SIST EN ISO 11665-3:2015

Measurement of radioactivity in the environment - Air: radon-222 - Part 3: Spot measurement method of the potential alpha energy concentration of its short-lived decay products (ISO 11665-3:2012)

ISO 11665-3:2012 describes spot measurement methods for determining the activity concentration of short-lived radon-222 decay products in the air and for calculating the potential alpha energy concentration.
ISO 11665-3:2012 gives indications for performing a spot measurement of the potential alpha energy concentration, after sampling at a given place for several minutes, and the conditions of use for the measuring devices.

Ermittlung der Radioaktivität in der Umwelt - Luft: Radon-222 - Teil 3: Punktmessverfahren der potenziellen Alpha-Energiekonzentration der kurzlebigen Radon-Folgeprodukte (ISO 11665-3:2012)

Mesurage de la radioactivité dans l'environnement - Air: radon 222 - Partie 3: Méthode de mesure ponctuelle de l'énergie alpha potentielle volumique de ses descendants à vie courte (ISO 11665-3:2012)

L'ISO 11665-3:2012 décrit les méthodes de mesure ponctuelle destinées à déterminer l'activité volumique des descendants à vie courte du radon 222 dans l'air et à calculer de l'énergie alpha potentielle volumique.
L'ISO 11665-3:2012 fournit des indications pour réaliser un mesurage ponctuel de l'énergie alpha potentielle volumique avec un prélèvement effectué en un lieu donné pendant plusieurs minutes, et sur les conditions d'utilisation des dispositifs de mesure.

Merjenje radioaktivnosti v okolju - Zrak: radon-222 - 3. del: Točkovna metoda za merjenje potencialne koncentracije alfa energije njegovih kratkoživih razpadnih produktov (ISO 11665-3:2012)

ISO 11665-3:2012 opisuje metode točkovnega merjenja za določanje koncentracije aktivnosti kratkoživih razpadnih produktov radona-222 v zraku in izračun potencialne koncentracije alfa energije. ISO 11665-3:2012 podaja navedbe za izvajanje točkovnega merjenja potencialne koncentracije alfa energije po večminutnem vzorčenju na danem mestu in pogoje uporabe za merilne naprave.

General Information

• Status: Withdrawn
• Public Enquiry End Date: 30-Mar-2015
• Publication Date: 18-Oct-2015
• Withdrawal Date: 12-Feb-2020
• ICS: 13.040.99 - Other standards related to air quality
• ICS: 17.240 - Radiation measurements
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 13-Feb-2020
• Due Date: 07-Mar-2020
• Completion Date: 13-Feb-2020
• Ref Project: EN ISO 11665-3:2015 - Measurement of radioactivity in the environment - Air: radon-222 - Part 3: Spot measurement method of the potential alpha energy concentration of its short-lived decay products (ISO 11665-3:2012)

Relations

• Replaced By: SIST EN ISO 11665-3:2020 - Measurement of radioactivity in the environment - Air: radon-222 - Part 3: Spot measurement method of the potential alpha energy concentration of its short-lived decay products (ISO 11665-3:2020)
• Effective Date: 12-Feb-2020
• Revised: SIST EN ISO 11665-3:2020 - Measurement of radioactivity in the environment - Air: radon-222 - Part 3: Spot measurement method of the potential alpha energy concentration of its short-lived decay products (ISO 11665-3:2020)
• Effective Date: 13-Jun-2018

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 11665-3:2015
01-november-2015
0HUMHQMHUDGLRDNWLYQRVWLYRNROMX=UDNUDGRQGHO7RþNRYQDPHWRGD]D
PHUMHQMHSRWHQFLDOQHNRQFHQWUDFLMHDOIDHQHUJLMHQMHJRYLKNUDWNRåLYLKUD]SDGQLK
SURGXNWRY,62
Measurement of radioactivity in the environment - Air: radon-222 - Part 3: Spot
measurement method of the potential alpha energy concentration of its short-lived decay
products (ISO 11665-3:2012)
Ermittlung der Radioaktivität in der Umwelt - Luft: Radon-222 - Teil 3:
Punktmessverfahren der potenziellen Alpha-Energiekonzentration der kurzlebigen
Radon-Folgeprodukte (ISO 11665-3:2012)
Mesurage de la radioactivité dans l'environnement - Air: radon 222 - Partie 3: Méthode
de mesure ponctuelle de l'énergie alpha potentielle volumique de ses descendants à vie
courte (ISO 11665-3:2012)
Ta slovenski standard je istoveten z: EN ISO 11665-3:2015
ICS:
13.040.99 Drugi standardi v zvezi s Other standards related to air
kakovostjo zraka quality
17.240 Merjenje sevanja Radiation measurements
SIST EN ISO 11665-3:2015 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN ISO 11665-3:2015

