kSIST FprEN 1422:2026

• Abstract:

  1.1 This document specifies the requirements and the relevant tests for automatically controlled sterilizers employing ethylene oxide (EO) gas as the sterilant, either as a pure gas or a mixture with other gases (for example carbon dioxide or nitrogen) being used for the sterilization of medical devices and their accessories.; 1.2 This document specifies requirements for ethylene oxide sterilizers (EO sterilizers) for:; — the performance and design of sterilizers intended to deliver a process capable of sterilizing medical devices;; — the equipment and controls of these sterilizers, needed for operation, control and monitoring of the sterilization processes;; — the test equipment and test procedures used to verify the sterilizer performance specified by this document.; 1.3 This document does not cover sterilizers which employ the injection of EO or mixtures containing EO directly into packages or into a flexible chamber.

• Status: Not Published
• Public Enquiry End Date: 29-Jun-2025
• ICS: 11.080.10 - Sterilizing equipment
• Technical Committee: VAZ - Healthcare
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 04-Sep-2026
• Due Date: 23-Oct-2026
• Completion Date: 07-Sep-2026
• Directive: 2017/745 - Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, amending Directive 2001/83/EC, Regulation (EC) No 178/2002 and Regulation (EC) No 1223/2009 and repealing Council Directives 90/385/EEC and 93/42/EEC
• Mandate: M/575 - Medical devices in support of Regulation (EU) 2017/745 and in vitro diagnostic medical devices in support of Regulation (EU) 2017/746
• Mandate: M/575 AMD 2 - Medical devices in support of Regulation (EU) 2017/745 and in vitro diagnostic medicial devices in support of Regulation (EU) 2017746
• Ref Project: FprEN 1422 - Sterilizers for medical purposes - Ethylene oxide sterilizers - Requirements and test methods

• Revises: SIST EN 1422:2014 - Sterilizers for medical purposes - Ethylene oxide sterilizers - Requirements and test methods
• Effective Date: 30-Aug-2023

kSIST FprEN 1422:2026 is a SIST draft European standard for sterilizers for medical purposes. It specifies requirements and test methods for automatically controlled ethylene oxide (EO) sterilizers used to sterilize medical devices and their accessories. In practice, it tells manufacturers, test laboratories, and users what the sterilizer design, controls, measurements, records, and verification tests need to cover.

What does kSIST FprEN 1422:2026 specify?

kSIST FprEN 1422:2026 applies to automatically controlled sterilizers that use EO gas as the sterilant, either as a pure gas or mixed with other gases such as carbon dioxide or nitrogen. It covers the performance and design of the sterilizer, the equipment and controls needed to operate and monitor the process, and the test equipment and test procedures used to verify performance.

The document is organized into clauses 1 to 12, followed by annexes A to I and Annex ZA. The main clauses cover scope, normative references, terms and definitions, general requirements, design and construction, indicating and recording devices, services, emissions, test instrumentation, performance and assessment, information to be supplied, and packaging.

Annex	What it covers
A	Test programme for type tests, works tests, acceptance test upon installation, and installation qualification provisions
B	Leak test cycle
C	Sterilizer chamber profile testing
D	Microbiological performance test for EO sterilizers
E	Environmental aspects
F	Illustrations of the interrelationship between control and recording
G	Additional information on protective measures
H	Test instrumentation
I	Example stages used in an EO sterilization cycle and guidance on their purpose
ZA	Relationship with Regulation (EU) 2017/745

The scope excludes sterilizers that inject EO or EO mixtures directly into packages or into a flexible chamber.

What are the key requirements of kSIST FprEN 1422:2026?

kSIST FprEN 1422:2026 is built around risk-based design, controlled cycle execution, measurable performance, and documented information for users. For a buyer or engineer, the practical message is simple: the sterilizer has to be safe to operate, able to reproduce the process it claims, and equipped so that its performance can be checked.

