDS TO
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RECIPIENTS OF THIS DRAFT ARE INVITED
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NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 13164-3:2026(en)
DRAFT
ISO/DIS 13164-3:2026(en)
International
Standard
ISO/DIS 13164-3
ISO/TC 147/SC 3
Water quality — Radon-222 —
Secretariat: AFNOR
Part 3:
Voting begins on:
Test method using emanometry
2026-04-10
Voting terminates on:
Qualité de l'eau — Radon 222 —
2026-07-03
Partie 3: Méthode d'essai par émanométrie
ICS: 17.240; 13.060.60; 13.280
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland Reference number
ISO/DIS 13164-3:2026(en)
ii
ISO/DIS 13164-3:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 3
6 Sampling . 3
6.1 General requirement .3
6.2 Sampling requirement .3
6.3 Sample volume .3
6.4 Container characteristics .3
7 Transportation and storage . 4
8 Transfer of Rn-222 by degassing . 4
8.1 Purpose .4
8.2 Principle .4
9 Detection . 4
9.1 Objective.4
9.2 Principle .4
9.3 Silver-activated zinc sulfide ZnS(Ag) scintillation .4
9.4 Air ionization .5
9.5 Semiconductor (alpha-detection) .5
10 Quality assurance and quality control programme . 5
10.1 General .5
10.2 Influence quantities .5
10.3 Instrument verification .6
10.4 Method verification .6
10.5 Demonstration of analyst capability . .6
11 Expression of results . 6
11.1 Activity concentration .6
11.2 Standard uncertainty of the activity concentration .6
11.3 Decision threshold and limit of detection .7
11.4 Confidence limits .7
12 Calibration . 7
13 Test report . 7
Annex A (informative) Rn-222 Air to Water: Conversion Factor (ω) . 9
Annex B (informative) Examples of measurement methods using scintillation cells .11
Annex C (informative) Example of a measurement method using an ionization chamber . 17
Bibliography .24

iii
ISO/DIS 13164-3:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water Quality, Subcommittee SC 3,
Radioactivity measurements.
This second edition cancels and replaces the first edition (ISO 13164-3:2013), which has been technically
revised.
The main changes are as follows:
— the introduction was updated
— the test report was updated
— a new informative annex was added: Annex A (informative) “Rn-222 Air to Water: Conversion Factor (ω)”
— the bibliography was updated
A list of all parts in the ISO 13164 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 13164-3:2026(en)
Introduction
Radionuclides are present throughout the environment; thus, water bodies (e.g. surface waters, ground
waters, sea waters) contain radionuclides, which can be of either natural or anthropogenic origin:
3 14 40
— naturally occurring radionuclides, including H, C, K and those originating from the thorium and
210 210 222 226 228 227 232 231 234 238
uranium decay series, in particular Pb, Po, Rn, Ra, Ra, Ac, Th, Pa, U, and U
can be found in water bodies due to either natural processes (e.g., desorption from the soil, runoff by rain
water) or released from technological processes involving naturally occurring radioactive materials (e.g.
mining, mineral processing, oil, gas and production, water treatment and the production and the use of
phosphate fertilisers);
3 14 55 59 63 90 99
— anthropogenic radionuclides such as H, C, Fe, Ni, Ni, Sr, Tc, transuranic elements (Np, Pu, Am,
60 137
and Cm) and some gamma emitting radionuclides such as Co and Cs can also be found in natural
waters. Small quantities of anthropogenic radionuclides can be discharged from nuclear facilities to the
environment as a result of authorized routine releases. The radionuclides present in liquid effluents
[1]
are usually controlled before being discharged to the environment and water bodies. Anthropogenic
radionuclides used in medical and industrial applications can be released to the environment after use.
Anthropogenic radionuclides are also found in waters due to the contamination from fallout resulting
above-ground nuclear detonations and accidents such as those that occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentrations in water bodies can vary according to local geological characteristics
and climatic conditions and can be locally and temporally enhanced by releases from nuclear facilities
[2][3]
during planned, existing, and emergency exposure situations. Some drinking water sources can thus
contain radionuclides at activity concentrations that could present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters and to take
proper actions when needed to minimize the health risk.
National regulations usually specify the activity concentration limits that are authorized in drinking waters,
water bodies, and liquid effluents to be discharged to the environment. These limits can vary for planned,
existing, and emergency exposure situations. The WHO does not have a current recommended specific
activity concentration limit for radon in water as radon exposure through indoor air is considered a more
[4]
pressing concern, while in Europe, the implementation of European Council Directive 2013/51/EURATOM,
-1
establishes a radon concentration limit of 100 Bq·l . Compliance with such limits is assessed by measuring
radioactivity in water samples and by comparing the results obtained, with their associated uncertainties,
[5] [6]
as specified by ISO/IEC Guide 98-3 and ISO 5667-20 .
This document contains method to support laboratories which need to determine Rn in water samples.
The method described in this document can be used for various types of waters (see Clause 1). Minor
modifications such as sample volume and counting time can be made if needed to ensure that the
characteristic limit, decision threshold, detection limit, and uncertainties are below the required limits.
This can be done for several reasons such as emergency situations, lower national guidance limits, and
operational requirements.
v
DRAFT International Standard ISO/DIS 13164-3:2026(en)
Water quality — Radon-222 —
Part 3:
Test method using emanometry
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices and to determine
the applicability of any other restrictions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be
carried out by suitably qualified staff.
1 Scope
This part of ISO 13164 specifies a test method for the determination of Rn activity concentration
in a sample of water following its transfer from the aqueous phase to the gas phase by degassing and its
detection. It gives recommendations for rapid measurements performed within less than 1 h.
The Rn activity concentrations, which can be measured by this test method utilizing currently available
−1
instruments, range from 0,1 Bq∙l to several hundred thousand becquerels per litre for a 100 ml test sample.
This test method is used successfully with drinking water samples. The laboratory is responsible for
ensuring the validity of this test method for water samples of untested matrices.
This test method can be applied on field sites or in the laboratory.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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.
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and sampling
techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 11929 (all parts), Determination of the characteristic limits (decision threshold, detection limit and limits of
the confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 13164-1, Water quality — Radon-222 — Part 1: General principles
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
IEC 61577-1, Radiation protection instrumentation — Radon and radon decay product measuring
instruments — Part 1: General principles
IEC 61577-2, Radiation protection instrumentation — Radon and radon decay product measuring
instruments — Part 2: Specific requirements for radon measuring instruments