---------------------- Page: 2 ----------------------

SIST EN ISO 11665-3:2015


EN ISO 11665-3
EUROPEAN STANDARD

NORME EUROPÉENNE

September 2015
EUROPÄISCHE NORM
ICS 17.240
English Version

Measurement of radioactivity in the environment - Air:
radon-222 - Part 3: Spot measurement method of the
potential alpha energy concentration of its short-lived
decay products (ISO 11665-3:2012)
Mesurage de la radioactivité dans l'environnement - Ermittlung der Radioaktivität in der Umwelt - Luft:
Air: radon 222 - Partie 3: Méthode de mesure Radon-222 - Teil 3: Punktmessverfahren der
ponctuelle de l'énergie alpha potentielle volumique de potenziellen Alpha-Energiekonzentration der
ses descendants à vie courte (ISO 11665-3:2012) kurzlebigen Radon-Folgeprodukte (ISO 11665-3:2012)
This European Standard was approved by CEN on 12 June 2015.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11665-3:2015 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST EN ISO 11665-3:2015
EN ISO 11665-3:2015 (E)
Contents Page
European foreword . 3

2

---------------------- Page: 4 ----------------------

SIST EN ISO 11665-3:2015
EN ISO 11665-3:2015 (E)
European foreword
The text of ISO 11665-3:2012 has been prepared by Technical Committee ISO/TC 85 “Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 11665-3:2015 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
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 2016, and conflicting national standards shall
be withdrawn at the latest by March 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 11665-3:2012 has been approved by CEN as EN ISO 11665-3:2015 without any
modification.
3

---------------------- Page: 5 ----------------------

SIST EN ISO 11665-3:2015

---------------------- Page: 6 ----------------------

SIST EN ISO 11665-3:2015
INTERNATIONAL ISO
STANDARD 11665-3
First edition
2012-07-15
Measurement of radioactivity in the
environment — Air: radon-222 —
Part 3:
Spot measurement method of the
potential alpha energy concentration of
its short-lived decay products
Mesurage de la radioactivité dans l’environnement — Air: radon 222 —
Partie 3: Méthode de mesure ponctuelle de l’énergie alpha potentielle
volumique de ses descendants à vie courte
Reference number
ISO 11665-3:2012(E)
©
ISO 2012

---------------------- Page: 7 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

---------------------- Page: 8 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 2
4 Principle of the measurement method . 3
5 Equipment . 3
6 Sampling . 4
6.1 General . 4
6.2 Sampling objective . 4
6.3 Sampling characteristics . 4
6.4 Sampling conditions . 5
7 Detection method . 5
8 Measurement . 5
8.1 Procedure . 5
8.2 Influence quantities . 6
8.3 Calibration . 6
9 Expression of results . 7
9.1 General . 7
9.2 Potential alpha energy concentration . 7
9.3 Standard uncertainty . 7
9.4 Decision threshold . 8
9.5 Detection limit . 8
9.6 Limits of the confidence interval . 9
10 Test report . 9
Annex A (informative) Examples of gross alpha counting protocols . 11
Annex B (informative) Calculation of the coefficients k , k and k .12
218 ,j 214 ,j 214 ,j
Po Pb Bi
Annex C (informative) Measurement method using gross alpha counting according to the
Thomas protocol .16
Bibliography .19
© ISO 2012 – All rights reserved iii

