SIST EN ISO 7396-3:2025

SLOVENSKI STANDARD
01-september-2025
Sistemi napeljav za medicinske pline - 3. del: Proporcionalne enote za proizvodnjo
sintetičnega medicinskega zraka (ISO 7396-3:2025)
Medical gas pipeline systems - Part 3:Proportioning units for the production of synthetic
medical air (ISO 7396-3:2025)
Rohrleitungssysteme für medizinische Gase - Teil 3: Gasmischersysteme für die
Herstellung von synthetischer medizinischer Luft (ISO 7396-3:2025)
Systèmes de distribution de gaz médicaux - Partie 3: Unités mélangeurs pour la
production d'air médical reconstitué (ISO 7396-3:2025)
Ta slovenski standard je istoveten z: EN ISO 7396-3:2025
ICS:
11.040.10 Anestezijska, respiratorna in Anaesthetic, respiratory and
reanimacijska oprema reanimation equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 7396-3
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2025
EUROPÄISCHE NORM
ICS 11.040.10
English Version
Medical gas pipeline systems - Part 3:Proportioning units
for the production of synthetic medical air (ISO 7396-
3:2025)
Systèmes de distribution de gaz médicaux - Partie 3: Rohrleitungssysteme für medizinische Gase - Teil 3:
Unités mélangeurs pour la production d'air médical Gasmischersysteme für die Herstellung von
reconstitué (ISO 7396-3:2025) synthetischer medizinischer Luft (ISO 7396-3:2025)
This European Standard was approved by CEN on 28 June 2025.

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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7396-3:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 7396-3:2025) has been prepared by Technical Committee ISO/TC 121
"Anaesthetic and respiratory equipment " in collaboration with Technical Committee CEN/TC 215
“Respiratory and anaesthetic equipment” the secretariat of which is held by BSI.
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 January 2026, and conflicting national standards shall
be withdrawn at the latest by January 2026.
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.
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 7396-3:2025 has been approved by CEN as EN ISO 7396-3:2025 without any
modification.
International
Standard
ISO 7396-3
First edition
Medical gas pipeline systems —
2025-07
Part 3:
Proportioning units for the
production of synthetic medical air
Systèmes de distribution de gaz médicaux —
Partie 3: Unités mélangeurs pour la production d'air médical
reconstitué
Reference number
ISO 7396-3:2025(en) © ISO 2025

ISO 7396-3:2025(en)
© ISO 2025
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
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ISO copyright office
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 7396-3:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Nomenclature . 5
4.1 General .5
4.2 Components of a proportioning unit . .5
5 General requirements . 6
5.1 Safety.6
5.2 Usability .6
5.3 Materials .6
6 Design requirements . 7
6.1 Environmental conditions .7
6.2 Specification for synthetic medical air .7
6.3 Management of the conformity of supply .7
6.4 Sample port.8
6.5 Outlet connector .8
6.6 Inlet connectors: Pressure-equalizing system .8
6.6.1 Inlet connectors .8
6.6.2 Pressure-equalizing system.8
6.7 Requirements for outlet pressure .8
6.8 Indication of the functional parameters .9
6.9 Monitoring and alarm systems .9
6.10 Record capability . .9
6.11 Leakage .10
6.12 Manual shut-off valves .10
6.13 Automatic shut-off valves.10
6.14 Non-return valves .10
6.15 Pressure-relief valves .10
6.16 Mechanical strength .10
6.17 Filtration .11
6.18 Electromagnetic compatibility.11
6.19 Electrical safety .11
6.20 Oxygen analysers .11
6.21 Software . 12
6.22 Enclosure . 12
7 Constructional requirements .12
7.1 Cleanliness . 12
7.2 Lubricants . 12
8 Type test methods .12
8.1 General . 12
8.2 Test method for compliance of synthetic medical air to specification . 12
8.3 Test method for leakage . 12
8.4 Test method for alarms . 13
8.5 Test method for mechanical strength . 13
8.6 Test method for performance . . 13
8.7 Electromagnetic compatibility test . 13
8.8 Electrical safety test . 13
8.9 Test method for automatic shut-off valve . 13
8.10 Test for enclosure . 13

iii
ISO 7396-3:2025(en)
9 Marking and packaging . 14
9.1 Marking .14
9.2 Packaging .14
10 Information supplied by the manufacturer . 14
10.1 General .14
10.2 Information for installation .14
10.3 Instructions for use . 15
10.4 Information for maintenance . 15
Annex A (informative) Typical example of a proportioning unit with terminology .16
Annex B (informative) Typical forms for documenting compliance of the proportioning unit
with the requirements of this document . 17
Annex C (informative) Rationale .24
Annex D (informative) List of potential hazards .25
Bibliography .26

iv
ISO 7396-3:2025(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 121, Anaesthetic and respiratory equipment,
Subcommittee SC 6, Medical gas supply systems, in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 215, Respiratory and anaesthetic equipment, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
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.