Safety, access, and chamber design

• Clause 4 requires the sterilizer type to be defined in the technical documentation, and any alteration to be reviewed with risk assessment. This matters because changes to the design can affect sterilization performance or safety.
• Clause 5 requires the design to address safety and security, including protection against unauthorized access. That is important because access to controls or internal parts can affect both patient safety and operator safety.
• Clause 5.2.2 requires chamber doors and interlocks that prevent opening during an operating cycle. Double-ended sterilizers also need clear door-status indication and locking logic so loading and unloading sides cannot be confused.
• Clause 5.2.4 ties pressure vessels and steam boilers to the referenced vessel and boiler standards. In practice, the chamber and any pressure-bearing parts must be built and verified to the appropriate pressure-equipment rules.
• Clause 5.3 covers pipework, vaporizers, evacuation systems, framework, panelling, and loading equipment. These requirements matter because EO has to be distributed, evacuated, and removed without leaks, condensate build-up, or unsafe access.

Control, monitoring, and records

• Clause 6 requires an automatic controller with permanently stored pre-set programmes. The cycle must be repeatable, not manually improvised from run to run.
• Clause 6.3 requires separate measuring chains and segregated software functions for control, independent data collection, and failure detection. This separation matters because the recorded process data must be trustworthy, not just whatever the controller is using internally.
• Clause 6.4 defines how faults and failures are handled. If a critical failure occurs, the load is treated as non-sterile until the defined response has been completed.
• Clause 6.5 and Clause 6.6 require instrumentation and indication for cycle variables such as temperature, pressure, time, EO concentration, and relative humidity (RH). Clause 6.7 requires the records to be retained and retrievable, in electronic or printed form.
• Clause 6.8 and Annex I describe the cycle stages, including air removal, automatic leak rate testing, conditioning if used, EO exposure, EO holding time, EO removal, desorption, air admission, cycle complete, and aeration. This helps users understand what the machine is doing and what to check in each phase.

Performance, testing, and utilities

• Clause 10 requires type testing with reference loads and performance assessment across the usable chamber space. The standard is not just about one chamber setting - it checks whether the process works throughout the space where the load sits.
• Clause 10.2 and Annex B cover chamber integrity and the leak test cycle. That matters because leakage can disturb cycle conditions and can also allow re-contamination after the cycle.
• Clause 10.3 and Annex C require chamber profile testing for empty and loaded conditions, including temperature and pressure behavior. This shows whether the chamber reaches and maintains the intended conditions.
• Clause 10.4 and Annex D set the microbiological performance test. The cycle has to achieve a probability of survival of a single microorganism of not greater than 1 x 10^-6.
• Clause 10.5 and 10.6 address EO removal and aeration so residual EO reaches the required level. Clause 10.8 requires the load to be arranged so gas circulation is adequate and the load does not contact heated or cooled surfaces.
• Clause 7 specifies the services the sterilizer depends on - EO, electrical supply, water, steam, vacuum, drains, lighting, compressed air, air and inert gases, and ventilation. For installation planning, this is where you check whether the site can support the machine.
• Clauses 8, 11, and 12 cover emissions, information to be supplied, and packaging. That includes electromagnetic emissions, noise, exhaust emissions, heat emission, marking, labels, instructions for use, and transport packaging.

What terms does kSIST FprEN 1422:2026 define?

• Access device - Means used to reach restricted parts of the equipment, such as a key, code, or tool.
• Aeration - The part of the process in which EO or its reaction products desorb from the product until predetermined levels are reached.
• Automatic controller - The device that moves the equipment through the required cycle stages according to programmed cycle parameters.
• Biological indicator [BI] - A test system containing viable microorganisms with specified resistance to a specified sterilization process.
• Calibration - The operation that links measurement standards to instrument indications and uses that link to obtain a measurement result.
• Chamber - The part of the equipment in which a load is processed.
• Conditioning - Treatment of the load before exposure so that temperature, RH, or another process variable reaches the specified level throughout the load.
• Cycle parameter - A cycle-variable value, including tolerance, used for control, monitoring, indication, and recording of an operating cycle.
• Fault - A situation where one or more process or cycle parameters are outside their specified limits.

Who uses kSIST FprEN 1422:2026?

kSIST FprEN 1422:2026 is used by manufacturers of EO sterilizers, because it tells them how to design the equipment, its controls, and its test interfaces. It is also used by validation and qualification teams, who need a common basis for type tests, works tests, installation checks, leak tests, and microbiological performance testing.

Quality and regulatory staff use it to prepare technical documentation, labels, instructions for use, and conformity evidence. Buyers and technical evaluators use it to compare chamber size, utilities, emissions, packaging, and installation requirements before purchase.