---------------------- Page: 9 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 11665-3 was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies, and
radiological protection, Subcommittee SC 2, Radiological protection.
ISO 11665 consists of the following parts, under the general title Measurement of radioactivity in the
environment — Air: radon-222:
— Part 1: Origins of radon and its short-lived decay products and associated measurement methods
— Part 2: Integrated measurement method for determining average potential alpha energy concentration of
its short-lived decay products
— Part 3: Spot measurement method of the potential alpha energy concentration of its short-lived decay products
— Part 4: Integrated measurement method for determining average activity concentration using passive
sampling and delayed analysis
— Part 5: Continuous measurement method of the activity concentration
— Part 6: Spot measurement method of the activity concentration
— Part 7: Accumulation method for estimating surface exhalation rate
— Part 8: Methodologies for initial and additional investigations in buildings
The following parts are under preparation:
— Part 9: Method for determining exhalation rate of dense building materials
— Part 10: Determination of diffusion coefficient in waterproof materials using activity concentration measurement
iv © ISO 2012 – All rights reserved

---------------------- Page: 10 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
Introduction
Radon isotopes 222, 220 and 219 are radioactive gases produced by the disintegration of radium isotopes 226,
224 and 223, which are decay products of uranium-238, thorium-232 and uranium-235 respectively, and are
all found in the earth’s crust. Solid elements, also radioactive, followed by stable lead are produced by radon
[1]
disintegration .
When disintegrating, radon emits alpha particles and generates solid decay products, which are also radioactive
(polonium, bismuth, lead, etc.). The potential effects on human health of radon lie in its solid decay products
rather than the gas itself. Whether or not they are attached to atmospheric aerosols, radon decay products can
be inhaled and deposited in the bronchopulmonary tree to varying depths according to their size.
Radon is today considered to be the main source of human exposure to natural radiation. The UNSCEAR
[2]
(2006) report suggests that, at the worldwide level, radon accounts for around 52 % of global average
exposure to natural radiation. The radiological impact of isotope 222 (48 %) is far more significant than isotope
220 (4 %), while isotope 219 is considered negligible. For this reason, references to radon in this part of
ISO 11665 refer only to radon-222.
Radon activity concentration can vary by one to multiple orders of magnitude over time and space. Exposure
to radon and its decay products varies tremendously from one area to another, as it depends firstly on the
amount of radon emitted by the soil and the building materials in each area and, secondly, on the degree of
containment and weather conditions in the areas where individuals are exposed.
Variations of a few nanojoules per cubic metre to several thousand nanojoules per cubic metre are observed
in the potential alpha energy concentration of short-lived radon decay products.
The potential alpha energy concentration of short-lived radon-222 decay products in the atmosphere can
be measured by spot and integrated measurement methods (see ISO 11665-1 and ISO 11665-2). This part
of ISO 11665 deals with spot measurement methods. A spot measurement of the potential alpha energy
concentration relates to the time when the measurement is taken and has no significance in annual exposure.
This type of measurement does not therefore apply when assessing the annual exposure.
NOTE The origin of radon-222 and its short-lived decay products in the atmospheric environment and other
measurement methods are described generally in ISO 11665-1.
© ISO 2012 – All rights reserved v

---------------------- Page: 11 ----------------------

SIST EN ISO 11665-3:2015

---------------------- Page: 12 ----------------------

SIST EN ISO 11665-3:2015
INTERNATIONAL STANDARD ISO 11665-3:2012(E)
Measurement of radioactivity in the environment — Air:
radon-222 —
Part 3:
Spot measurement method of the potential alpha energy
concentration of its short-lived decay products
1 Scope
This part of ISO 11665 describes spot measurement methods for determining the activity concentration of
short-lived radon-222 decay products in the air and for calculating the potential alpha energy concentration.
This part of ISO 11665 gives indications for performing a spot measurement of the potential alpha energy concentration,
after sampling at a given place for several minutes, and the conditions of use for the measuring devices.
This measurement method is applicable for a rapid assessment of the potential alpha energy concentration.
The result obtained cannot be extrapolated to an annual estimate potential alpha energy concentration of
short-lived radon-222 decay products. Thus, this type of measurement is not applicable for the assessment of
annual exposure.
This measurement method is applicable to air samples with potential alpha energy concentration greater
3
than 5 nJ/m .
NOTE This part of ISO 11665 does not address the potential contribution of radon-220 decay products.
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.
ISO 11665-1, Measurement of radioactivity in the environment — Air: radon-222 — Part 1: Origins of radon and
its short-lived decay products and associated measurement methods
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
IEC 61577-1, Radiation protection instrumentation — Radon and radon decay product measuring instruments —
Part 1: General principles
IEC 61577-3, Radiation protection instrumentation — Radon and radon decay product measuring instruments —
Part 3: Specific requirements for radon decay product measuring instruments
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11665-1 apply.
© ISO 2012 – All rights reserved 1