v
ISO 7396-3:2025(en)
Introduction
Proportioning units are components of a supply system intended to supply synthetic medical air to a medical
gas pipeline distribution system complying with ISO 7396-1.
ISO 7396-1 requires that a supply system consists of at least three sources of supply which can typically be,
in addition to a proportioning unit, cylinder manifolds with associated pressure regulators.
The selection of the components to be associated to a proportioning unit within the supply system, included
the reservoir, is therefore the responsibility of the manufacturer of the pipeline system.
When a proportioning unit is used as primary source of supply, the other sources of supply are used as the
secondary and/or reserve source to supply the pipeline distribution system in the event of failure of the
proportioning unit.
This document pays particular attention to:
— use of suitable materials;
— safety (mechanical strength, leakage, safe relief of excess pressure);
— compliance of the product gas with specification;
— monitoring of the production process;
— cleanliness;
— testing;
— marking;
— packaging;
— information supplied by the manufacturer.
Annex C contains rationale statements for some of the requirements of this document.
NOTE Synthetic medical air is referred to as “air, synthetic medicinal” in the most current European
Pharmacopoeia monograph.
vi
International Standard ISO 7396-3:2025(en)
Medical gas pipeline systems —
Part 3:
Proportioning units for the production of synthetic medical air
1 Scope
1.1 This document specifies requirements relating to the construction and operation of devices producing air
through the blending of oxygen and nitrogen for use as sources of supply in supply systems for medical gases.
1.2 This document is applicable to proportioning units intended to produce synthetic medical air and air
for driving surgical tools by mixing in defined proportions oxygen and nitrogen.
1.3 This document is applicable to proportioning units intended to be components of a medical gas supply
system for medical air which supplies a medical gas pipeline distribution system complying with ISO 7396-1.
1.4 The number of proportioning units within the medical air supply system and their combination with
other sources of supply (e.g. cylinder manifolds) to ensure that the supply system consists of at least three
sources of supply is outside the scope of this document.
Requirements for the supply systems for medical air are given in ISO 7396-1.
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 4126-1, Safety devices for protection against excessive pressure — Part 1: Safety valves
ISO 7396-1, Medical gas pipeline systems — Part 1: Pipeline systems for compressed medical gases and vacuum
ISO 14971, Medical devices — Application of risk management to medical devices
ISO 15001, Anaesthetic and respiratory equipment — Compatibility with oxygen
ISO 20417, Information to be supplied by the manufacturer
IEC 60204-1, Safety of machinery - Electrical equipment of machines – Part 1: General requirements
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 61000-6-2, Electromagnetic compatibility (EMC) – Part 6-2: Generic standards - Immunity standard for
industrial environments
IEC 61000-6-4, Electromagnetic compatibility (EMC) – Part 6-4: Generic standards - Emission standard for
industrial environments
IEC 61439-1, Low-voltage switchgear and control gear assemblies - Part 1: General rules
IEC 62304, Medical device software — Software life cycle processes

ISO 7396-3:2025(en)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7396-1 and the following 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/
3.1
applicable policy
set of requirements relating to the medical device or accessory and its attributes such as form, fit, function,
process or information to be supplied by the manufacturer (3.7)
Note 1 to entry: The applicable policy shall be established by the authority having jurisdiction.
Note 2 to entry: The applicable policy may include specification for the format of the information to be supplied by the
manufacturer.
Note 3 to entry: Applicable policies can include regulations or guidelines and local laws.
3.2
air for driving surgical tools
natural or synthetic mixture of gases, mainly composed of oxygen (3.13) and nitrogen in specified
proportions, with defined limits for the concentration of contaminants, supplied by a medical gas pipeline
system (3.9) and intended for driving surgical tools
[SOURCE: ISO 7396-1:2016, 3.2, modified — Note to entry deleted.]
3.3
control system
device or set of devices to manage, command, direct or regulate the behaviour of other device(s) or system(s)
[SOURCE: ISO 7396-1:2016, 3.8]
3.4
double-stage pipeline distribution system
pipeline distribution system (3.14) in which gas is initially distributed from the supply system (3.26) at a
pressure higher than the nominal distribution pressure (3.10), and is then reduced to the nominal distribution
pressure by line pressure regulator(s) (3.6)
Note 1 to entry: This initial higher pressure is the nominal supply system pressure.
[SOURCE: ISO 7396-1:2016, 3.12]
3.5
information signal
signal that is not an alarm signal or a reminder signal
[SOURCE: ISO 7396-1:2016, 3.25]
3.6
line pressure regulator
pressure regulator (3.15) used in a double-stage pipeline distribution system (3.4) to reduce the nominal
supply system pressure to the nominal distribution pressure (3.10)
[SOURCE: ISO 7396-1:2016, 3.26]