It is relevant in health care facilities and industrial settings, and the introduction notes medical, dental, pharmaceutical, veterinary, industrial, and other related purposes.

What changed in kSIST FprEN 1422:2026 from the previous edition?

kSIST FprEN 1422:2026 will supersede EN 1422:2014. The foreword states that the main technical changes are:

• the structure of the main text has been adapted to ISO/TS 22421:2021 and harmonized with the current revisions of EN 17180 and EN 14180;
• references have been updated, including Table E.1 and the bibliography;
• several terms have been added, and most definitions have been adapted with reference to EN ISO 11139:2018/A1:2024;
• a separate clause on protective measures has been added to support references to EN IEC 61010-2-040:2021;
• a new informative Annex G has been added;
• the control and monitoring requirements have been merged into a new clause, with explanatory illustrations moved into a new Annex F.

Which standards are used with kSIST FprEN 1422:2026?

Standard	What it contributes
EN ISO 11135:2014	Process development, validation, routine control, and references to PQ / MPQ
EN IEC 61010-2-040:2021	Safety requirements and protective measures for sterilizers and washer-disinfectors
EN IEC 61326-1:2021	EMC immunity and electromagnetic emissions
EN ISO 12100:2010	Risk assessment and risk reduction for machinery design
EN ISO 14971:2019	Medical-device risk management
EN 62366-1:2015	Usability engineering for medical devices
EN 61511-1:2017	Functional safety framework for safety-related systems
EN ISO 11138-1:2017 and EN ISO 11138-2:2017	Biological indicators, including EO indicators
EN ISO 11607-1:2020, EN 868-4:2017, EN 868-5:2018	Packaging and sterile barrier systems for test loads and products
EN ISO 10993-7:2008	EO residuals after sterilization and aeration
EN ISO 3746:2010	Noise measurement
EN 13445-1, -2, -3, -4, -5, -8 and EN 764-7	Pressure-vessel and pressure-equipment design, fabrication, inspection, and safety systems
EN 14222:2021	Stainless steel steam boilers used as part of the sterilizer
EN ISO 15223-1:2021	Symbols for information supplied by the manufacturer
EN ISO 3166-1:2020, ISO 639:2023, ISO 8000-1:2022, ISO 8573-1:2010, ISO 8601-1:2019	Country codes, language codes, data quality, compressed-air purity, and date/time format
ISO/TS 22421:2021	Basis for the informative control-and-recording illustrations in Annex F
EN ISO 11139:2018/A1:2024	Source terminology for many defined terms in Clause 3

What does the kSIST FprEN 1422:2026 document contain?

kSIST FprEN 1422:2026 contains a full test and requirements framework for EO sterilizers. It gives the recommended test programme in Table A.1, the leak test cycle in Annex B, chamber profile testing methods in Annex C, and the microbiological performance test in Annex D.

It also includes Annex H for test instrumentation, so laboratories know what accuracy, response time, and recording capability the test equipment needs. Annex I describes the stages of an EO cycle and Figure I.1 shows an example pressure profile for a sub-atmospheric cycle.

For documentation and user information, the document includes requirements for marking, labelling, instructions for use, transport packaging, and installation information. Annex E summarizes environmental aspects, Annex F explains control and recording relationships, and Annex ZA links the standard to the General Safety and Performance Requirements of Regulation (EU) 2017/745.

SLOVENSKI STANDARD
oSIST prEN 1422:2025
01-junij-2025
Sterilizatorji za uporabo v medicini - Sterilizatorji z etilenoksidom - Zahteve in
preskusne metode
Sterilizers for medical purposes - Ethylene oxide sterilizers - Requirements and test
methods
Sterilisatoren für medizinische Zwecke - Ethylenoxid-Sterilisatoren - Anforderungen und
Prüfverfahren
Stérilisateurs à usage médical - Stérilisateurs à l'oxyde d'éthylène - Exigences et
méthodes d'essai
Ta slovenski standard je istoveten z: prEN 1422
ICS:
11.080.10 Sterilizacijska oprema Sterilizing equipment
oSIST prEN 1422:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 1422:2025
oSIST prEN 1422:2025
DRAFT
EUROPEAN STANDARD
prEN 1422
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2025
ICS 11.080.10 Will supersede EN 1422:2014
English Version
Sterilizers for medical purposes - Ethylene oxide
sterilizers - Requirements and test methods
Stérilisateurs à usage médical - Stérilisateurs à l'oxyde Sterilisatoren für medizinische Zwecke - Ethylenoxid-
d'éthylène - Exigences et méthodes d'essai Sterilisatoren - Anforderungen und Prüfverfahren
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 102.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1422:2025 E
worldwide for CEN national Members.