---------------------- Page: 13 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
3.2 Symbols
For the purposes of this document, the symbols given in ISO 11665-1 and the following apply.
C
activity concentration of the nuclide i, in becquerels per cubic metre
i
E alpha particle energy produced by the disintegration of the nuclide i, in joules
AE,i
E total alpha particle energy potentially produced by the nuclide i, in joules
AEt,i
E potential alpha energy of the nuclide i, in joules
PAE,i
potential alpha energy concentration of the nuclide i, in joules per cubic metre
E
PAEC,i
*
decision threshold of the potential alpha energy concentration of the nuclide i, in joules
E
PAEC,i
per cubic metre
#
detection limit of the of the potential alpha energy concentration of the nuclide i, in joules
E
PAEC,i
per cubic metre

lower limit of the confidence interval of the potential alpha energy concentration of the
E
PAEC,i
nuclide i, in joules per cubic metre

upper limit of the confidence interval of the potential alpha energy concentration of the
E
PAEC,i
nuclide i, in joules per cubic metre
th
I
j number of gross counts obtained between times t and t
j j cj
th
I j number of background counts obtained between times t and t
0,j j cj
th
k coefficient related to the j number of gross count for radon decay product i, depending on
i,j
the decay constants of the radon decay products, the sampling duration, t , and the times
s
t and t , per square second
j cj
N
number of atoms of the nuclide i
i
n
counting number depending on the gross alpha counting protocol used
Q
sampling flow-rate, in cubic metres per second
t end time of counting j, in seconds
cj
t start time of counting j, in seconds
j
t sampling duration, in seconds
s
U expanded uncertainty calculated by U = k⋅u( ) with k = 2
u( ) standard uncertainty associated with the measurement result
u ( ) relative standard uncertainty
rel
V sampled volume, in cubic metres
ε counting efficiency, in pulses per disintegration
c
λ decay constant of the nuclide i, per second
i
2 © ISO 2012 – All rights reserved

---------------------- Page: 14 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
4 Principle of the measurement method
Spot measurement of the potential alpha energy concentration of short-lived radon-222 decay products is
based on the following elements:
a) grab sampling, at time t, of short-lived radon decay products contained in a volume of air representative of
the atmosphere under investigation, using a high-efficiency filtering membrane;
b) repeated gross alpha measurements of the collected decay products using a detector sensitive to alpha
particles; the counting stage starts after sampling has stopped;
c) calculation of the activity concentrations of the radon decay products using the laws of radioactive decay
and the counting results from a preset duration, repeated at given times.
The gross alpha measurement method quantifies alpha particles emitted by short-lived radon decay products.
222 218
The Rn decay product chain shows that 99,98 % of the decays of Po result in the emission of alpha
214 214
particles. It can, therefore, be considered as a pure alpha emitter. Pb and Bi are not alpha emitters, but
214
they contribute to the appearance of alpha particles from the decay of Po.
After collecting the air sample, the gross alpha activity is measured for various counting durations. Because of
the fast decay of radon decay products, the isotopic composition of a sample rapidly changes during collection
as well as during the counting durations. Repeated measurements of the gross alpha activity are necessary
in order to describe the decay of the sample and thereby calculate the amounts of the various decay products
which were originally collected in the air sample.
222
NOTE Although Rn and its decay products are usually found in higher quantity, environmental air samples can
220
also contain significant activity of radonuclides of the Rn decay chain as well as other airborne long-lived radionuclides.
In such cases, the formulas and procedures given in this part of ISO 11665 need to be adapted to take into account these
additional radionuclides.
5 Equipment
The apparatus shall include a sampling system and a detection system composed of a detector connected to a
counting system (see Figure 1). The measuring devices used shall comply with IEC 61577-1 and IEC 61577-3.
The sampling system shall include the following components:
a) an open filter holder allowing fast and easy removal of the filter after sampling;
b) a pump;
c) a high-efficiency particulate air filter (HEPA filter with a minimum efficiency of 99,97 % for a particle
size of 0,3 µm);
d) a flow-meter and a chronometer;
Possible detectors include the following:
— a photomultiplier associated with a sensitive scintillation surface [ZnS(Ag), for example];
— a silicon semi-conductor that is sensitive to alpha particles.
The detector, connected to a pulse counting system, shall have a sensitive detection surface at least equal in
diameter to the filtering membrane.
© ISO 2012 – All rights reserved 3