ISO/DIS 13164-3:2026(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000-10 and ISO 13164-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
For the purposes of this document, the symbols defined in ISO 80000-10. ISO 13164-1, and the following
apply.
222 −3
c measured Rn activity concentration in the air of the measuring Bq·m
system after degassing
222 −3
c Rn activity concentration in the air of the measuring system before Bq·m
degassing
222 −1
c activity concentration of Rn in water Bq·l
A
−1
*
Bq·l
decision threshold
c
A
−1
#
Bq·l
detection limit
c
A
−1
 
Bq·l
lower and upper limits of the confidence interval
c , c
A A
f conversion factor from cubic metre to litre: 0,001
c
f correction factor for the decay of Rn during time interval t, dimensionless
d
k , k quantiles of the standardized normal distribution for the probabilities, p and
p q
q, respectively
L Ostwald coefficient
water temperature °C
T
HO
t time interval between the sampling and the measurement s
U expanded uncertainty calculated by U = k·u(c ) with k = 2
A
u(c ) standard uncertainty associated with the measurement result
A
volume of test sample m
V
HO
volume of air in the measurement system m
V
a
α, β probability of the error of the first and second kind, respectively
γ probability for the confidence interval of the activity concentration
222 −1
λ decay constant of Rn, in reciprocal second s
Φ distribution function of the standardized normal distribution