oSIST prEN 1422:2025
prEN 1422:2025 (E)
Contents Page
European foreword . 6
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 10
4 General. 17
4.1 Product definition. 17
4.2 Equipment development . 17
4.3 Calibration . 18
5 Equipment design and construction . 18
5.1 Safety and security . 18
5.1.1 General. 18
5.1.2 Protective measures . 19
5.1.3 Risk control and usability . 21
5.2 Sterilizer chamber . 21
5.2.1 Dimensions. 21
5.2.2 Doors and interlocks of the sterilizer chamber . 22
5.2.3 Chamber integrity . 23
5.2.4 Pressure vessels . 24
5.2.5 Uniformity of conditions, temperature control and insulating the sterilizer chamber . 24
5.3 Further functional components . 24
5.3.1 Pipework and fittings . 24
5.3.2 Vaporizers . 25
5.3.3 Evacuation system . 25
5.3.4 Framework and panelling . 26
5.3.5 Loading Equipment . 27
5.4 Materials . 27
5.4.1 Chamber materials . 27
5.4.2 Other materials used in the construction of the sterilizer . 27
5.5 Test connections . 28
5.6 Vibration . 29
5.7 User interfaces . 29
5.8 Transport . 30
6 Indicating, monitoring, controlling and recording devices . 31
6.1 General. 31
6.1.1 General. 31
6.1.2 Pre-set programme . 31
6.1.3 Automatic controller . 31
6.2 Automatic control . 31
6.3 Control and monitoring system . 33
6.4 Failure . 34
6.4.1 General. 34
6.4.2 Fault . 35
6.4.3 Power failure . 36
oSIST prEN 1422:2025
prEN 1422:2025 (E)
6.4.4 Other failures . 36
6.5 Instrumentation . 36
6.5.1 General . 36
6.5.2 Temperature measuring devices . 37
6.5.3 Pressure measuring devices . 39
6.5.4 Time measuring devices . 40
6.5.5 Sterilizing agent control and measuring devices . 40
6.5.6 Relative humidity (RH) sensors . 41
6.6 Indicating devices . 41
6.6.1 General . 41
6.6.2 Cycle parameter indicating devices . 41
6.6.3 Cycle parameter indications . 43
6.6.4 Status indicators and indications . 43
6.6.5 Operating cycle counter . 44
6.7 Recorders . 45
6.7.1 General . 45
6.7.2 Records . 46
6.7.3 Analogue presentation of records . 47
6.7.4 Digital records . 47
6.8 Operating cycles . 48
6.8.1 General . 48
6.8.2 Maintenance leak test . 48
6.8.3 Sterilization cycles . 49
7 Services and local environment . 51
7.1 General . 51
7.2 Sterilizing agent and sterilant . 52
7.3 Electrical supply . 53
7.4 Water . 53
7.5 Steam . 54
7.6 Vacuum . 54
7.7 Drains . 54
7.8 Lighting . 55
7.9 Compressed air . 55
7.10 Air and inert gases. 55
7.11 Ventilation . 56
8 Emissions . 56
8.1 Electromagnetic emissions . 56
8.2 Noise . 56
8.3 Exhaust emissions . 57
8.4 Heat emission . 58
9 Test instrumentation . 58
10 Performance and assessment . 58
10.1 General . 58
10.2 Chamber integrity . 59
10.3 Attainment of conditions; physical parameters . 60
10.3.1 Heating of the sterilizer chamber internal surfaces . 60
10.3.2 Temperature profile for an empty sterilizer chamber . 60
10.3.3 Pressure profile and pressure change . 60
10.3.4 Sterilizing agent and sterilant . 61
10.4 Microbiological performance . 61
10.5 EO removal (flushing) . 61
oSIST prEN 1422:2025
prEN 1422:2025 (E)
10.6 Aeration . 61
10.7 Load dryness . 61
10.8 Loading configuration . 62
11 Information to be supplied . 62
11.1 General. 62
11.2 Information to be made available prior to purchase . 62
11.3 Marking and labelling . 64
11.4 Labelling . 65
11.5 Instructions for use . 65
12 Packaging . 67
Annex A (informative)  Test programme . 68
A.1 General. 68
A.2 Type test . 68
A.3 Works test . 68
A.4 Tests programme . 68
A.5 Acceptance test upon installation . 70
A.6 Installation qualification (IQ) provisions . 70
Annex B (normative) Leak test cycle. 71
Annex C (normative) Sterilizer chamber profile testing . 72
C.1 Sterilizer chamber internal surfaces . 72
C.2 Empty sterilizer chamber . 72
Annex D (normative) Microbiological performance test for EO sterilizers . 74
D.1 General. 74
D.2 Apparatus . 74
D.3 Procedure . 75
D.4 Interpretation of results . 75
Annex E (informative) Environmental aspects . 77
E.1 Environmental aspects regarding the life cycle of EO sterilizers . 77
E.2 EO . 77
E.3 Environmental impact . 77
Annex F (informative)  Illustrations of the interrelationship between control and recording . 79
F.1 Introduction . 79
F.2 Illustration 1 . 81
F.3 Illustration 2 . 82
F.4 Illustration 3 . 83
Annex G (informative)  Additional information on protective measures . 86
Annex H (normative) Test Instrumentation . 87
Annex I (informative) Example of the stages used in an EO sterilization cycle and guidance on
their purpose. . 89
oSIST prEN 1422:2025
prEN 1422:2025 (E)
I.1 General . 89
I.2 Stage 0: Chamber pre-heating/cooling . 89
I.3 Stage 1: Air removal . 89
I.4 Stage 2: Automatic Leak Rate Test (ALRT) . 89
I.5 Stage 3: conditioning (if used) . 90
I.6 Stage 4: EO exposure . 90
I.7 Stage 5: EO holding time . 90
I.8 Stage 6: EO removal . 90
I.9 Stage 7: Desorption . 90
I.10 Stage 8: Air admission . 90
I.11 Stage 9: Cycle complete. 91
I.12 Stage 10: Aeration . 91
Annex ZA (informative) Relationship between this European Standard and the General Safety
and Performance Requirements of Regulation (EU) 2017/745 aimed to be covered. 92
Bibliography . 114