---------------------- Page: 15 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
a) Sampling system b) Detection system
Key
1 filtering membrane
2 filter holder
3 support
4 flow-meter and chronometer
5 pump
6 counting system
7 detector
Figure 1 — Functional diagram of a spot measuring system for potential alpha energy concentration
of short-lived radon decay products
6 Sampling
6.1 General
Grab sampling is representative of the potential alpha energy concentration of short-lived radon-222 decay
products at a given time and a given place.
6.2 Sampling objective
The sampling objective is to collect, without interruption, all the aerosols, regardless of their size (unattached
and attached fractions), carrying short lived radon decay products and contained in the ambient air during a
given sampling duration (less than one hour).
6.3 Sampling characteristics
The unattached and attached fractions of short-lived radon decay products shall be sampled without interruption
from the atmosphere under investigation by pumping and filtering a known volume of air through a high-
efficiency collection membrane located in an open filter holder. The air sampling shall be omni-directional.
In order to count the emitted alpha particles correctly, the sampling system shall conduct to the surface deposit
of the radionuclides on the filter and shall prevent the aerosols from being buried.
The sampling system shall be used in conditions that preclude clogging of the filtering membrane, which would
cause self-absorption of the alpha emissions of particles collected on the filter or a reduction in the sampling
flow-rate over time.
4 © ISO 2012 – All rights reserved

---------------------- Page: 16 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
6.4 Sampling conditions
6.4.1 General
Sampling shall be carried out as specified in ISO 11665-1. The sampling location, date and time shall be recorded.
6.4.2 Installation of sampling system
Installation of the sampling system shall be carried out as specified in ISO 11665-1.
6.4.3 Sampling duration
218
Given the short half-lives of the radon-222 decay products, particularly Po, the sampling duration should normally
be less than or equal to 20 min. A longer sampling duration would not improve the detection limit of the method.
6.4.4 Volume of air sampled
The volume of air sampled shall be ascertained by continuous measurement of the flow-rate during sampling
with a calibrated system (for example, a sonic nozzle) (see IEC 61577-3).
7 Detection method
Detection shall be performed using silver-activated zinc sulphide ZnS(Ag) scintillation or a semi-conductor
(alpha detection), as described in ISO 11665-1.
8 Measurement
8.1 Procedure
Measurement shall be carried out as follows.
a) Select the sampling duration, t .
s
b) Plan the counting stage, with n countings, and choose start time t and end time t for each number of
j cj
counts I . The different sets are organized from j = 1 to j = n. Before a set of counting, a specific waiting
j
time can be required.
NOTE Examples of gross alpha counting protocols are given in Annex A.
c) Install the detection system (detector and pulse counting system).
d) Determine the background level of the filtering membrane. Before carrying out sampling, position the
virgin membrane opposite the detector, in accordance with manufacturer recommendations. Measure the
virgin membrane by means of n successive gross alpha countings during specific counting durations t − t
cj j
according to the counting stage selected:
1) t = 0 to t = t standby, there is no count if t > 0;
1 1
2) t = t to t = t count I is performed;
1 c1 0,1
3) t = t to t = t standby, there is no count if t > t ;
cj−1 j j cj−1
4) t = t to t = t count I is performed.
j cj 0,j
If n > 1, repeat stages 3) and 4) until j = n.
e) Record values of I for j = 1 to j = n.
0,j
f) Select and locate the measuring point.
© ISO 2012 – All rights reserved 5

---------------------- Page: 17 ----------------------

SIST EN ISO 11665-3:2015
ISO 11665-3:2012(E)
g) Install the sampling system.
h) Using grab sampling, obtain an air sample representative of the atmosphere under investigation during the
sampling duration t .
s
i) Record the location and the time (date, hour and minutes) of sampling.
j) Once sampling is completed, remove the filtering membrane from the sampling system and position it opposite
the detector, in accordance with manufacturer recommendations. Given the short half-lives of the radon-222
decay products, the alpha particles shall be detected on the sampling site within a few minutes of sampling.
k) Perform n successive gross alpha countings of the membrane with specific counting durations t − t
cj j
according to the counting stage s
...