ISO 7396-3:2025(en)
3.7
manufacturer
natural or legal person with responsibility for the design, manufacture, packaging and labelling of a device
before it is placed on the market under their own name, regardless of whether these operations are carried
out by that person themself or on their behalf by a third party
[SOURCE: ISO 7396-1:2016, 3.33, modified — Definition made gender neutral.]
3.8
medical air
natural or synthetic mixture of gases, mainly composed of oxygen (3.13) and nitrogen in specified
proportions, with defined limits for the concentration of contaminants, supplied by a medical gas pipeline
system (3.9) and intended for administration to patients
Note 1 to entry: Medical air may be produced by supply systems (3.26) with air compressors or by supply systems with
proportioning units (3.18). Medical air produced by air compressor systems is called “medicinal air”, and medical air
produced by proportioning systems is called “synthetic medicinal air” by the European Pharmacopoeia.
[SOURCE: ISO 7396-1:2016, 3.35]
3.9
medical gas pipeline system
complete system which comprises a supply system (3.26), a monitoring and alarm system and a distribution
system with terminal units at the points where medical gases or vacuum are required
[SOURCE: ISO 7396-1:2016, 3.36]
3.10
nominal distribution pressure
pressure which the medical gas pipeline system (3.9) is intended to deliver at the terminal units
[SOURCE: ISO 7396-1:2016, 3.38]
3.11
non-return valve
valve which permits flow in one direction only
[SOURCE: ISO 7396-1:2016, 3.41]
3.12
operating alarm
alarm to indicate to technical staff that it is necessary to replenish the gas supply or to correct a malfunction
[SOURCE: ISO 7396-1:2016, 3.42]
3.13
oxygen
gas for medicinal use where the oxygen concentration is at least the minimum specified in the relevant
pharmacopoeia monograph
[SOURCE: ISO 7396-1:2016, 3.45]
3.14
pipeline distribution system
portion of a medical gas or vacuum pipeline system linking the sources of supply of the supply system (3.26)
to the terminal units
[SOURCE: ISO 7396-1:2016, 3.48]

ISO 7396-3:2025(en)
3.15
pressure regulator
device which reduces the inlet pressure and maintains the set outlet pressure within specified limits
[SOURCE: ISO 7396-1:2016, 3.49]
3.16
pressure-relief valve
device intended to relieve excess pressure at a preset pressure
[SOURCE: ISO 7396-1:2016, 3.50]
3.17
primary source of supply
portion of the supply system (3.26) which supplies the pipeline distribution system (3.14)
[SOURCE: ISO 7396-1:2016, 3.51]
3.18
proportioning unit
device in which gases are mixed in a specified ratio
[SOURCE: ISO 7396-1:2016, 3.52]
3.19
reserve source of supply
that portion of the supply system (3.26) which supplies the complete, or portion(s) of the pipeline distribution
system (3.14) in the event of failure or exhaustion of both the primary and secondary sources of supply (3.22)
[SOURCE: ISO 7396-1:2016, 3.54]
3.20
reservoir
permanently installed container(s) designed for storing gas at pressures up to 3 000 kPa
[SOURCE: ISO 7396-1:2016, 3.56, modified — Note to entry deleted.]
3.21
safety
freedom from unacceptable risk
[SOURCE: ISO 7396-1:2016, 3.57]
3.22
secondary source of supply
portion of the supply system (3.26) which supplies the pipeline distribution system (3.14) in the event of
exhaustion or failure of the primary source of supply (3.17)
[SOURCE: ISO 7396-1:2016, 3.58]
3.23
shut-off valve
valve which prevents flow in both directions when closed
[SOURCE: ISO 7396-1:2016, 3.59]
3.24
single fault condition
condition in which a single means for protection against a safety hazard in equipment is defective or a single
external abnormal condition is present
Note 1 to entry: Planned maintenance of equipment is considered a normal condition.