oSIST prEN 1422:2025
prEN 1422:2025 (E)
European foreword
This document (prEN 1422:2025) has been prepared by Technical Committee CEN/TC 102 “Sterilizers
and associated equipment for processing of medical devices”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1422:2014.
In comparison with the previous edition, the following technical modifications have been made:
— structure of the main text has been adapted to the structure of ISO/TS 22421:2021 and harmonized
with the current revisions of EN 17180 and EN 14180;
— references have been updated, including Table E.1 on Environmental Aspects, and the bibliography;
— some definitions of terms have been added, most definitions have been adapted with reference to
EN ISO 11139:2018/A1:2024;
— a separate clause ‘Protective measures’ has been implemented for referencing to individual clauses
of EN IEC 61010-2-040:2021;
— a new Annex G ‘Additional information on protective measures’ has been added;
— requirements on the control and monitoring system have been merged into a new clause and
informative illustrations including some explanations have been provided in a new Annex F.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
In this document, the following verbal forms are used:
— “shall” indicates a requirement;
— “should” indicates a recommendation;
— “may” indicates a permission;
— “can” indicates a possibility or capability; and
— "must" is used to express an external constraint.
In this document notes are used for giving additional information intended to assist the understanding
or use of the text. The document is usable without the notes.
oSIST prEN 1422:2025
prEN 1422:2025 (E)
Introduction
This document provides minimum requirements and test methods for sterilizers performing a low
temperature ethylene oxide (EO) sterilization process.
Ethylene oxide (EO) sterilizers employ EO gas as the sterilant, either as a pure gas or in admixture with
other gases (e.g. carbon dioxide). When used as a pure gas the gas exposure stage is usually carried out
at sub-atmospheric pressures. When used as an admixture the gas exposure stage is usually carried out
at super-atmospheric pressures. Ethylene oxide sterilization processes are primarily used for the