ISO/DIS 13164-3:2026(en)
5 Principle
The determination of Rn activity concentration in water by degassing into the gas phase is based on the:
— collection of a representative sample of the water at time t in a suitable container;
— transfer of Rn dissolved in the water to the gas phase by degassing;
— detection of the alpha-radiation emitted by the Rn or its short-lived decay products present in the gas
phase.
The Rn activity concentration in the water is determined from the activity concentration in the gas phase,
taking account of the Ostwald coefficient (see ISO 13164-1).
6 Sampling
6.1 General requirement
The sample shall be representative of the environment to be analysed at a given time.
6.2 Sampling requirement
The sampling shall be carried out in compliance with the conditions and techniques specified in ISO 5667-1,
ISO 5667-3, and ISO 13164-1. The temperature of the water shall be measured and recorded during the
sampling process.
Fill the container completely and fit the cap in such a way as to avoid the presence of air above the sample.
The container shall be filled in such a way as to avoid degassing the Rn in the water sample. The sampling
techniques to be used vary according to the actual situation.
When the analytical laboratory is not in charge of sampling, the laboratory shall supply the container for the
measurement and specify the sampling procedure to the person carrying out the sampling operation.
It is recommended that several discrete samples be taken in case of problems arising in relation to the
sampling conditions or transportation of the samples.
6.3 Sample volume
A sample of 1 l is recommended, because this quantity is applicable to any type of equipment.
6.4 Container characteristics
The choice and preparation of a suitable container are important (see ISO 5667-3).
The container and cap used to contain the sample shall comply with the following requirements.
— They shall be made from inert materials, impermeable to Rn, non-hydrophobic (in order not to adsorb
Rn and its decay products from the surrounding atmosphere).
The volume of the container should be compatible with the water volume required by the degassing
technique used.
Polyethylene terephthalate (PET), polylactic biopolymer (PLBP) and glass are suitable as the container
[10]
material .
ISO/DIS 13164-3:2026(en)
7 Transportation and storage
During transportation and storage, the sample shall be maintained at a temperature below that of the
original water (but above 0 °C) until it is ready for analysis. The container shall be protected and tightly
sealed. The container shall be packed in an appropriate manner in order to prevent any leakage.
The period of transportation and storage prior to analysis shall be as short as possible given the half-life of
Rn, the expected activity concentration, and the detection limit of the measurement method to be used.
On arrival at the laboratory, the sample shall be maintained at a temperature below that of the original water
(but above 0 °C), if it cannot be analysed immediately. The sample shall be analysed as soon as possible.
Experience indicates that it is essential that the time between sampling and analysis not exceed 48 h.
8 Transfer of Rn-222 by degassing
8.1 Purpose
This technique is used to transfer the Rn dissolved in the water into the gas phase so that it can be
detected and measured in its gaseous state.
8.2 Principle
222 222
As the Ostwald coefficient of Rn in water is fairly low, the dissolved Rn degasses naturally into the air
with relatively slow kinetics (over a few hours) (see ISO 13164-1).
In order to accelerate the degassing process, several means can be used:
— shaking the sample;
— sparging Rn-free air through the water sample using a fine air bubble to increase the gas exchange
surface;
— decreasing the pressure in the gas phase.
In order to improve the detection limit of the measurement method, it is necessary for the Rn activity
concentration in the gas used for the degassing process to be as low as possible and to be measured before
degassing the Rn from the water.
9 Detection
9.1 Objective
The purpose of the detector is to quantify the alpha-particles emitted by the Rn and/or its short-lived
decay products that is directly related to the activity concentration of the Rn in the gas phase.
9.2 Principle
[7
A number of detection techniques can be used (see ISO 11665-1 ).
9.3 Silver-activated zinc sulfide ZnS(Ag) scintillation
Some electrons in scintillating media, such as ZnS(Ag), have the particular feature of emitting photons by
returning to their ground state when they are excited by an alpha-particle. These emitted photons can be
detected using a photomultiplier or equivalent.
This is the principle adopted for scintillation cells (such as Lucas cells) used for Rn spot measurement
[9]
(see References [11]–[12] and ISO 11665-6 ).

ISO/DIS 13164-3:2026(en)
9.4 Air ionization
When it travels through the air, each alpha-particle creates several tens of thousands of ion pairs which,
under some experimental conditions, produce an ionization current. Although very low, this current can be
measured using an ionization chamber that gives the activity concentration of Rn and its decay products.
When the sampling is performed through a filtering medium, only Rn diffuses into the ionization
chamber and the signal is proportional to the Rn activity concentration (see References [13]–[15] and
[8]
ISO 11665-5 ).
9.5 Semiconductor (alpha-detection)
A semiconductor detector, e.g. made of silicon, converts the energy from an incident alpha-particle into
electric charges. These are converted into pulses with an amplitude proportional to the energy of the alpha-
particles emitted by the Rn and its short-lived decay products (see References [16]–[18]).
NOTE This detection principle is occasionally associated with electrostatic precipitation of the alpha-emitter
isotopes.
10 Quality assurance and quality control programme
10.1 General
Quality control operations shall meet the requirements of ISO/IEC 17025.
10.2 Influence quantities
Various quantities can lead to measurement bias that could induce non-representative results. In the specific
case of the emanometric method, influence quantities can affect the following stages in the measurement
process: sampling; transportation and storage of the sample; transfer of Rn from the aqueous phase to
another; and the measurement of the Rn activity concentration.
During the sampling, consider particularly the:
— water temperature;
— turbulence in the water;
— volume of air in the container.
During the transfer of the Rn from the water to the gas phase by degassing, the influence of the water
temperature shall be taken into account.
During measurement, consider particularly the:
— detector storage conditions prior to beginning the measurement;
— stability of the characteristics of the detection system (contamination of the detection surface, saturation,
etc.);
— possible presence of other alpha-emitters (radon isotopes) in the detection volume.
When the delay between the
...