ISO 7396-3:2025(en)
[SOURCE: ISO 7396-1:2016, 3.60]
3.25
source of supply
portion of the supply system (3.26) with associated control equipment which supplies the pipeline distribution
system (3.14)
[SOURCE: ISO 7396-1:2016, 3.62]
3.26
supply system
assembly which supplies the pipeline distribution system (3.14) and which includes all sources of supply
[SOURCE: ISO 7396-1:2016, 3.64]
4 Nomenclature
4.1 General
A typical example of a proportioning unit with the terminology used for its components is given in Annex A.
Typical forms for documenting compliance of the proportioning unit with the requirements of this document
are given in Annex B.
4.2 Components of a proportioning unit
A proportioning unit typically comprises of the following components:
a) inlet filters for oxygen and nitrogen;
b) non-return valves for oxygen and nitrogen;
c) automatic shut-off valves controlled by the inlet pressure of oxygen and nitrogen;
d) pressure regulators for oxygen and nitrogen;
e) shut-off valves and pressure-relief valve, as required;
f) a pressure-equalizing system;
g) a mixer connected to the oxygen and nitrogen sources of supply;
h) a control system with two independent oxygen analysers and two independent control panels;
i) a buffer reservoir;
j) a synthetic medical air reservoir fitted with a pressure-relief valve(s), a pressure gauge and a means of
purging;
k) an automatic shut-off valve, to prevent synthetic medical air out of specification being delivered by the
supply system to the pipeline distribution system.
NOTE The synthetic medical air reservoir is a mandatory component of the source of supply consisting of a
proportioning unit. However, for certification purposes (e.g. for the CE marking in the European Union) the synthetic
medical air reservoir cannot be always considered as part of the proportioning unit because the number of reservoirs,
their size, their characteristics and their interconnection will depend upon the design and the destination of use
of the pipeline distribution system to be supplied by a supply system with proportioning unit. These items are the
responsibility of the pipeline distribution system manufacturer. When the synthetic medical air reservoir is not
supplied as a component of the proportioning unit, the manufacturer, together with other information concerning
the installation of the proportioning unit, will recommend to the pipeline distribution system manufacturer the
characteristics and the minimum requirements to be met by the synthetic medical air reservoir.

ISO 7396-3:2025(en)
5 General requirements
5.1 Safety
Proportioning units shall, when transported, installed, commissioned, operated and maintained according
to the instructions of the manufacturer, present no risks with an unacceptable level in normal condition and
in single fault condition.
The risk management process in accordance with ISO 14971 should also consider the possibility of
undetected faults. Annex D provides a list of potential risks to consider.
In that case, a fault condition subsequently detected should be considered as a single fault condition. Specific
risk control measures to deal with such situations should be determined within the risk management
process.
NOTE 1 A situation in which a fault is not detected is considered a normal condition. Fault conditions/hazardous
situations can remain undetected over a period of time and as a consequence can lead to an unacceptable risk.
NOTE 2 Loss of mains electrical power or water supply is a single fault condition. A fault in control equipment is a
single fault condition.
Means shall be provided to connect both the normal and emergency utility supplies.
Check compliance by inspection of the risk management file.
Proportioning units should be designed and manufactured to:
a) minimize the risk arising from emitted electromagnetic fields which can disturb other equipment and
medical devices used within the healthcare facility;
b) have the appropriate level of electromagnetic immunity to operate safely within the electromagnetic
environment of healthcare facilities;
c) minimize electrical and mechanical hazards.
Evidence shall be provided by the manufacturer.
Applicable policies can apply. Where none exist, IEC 61000-6-1 can be used.
5.2 Usability
The foreseen risks related to use shall be addressed in a usability engineering process.
Check compliance by inspection of the usability engineering file.
NOTE For information related to usability, see, for example, IEC 62366-1 and IEC/TR 62366-2.
5.3 Materials
5.3.1 Materials which come in contact with the gases or their mixture, in normal condition and in single
fault condition, shall be resistant to corrosion and compatible with the gases or their mixture, whichever
they could come in contact with.
NOTE 1 See Annex C for rationale.
NOTE 2 Corrosion resistance includes resistance against the influence of moisture and the surrounding materials.
NOTE 3 Criteria for the selection of metallic and non-metallic materials are given in ISO 15001.