sterilization of heat labile products at temperatures less than 60 °C.
EO is a highly reactive chemical which can present a toxicity, flammability or explosive hazard if
incorrectly handled (see Annex E).
The EO sterilizer specified in this document can be used for medical, dental, pharmaceutical, veterinary,
industrial or other related purposes in health care facilities or industrial settings.
The equipment related tests described in this document are reference tests intended for use in
demonstrating conformity with the performance requirements specified in this document. They may be
used in type tests, works tests, in validation and re-validation tests, or in periodic and routine tests
carried out by the user. Validation and routine control of sterilization processes are essential to ensure
their efficacy. This document does not cover validation and routine control of EO sterilization processes.
Such activities are covered in EN ISO 11135:2014.
EO sterilizers should not be assumed to deliver processes effectively inactivating the causative agents of
spongiform encephalopathies such as scrapie, Bovine Spongiform Encephalopathy and Creutzfeldt-Jakob
Disease. Specific recommendations have been produced in particular countries for the processing of
materials potentially contaminated with these agents. See also EN ISO 11135:2014, 1.2.
Planning and design of sterilizers complying with this document should consider not only technical issues
but also the environmental impact from the use of the sterilizer during its life cycle. Environmental
aspects are addressed in Annex E of this document.
By performing tests concurrently and/or in a logical succession, the total number of tests and consumable
test equipment disposals is reduced. As a result, the burden on the environment can be reduced (see also
Annex E).
This document is not intended as a checklist for the suitability of an existing EO sterilizer when assessing
compliance with EN ISO 11135:2014. This standard is not intended to be applied retrospectively.
This document does not cover analytical methods for determining levels of residual EO and/or its
reaction products. Analytical methods for determining levels of residual EO and/or its reaction products
are addressed in ISO 10993-7:2008.
General equipment safety requirements are specified in EN 61010-1:2010, EN IEC 61010-2-040:2021
and EN 60204-1:2018 and can provide valuable information on design options. They are referenced
herein, but not repeated.
Occupational safety is not addressed in this document.
oSIST prEN 1422:2025
prEN 1422:2025 (E)
1 Scope
1.1 This document specifies the requirements and the relevant tests for automatically controlled
sterilizers employing ethylene oxide (EO) gas as the sterilant, either as a pure gas or a mixture with other
gases, being used for the sterilization of medical devices and their accessories.
1.2 This document specifies requirements for ethylene oxide sterilizers (EO sterilizers) for:
— the performance and design of sterilizers intended to deliver a process capable of sterilizing medical
devices;
— the equipment and controls of these sterilizers, needed for operation, control and monitoring of the
sterilization processes;
— the test equipment and test procedures used to verify the sterilizer performance specified by this
document.
1.3 This document does not cover sterilizers which employ the injection of EO or mixtures containing EO
directly into packages or into a flexible chamber.
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.
EN 764-7:2002, Pressure equipment - Part 7: Safety systems for unfired pressure equipment
