SIST EN ISO 20785-4:2026

• Abstract:

  This document is intended for the validation of codes used for the calculation of doses received by individuals on board aircraft. It gives guidance to radiation protection authorities and code developers on the basic functional requirements which the code fulfils.; Depending on any formal approval by a radiation protection authority, additional requirements concerning the software testing can apply.

• Status: Published
• Public Enquiry End Date: 30-Jul-2026
• Publication Date: 29-Sep-2026
• ICS: 13.280 - Radiation protection
• ICS: 49.020 - Aircraft and space vehicles in general
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 29-Sep-2026
• Due Date: 04-Dec-2026
• Completion Date: 30-Sep-2026
• Ref Project: EN ISO 20785-4:2026 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of codes (ISO 20785-4:2026)

• Revises: SIST EN ISO 20785-4:2021 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of codes (ISO 20785-4:2019)
• Effective Date: 21-May-2025

Overview

SIST EN ISO 20785-4:2026 covers the validation of codes used to calculate doses received by individuals on board civilian aircraft from cosmic radiation. This standard is part of the ISO 20785 series on dosimetry for exposures to cosmic radiation in civilian aircraft and focuses on helping radiation protection authorities and code developers confirm that software performs as intended.

The document is especially relevant where aircraft crew exposure assessment depends on calculation tools rather than direct measurement. It supports the use of validated software for estimating radiation exposure in aviation, with emphasis on practical verification against measured or reference data. Depending on formal approval by a radiation protection authority, additional software testing requirements may also apply.

Key Topics

This standard addresses the core elements needed for code validation in aviation dosimetry:

• Functional requirements for code validation
  • Guidance on what a code should fulfil before use in routine dose assessment
• Comparison with measured or reference data
  • Validation based on results from representative flight routes and radiation field conditions
• Use of operational quantities
  • Focus on ambient dose equivalent, H(10)*, as a practical benchmark for validating calculations linked to effective dose
• Routine dose assessment
  • Considerations for ongoing checks of correctness, reliability, traceability, and data quality
• Software testing expectations
  • Reference to structured testing practices and documentation of alternate methods where used
• Relevant flight data
  • Includes date and time in UTC, airports, flight levels, and available waypoints

The document also notes that it is intended for galactic cosmic radiation (GCR) and does not cover intermittent sources such as solar particle events or other exceptional radiation events.

Applications

SIST EN ISO 20785-4:2026 is useful for organizations involved in:

• Aircraft crew radiation protection
• Software development for aviation dosimetry
• Regulatory review and compliance
• Dose assessment tools used in civil aviation
• Validation of calculations against measured flight data

Typical practical use cases include:

• Verifying that a dose calculation code produces reliable results for representative routes
• Supporting radiation protection programs for airline crew
• Improving confidence in effective dose estimates derived from calculation methods
• Benchmarking software against ISO 20785 measurement methods and ICRU reference data

Related Standards

This document is closely connected to other parts of the ISO 20785 series and related testing standards:

• ISO 20785-1:2020 - Conceptual basis for measurements
• ISO 20785-2:2020 - Characterization of instrument response
• ISO 20785-3:2023 - Measurements at aviation altitudes
• ISO 80000-10:2019/Amd 1:2025 - Quantities and units
• ISO/IEC/IEEE 29119 (all parts) - Software testing
• ICRU Report 84 - Reference data for validation of cosmic-radiation doses
• ICRP Publication 132 - Radiological protection from cosmic radiation in aviation

For standards users seeking aviation radiation dosimetry, cosmic radiation exposure, and software validation, SIST EN ISO 20785-4:2026 provides a clear framework for dependable and reviewable dose calculation practices.

SLOVENSKI STANDARD
01-november-2026
Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem
prometu - 4. del: Kode za preverjanje veljavnosti (ISO 20785-4:2026)
Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of
codes (ISO 20785-4:2026)
Dosimetrie zu Expositionen durch kosmische Strahlung in Zivilluftfahrzeugen - Teil 4:
Validierung von Codes (ISO 20785-4:2026)
Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil - Partie 4:
Validation des codes (ISO 20785-4:2026)
Ta slovenski standard je istoveten z: EN ISO 20785-4:2026
ICS:
13.280 Varstvo pred sevanjem Radiation protection
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 20785-4
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2026
EUROPÄISCHE NORM
ICS 49.020 Supersedes EN ISO 20785-4:2021
English Version
Dosimetry for exposures to cosmic radiation in civilian
aircraft - Part 4: Validation of codes (ISO 20785-4:2026)
Dosimétrie pour l'exposition au rayonnement Dosimetrie zu Expositionen durch kosmische
cosmique à bord d'un avion civil - Partie 4: Validation Strahlung in Zivilluftfahrzeugen - Teil 4: Validierung
des codes (ISO 20785-4:2026) von Codes (ISO 20785-4:2026)
This European Standard was approved by CEN on 6 September 2026.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20785-4:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 20785-4:2026) has been prepared by Technical Committee ISO/TC 85 "Nuclear
energy, nuclear technologies, and radiological protection" in collaboration with 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 2027, and conflicting national standards shall
be withdrawn at the latest by March 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 20785-4:2021.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20785-4:2026 has been approved by CEN as EN ISO 20785-4:2026 without any
modification.
International
Standard
ISO 20785-4
Second edition
Dosimetry for exposures to cosmic
2026-09
radiation in civilian aircraft —
Part 4:
Validation of codes
Dosimétrie pour les expositions au rayonnement cosmique à bord
d'un avion civil —
Partie 4: Validation des codes
Reference number
ISO 20785-4:2026(en) © ISO 2026