ISO 7396-3:2025(en)
NOTE 4 Compatibility with oxygen involves both combustibility and ease of ignition. Materials which burn in air
will burn violently in pure oxygen. Many materials which do not burn in air will do so in high concentrations of oxygen,
particularly under pressure. Similarly, materials which can be ignited in air require less energy to ignite in oxygen.
Less energy is required as the pressure increases. Many such materials can be ignited by friction at a valve seat or
by adiabatic compression produced when oxygen at high pressure is rapidly introduced into a system initially at low
pressure.
Check compliance by inspection of the list of materials which are in contact with the gases in normal
condition and in single fault condition and associated rationales for compatibility.
5.3.2 If lubricants are used, they shall be compatible with oxygen in normal condition and in single fault
condition.
Check compliance by inspection of the technical file.
6 Design requirements
6.1 Environmental conditions
Design specification shall be carried out after risk management procedure in accordance with ISO 14971.
The operation of proportioning units shall comply with the requirements of this document at temperatures
between +10 °C and +40 °C, as a minimum.
The environmental limits in which the proportioning unit may be operated shall be detailed in the
instructions for use.
Check compliance by inspection of the technical file.
6.2 Specification for synthetic medical air
Synthetic medical air produced by proportioning units shall comply with the following:
a) content: 95,0 % to 105,0 % of the nominal value which is between a volume fraction of 21,0 % to 22,5 %
of oxygen;
b) water vapour content ≤ 67 ml/m .
NOTE 1 Applicable policies applying to synthetic medical air produced by proportioning units can apply.
NOTE 2 See Annex C for rationale.
Check compliance by measurement in accordance with the test method given in 8.2.
Synthetic medical air can be used as air for driving surgical tools.
Oxygen and nitrogen shall comply with the specifications of the relevant pharmacopoeia monograph.
Other terms may be used by applicable policies.
6.3 Management of the conformity of supply
The specification for synthetic medical air given in 6.2 shall be met when the proportioning unit is delivering
up to the maximum flow specified by the manufacturer.
If the oxygen concentration of the mixture or the pressure supplied to the pipeline distribution system goes
out of specification, an emergency operating alarm shall be activated and the proportioning system shall
be automatically isolated by closing the shut-off valve fitted between the source of supply and the pipeline
distribution system. The system shall be arranged so that manual intervention is necessary to correct the
composition of the mixture before reconnecting the proportioning system to the pipeline system.

ISO 7396-3:2025(en)
Means shall be provided to purge the medical air reservoir.
Check compliance by functional tests.
6.4 Sample port
A sample port shall be fitted to enable the synthetic medical air to be tested.
Check compliance by visual inspection.
6.5 Outlet connector
The outlet connector of the proportioning unit shall be specified by the manufacturer, taking into account
the design flow.
A means of preventing any backflow (e.g. a check valve) should be fitted upstream of or integrated into the
connector.
Means shall be provided to allow the connection of the proportioning unit to the other components of the
supply system.
Check compliance by functional test.
6.6 Inlet connectors: Pressure-equalizing system
6.6.1 Inlet connectors
Means shall be provided to prevent the supply of nitrogen to the inlet connection for oxygen. Gas-specific
connectors may be used for this purpose.
Inlet should be fitted with a means of preventing any cross-contamination between the oxygen source and
the nitrogen source via the proportioning unit.
Check compliance by visual inspection.
6.6.2 Pressure-equalizing system
The oxygen and nitrogen inlet pressures to the proportioning unit shall be controlled by means of an
automatic pressure-equalizing system.
The pressure-equalizing system shall be designed to ensure that in case of a reduction in oxygen supply
pressure, the nitrogen supply pressure will be automatically reduced to a pressure level so that the oxygen/
nitrogen ratio in the gas mixture is maintained within the specified values.
Check compliance by functional test.
6.7 Requirements for outlet pressure
The pressure at the outlet port of the proportioning unit, measured at the flow specified by the manufacturer,
shall be not greater than 3 000 kPa in normal condition and in single fault condition.
NOTE See Annex C for rationale.
A double-stage pipeline distribution system can require an outlet pressure greater than 1 000 kPa.
Check compliance by measurement and functional tests.

ISO 7396-3:2025(en)
6.8 Indication of the functional parameters
Continuous online monitoring of oxygen concentration shall be provided to check the conformity of the
synthetic medical air to the specification.
Means shall be provided to allow the technical staff to visually control the conformity of the synthetic
medical air to specification.
Pressures and oxygen concentration shall be continuously displayed.
Check compliance by inspection of the technical file.
6.9 Monitoring and alarm systems
6.9.1 The control panels, the monitoring and the alarm system shall be designed in accordance with
ISO 7396-1.
For the purpose of this document, only operating alarms and information signals, as defined in ISO 7396-1,
are required.
NOTE See Annex C for rationale.
6.9.2 Sensors shall be provided to activate the following operating alarms:
— inlet pressures of oxygen and nitrogen out of specification;
— outlet pressure of synthetic medical air out of specification;
— oxygen concentration of synthetic medical air out of specification.
Check compliance by visual inspection and inspection of the technical file.
6.9.3 Sensors shall be prov
...