EN 868-4:2017, Packaging for terminally sterilized medical devices - Part 4: Paper bags - Requirements and
test methods
EN 868-5:2018, Packaging for terminally sterilized medical devices - Part 5: Sealable pouches and reels of
porous materials and plastic film construction - Requirements and test methods
EN 13445-1:2021, Unfired pressure vessels - Part 1: General
EN 13445-2:2021+A1:2023, Unfired pressure vessels - Part 2: Materials
EN 13445-3:2021, Unfired pressure vessels - Part 3: Design
EN 13445-4:2021+A1:2023, Unfired pressure vessels - Part 4: Fabrication
EN 13445-5:2021+A1:2024, Unfired pressure vessels - Part 5: Inspection and testing
EN 13445-8:2021, Unfired pressure vessels - Part 8: Additional requirements for pressure vessels of
aluminium and aluminium alloys
EN 14222:2021, Stainless steel steam boilers
EN 60073:2002, Basic and safety principles for man-machine interface, marking and identification - Coding
principles for indicators and actuators (IEC 60073:2002)
EN IEC 61010-2-040:2021, Safety requirements for electrical equipment for measurement, control and
laboratory use — Part 2-040: Particular requirements for sterilizers and washer-disinfectors used to treat
medical materials (IEC 61010-2-040:2020)
oSIST prEN 1422:2025
prEN 1422:2025 (E)
EN 61511-1:2017, Functional safety - Safety instrumented systems for the process industry sector - Part 1:
Framework, definitions, system, hardware and application programming Requirements (IEC 61511-1:2016
+ COR1:2016)
EN 62366-1:2015, Medical devices Part 1: Application of usability engineering to medical devices (IEC
62366-1:2015)
EN IEC 61326-1:2021, Electrical equipment for measurement, control and laboratory use - EMC
requirements — Part 1: General requirements (IEC 61326-1:2020)
EN ISO 3166-1:2020, Codes for the representation of names of countries and their subdivisions - Part 1:
Country code (ISO 3166-1:2020)
EN ISO 3746:2010, Acoustics - Determination of sound power levels and sound energy levels of noise sources
using sound pressure - Survey method using an enveloping measurement surface over a reflecting plane (ISO
3746:2010)
EN ISO 10993-7:2008, Biological evaluation of medical devices - Part 7: Ethylene oxide sterilization
residuals (ISO 10993-7:2008)
EN ISO 11135:2014, Sterilization of health-care products — Ethylene oxide — Requirements for the
development, validation, and routine control of a sterilization process for medical devices (ISO 11135:2014)
EN ISO 11138-1:2017, Sterilization of health care products - Biological indicators - Part 1: General
requirements (ISO 11138-1:2017)
EN ISO 11138-2:2017, Sterilization of health care products - Biological indicators - Part 2: Biological
indicators for ethylene oxide sterilization processes (ISO 11138-2:2017)
EN ISO 11607-1:2020, Packaging for terminally sterilized medical devices - Part 1: Requirements for
materials, sterile barrier systems and packaging systems (ISO 11607-1:2019)
EN ISO 12100:2010, Safety of machinery - General principles for design- Risk assessment and risk reduction
(ISO 12100:2010)
EN ISO 14971:2019, Medical devices - Application of risk management to medical devices (ISO
14971:2019)
EN ISO 15223-1:2021, Medical devices - Symbols to be used with information to be supplied by the
manufacturer - Part 1: General requirements (ISO 15223-1:2021)
ISO 639:2023, Code for individual languages and language groups
ISO 8000-1:2022, Data quality - Part 1: Overview
ISO 8573-1:2010, Compressed air - Part 1: Contaminants and purity classes
ISO 8601-1:2019, Date and time - Representations for information interchange - Part 1: Basic rules