ISO 20785-4:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 20785-4:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Quantities and units .2
3.2 Atmospheric radiation field .4
3.3 Software terms.5
4 General considerations . 5
5 Functionality . 5
5.1 General .5
5.2 Measured data .5
5.3 ICRU reference data.6
5.4 Code validation using measurements or reference data.6
5.5 Considerations for the routine dose assessment .6
Bibliography . 7

iii
ISO 20785-4:2026(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 document 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 85, Nuclear energy, nuclear technologies, and
radiological protection, Subcommittee SC 2, Radiological protection, in collaboration with the European
Committee for Standardization (CEN) Technical Committee CEN/TC 430, Nuclear energy, nuclear technologies,
and radiological protection, in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 20785-4:2019), of which it constitutes a minor
revision.
The main change is the revision of terms and definitions.
A list of all the parts in the ISO 20785 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 20785-4:2026(en)
Introduction
Aircraft crews are exposed to elevated levels of cosmic radiation of galactic and solar origin and secondary
radiation produced in the atmosphere, the aircraft structure and its contents. Following recommendations
[1]
of the International Commission on Radiological Protection (ICRP) in Publication 60 , the European Union
[2]
(EU) introduced a Basic Safety Standards Directive (BSS) which included exposure to natural sources of
ionizing radiation, including cosmic radiation, as occupational exposure for aircrew. International guidance
[3]
was also provided by the IAEA Safety Standards Series . This action was confirmed by ICRP Publications
[4] [5] [6]
103 and 132 , and the BSS was revised by EU.
[1] [4]
ICRP has defined the exposure to cosmic radiation as an existing exposure situation, because the source
exists before protection decisions can be made. In addition, exposure of aircraft crew to cosmic radiation is
[5]
occupational, and thus employers have a role to play in protection, even if options are limited in this case .
There is no contradiction in this, as occupational exposures can occur in existing exposure situations, and
this does not imply that protection measure cannot be planned.
The EU Directive requires account to be taken of the exposure of aircraft crew liable to receive more than
1 mSv per year. It then identifies the following four protection measures:
a) to assess the exposure of the crew concerned;
b) to take into account the assessed exposure when organising working schedules with a view to reducing
the doses of highly exposed crew;
c) to inform workers concerned with the health effects involved in their work;
d) to apply the same special protection during pregnancy to female crew in respect of the ‘child to be born’
as to other female workers.
The EU Council Directive should be incorporated into laws and regulations of EU Member States and would
be included in the aviation safety standards and procedures of the European Air Safety Agency. Other
[7] [8]
countries, such as Canada and Japan , have issued advisories to their airline industries to manage aircraft
crew exposure.
For regulatory and legislative purposes, the radiation protection quantities of interest are dose to the foetus
and effective dose. The cosmic radiation exposure of the body is essentially uniform and the maternal
abdomen provides no effective shielding to the foetus. As a result, the magnitude of equivalent dose to
the foetus can be put equal to that of the effective dose received by the mother. Doses on board aircraft
are generally predictable, and events comparable to unplanned exposure in other radiological workplaces
cannot normally occur (with the rare exceptions of extremely intense and energetic solar particle events).
Personal dosimeters for routine use are thus not needed nor practical. The preferred approach for the
assessment of doses of aircraft crew, where necessary, is to calculate directly the effective dose rate, as
a function of geographic location, altitude and solar cycle phase, and to fold these values with flight and
staff roster information to obtain estimates of effective doses for individuals. This approach is supported by
[9] [5] [10]
guidance from the ICRP in Publication 75 and Publication 132 , and the ICRU in Report 84 .
The role of calculations in this procedure is unique in routine radiation protection and it is widely accepted
that the calculated doses should be validated by measurement. Effective dose is not directly measurable.
The operational quantity of interest is ambient dose equivalent, H*(10). Indeed, as indicated in particular
in ICRU Report 84, the ambient dose equivalent is considered to be a conservative estimator of effective
dose if isotropic irradiation can be assumed. In order to validate the assessed doses obtained in terms of
effective dose, calculations can be made of ambient dose equivalent rates or route doses in terms of ambient
dose equivalent, and the results can be compared to measurements traceable to national standards. The
validation of calculations of ambient dose equivalent for a particular calculation method may be taken as
a validation of the calculation of effective dose by the same code. The alternative is to establish, a priori,
that the operational quantity ambient dose equivalent is a good estimator of effective dose and equivalent
dose to the foetus for the radiation fields being considered, in the same way that the use of the operational
quantity personal dose equivalent is justified for the estimation of effective dose for radiation workers.

v
ISO 20785-4:2026(en)
The route dose is the best estimate of ambient dose equivalent for the actual route recorded for the aircrew.
However, the actual route flown for that specific flight may vary due to weather, scheduling, etc.
It should be noted that this document addresses galactic cosmic radiation (GCR) only. First discovered by
Victor Hess more than 100 years ago, GCR is a well understood and permanent source o
...