As impacted by EN 61511-1:2017/A1:2017.
As impacted by EN 62366-1:2015/AC:2015/A1:2020.
As impacted by EN ISO 10993-7:2008/AC:2009/A1:2022.
As impacted by EN ISO 11135:2014/A1:2019.
As impacted by EN ISO 11607-1:2020/A1:2023.
As impacted by EN ISO 14971:2019/A11:2021.
As impacted by ISO 8601-1:2019/AMD 1:2022.
oSIST prEN 1422:2025
prEN 1422:2025 (E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/
3.1
access device
means by which entry to restricted parts of equipment is achieved
Note 1 to entry: This can be by dedicated key, code, or tool.
Note 2 to entry: There is likely to be more than one access device all of which can be different depending on
function.
[SOURCE: EN ISO 11139:2018/A1:2024, 3.4, modified — Notes 1 and 2 to entry added.]
3.2
aeration
part of the sterilization process during which either the sterilizing agent or its reaction products, or both,
desorb from the health care product until predetermined levels are reached
Note 1 to entry: This can be performed within the sterilization chamber or in a separate chamber or room.
[SOURCE: EN ISO 11135: 2014, 3.7, modified — Note 1 to entry added and changed “sterilization cycle”
to “sterilization process”.]
3.3
automatic controller
device that directs the equipment sequentially through required stages of the cycle in response to
programmed cycle parameters
[SOURCE: EN ISO 11139:2018/A1:2024, 3.18]
3.4
biological indicator
test system containing viable microorganisms providing a specified resistance to a specified sterilization
process
[SOURCE: EN ISO 11139:2018/A1:2024, 3.29]
3.5
calibration
operation that, under specified conditions, in a first step, establishes a relation between the quantity
values with measurement uncertainties provided by measurement standards and corresponding
indications with associated measurement uncertainties and, in a second step, uses this information to
establish a relation for obtaining a measurement result from an indication
[SOURCE: EN ISO 11139:2018/A1:2024, 3.31]
oSIST prEN 1422:2025
prEN 1422:2025 (E)
3.6
chamber
part of equipment in which a load is processed
[SOURCE: EN ISO 11139:2018/A1:2024]
3.7
conditioning
treatment of load prior to the exposure phase to attain a specified temperature, relative humidity, or
other process variable throughout the load
[SOURCE: EN ISO 11139:2018/A1:2024, 3.58, modified — “product” is changed to “load”.]
3.8
control
regulation of variables within specified limits
[SOURCE: EN ISO 11139:2018/A1:2024, 3.63]
3.9
cycle complete
message from the automatic controller that the operating cycle has ended successfully
Note 1 to entry: Upon indication of “cycle complete” in the sterilizer, the processed load can need a period of
aeration using a separate operating cycle or in a separate chamber.
[SOURCE: EN ISO 11139:2018/A1:2024, 3.71, modified — Note 1 to entry has been added.]
3.10
cycle parameter
value of a cycle variable including its tolerance used for control, monitoring, indication, and recording of
an operating cycle
Note 1 to entry: See also 3.24, process parameter.
[SOURCE: EN ISO 11139:2018/A1:2024, 3.72, modified — Note 1 to entry added.]
3.11
cycle variable
property used to control, monitor, indicate, or record an operating cycle
Note 1 to entry: Process variables that are used by the automatic controller to control, monitor, indicate or record
are also cycle variables, so a cycle variable can also be a process variable, e.g. time.
Note 2 to entry: Pressure can be a cycle variable.
Note 3 to entry: See also 3.26, process variable.
[SOURCE: EN ISO 11139:2018/A1:2024, 3.74, modified — Note 1, 2 and 3 to entry has been added.]
3.12
double-ended
having separate doors for loading and unloading in separate areas
[SOURCE: EN ISO 11139:2018/A1:2024, 3.92, modified — Note 1 to entry deleted.]
oSIST prEN 1422:2025
prEN 1422:2025 (E)
3.13
exposure stage
cycle stage between the introduction of the sterilizing or disinfecting agent into the chamber and when
its microbicidal effect has become negligible
Note 1 to entry: The exposure stage comprises that part of the process for which microbial lethality is claimed.
[SOURCE: EN ISO 11139:2018/A1:2024, 3.111]
3.14
fault
situation in which one or more of the process or cycle parameters is/are outside its/their specified
tolerance(s)
[SOURCE: EN ISO 11139:2018/A1:2024, 3.116]
3.15
flushing
purging
removing by displacement with a fluid
[SOURCE: EN ISO 11139:2018/A1:2024, 3.121]
3.16
indicate
display a value, condition, or stage of process
[SOURCE: EN ISO 11139:2018/A1:2024, 3.139]
3.17
load
product, equipment, or materials to be processed together within an operation cycle
[SOURCE: EN ISO 11139:2018/A1:2024, 3.155]
3.18
maximum allowable working pressure
MAWP
maximum pressure to which a component is designed to be subjected to and which is the basis for
determining the strength of the component under consideration
Note 1 to entry: The maximum pressure which can be applied to a specified product without compromising safety,
quality or performance can be given in the process specification.
3.19
measuring chain
series of elements of a measuring instrument measuring system, which constitutes the path of the
measurement signal from the input (quantity subject to measurement) to the output (the result of the
measurement)
[SOURCE: EN ISO 11139:2018/A1:2024, 3.165]
oSIST prEN 1422:2025
prEN 1422:2025 (E)
3.20
medical device
instrument, apparatus, implement, machine, appliance, implant, reagent for in vitro use, or software
material, or other similar or related article, intended by the manufacturer to be used, alone or in
combination, for human beings, for one or more of the specific medical purpose(s) of:
— diagnosis, prevention, monitoring, treatment, or alleviation of disease;
— diagnosis, monitoring, treatment, alleviation of, or compensation for an injury;
— investigation, replacement, modification, or support of the anatomy, or of a physiological process;
— supporting or sustaining life;
— control of conception;
— disinfection of medical devices;
— providing information by means of in vitro examination of specimens derived from the human body;
and does not achieve its primary intended action by pharmacological, immunological, or metabolic
means, in or on the human body, but which may be assisted in its intended function by such means
Note 1 to entry: Products which may be considered to be medical devices in some jurisdictions, but not in others
include:
— items
...