ISO 5149-1:2026

International
Standard
ISO 5149-1
Second edition
Refrigerating systems and heat
2026-11
pumps — Safety and environmental
requirements —
Part 1:
Vocabulary
Systèmes frigorifiques et pompes à chaleur — Exigences de
sécurité et d'environnement —
Partie 1: Vocabulaire
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions .1
3.1.1 Terms related to refrigerating systems .1
3.1.2 Terms related to locations .2
3.1.3 Terms related to pressure .3
3.1.4 Terms related to components of refrigerating systems .3
3.1.5 Terms related to piping, joint and fitting .5
3.1.6 Terms related to safety devices .6
3.1.7 Terms related to fluids, substances and safety characteristics .7
3.1.8 Terms related to refrigerant disposal .9
3.1.9 Terms related to airflow .9
3.1.10 Miscellaneous terms .9
3.2 Abbreviated terms .10
Bibliography .11
Index .12

iii
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)
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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 86, Refrigeration and air-conditioning,
Subcommittee SC 1, Safety and environmental requirements for refrigerating systems.
This second edition cancels and replaces the first edition (ISO 5149-1:2014), which has been technically
revised. It also incorporates the Amendments ISO 5149-1:2014/Amd 1:2015 and ISO 5149-1:2014/Amd
2:2021.
The main changes are as follows:
— the entire technical content has been moved to ISO 5149-3, keeping only the vocabulary in this document.
A list of all parts in the ISO 5149 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
Introduction
This document defines terms for the ISO 5149 series, the purpose of which is to specify requirements for
the safety of persons and property involved with refrigerating systems, heat pumps and the recovery of
refrigerants. The ISO 5149 series also provides guidance for the protection of the environment. The series
establishes procedures for the following items as regards refrigerating systems, heat pumps and the
recovery of refrigerants:
— design;
— construction;
— testing;
— marking and documentation;
— installation;
— operation;
— maintenance;
— repair;
— refrigerating system disposal.
The ISO 5149 series is applicable to:
a) refrigerating systems, stationary or mobile, of all sizes, except vehicle air conditioning systems covered
by a specific product standard, e.g. ISO 13043 and SAE J 639;
b) secondary cooling or heating systems;
c) the location of the refrigerating systems;
d) parts replaced and components added if they are not identical in function and capacity.

v
International Standard ISO 5149-1:2026(en)
Refrigerating systems and heat pumps — Safety and
environmental requirements —
Part 1:
Vocabulary
1 Scope
This document defines terms used in the specification, design, manufacture, construction, installation,
commissioning, maintenance and decommissioning of refrigerating systems with regard to safety and
environmental requirements.
The term "refrigerating systems" includes heat pumps and air conditioners.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
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 Terms and definitions
3.1.1 Terms related to refrigerating systems
3.1.1.1
sorption system
refrigerating system in which refrigeration is achieved by evaporation of a refrigerant, the vapour then being
absorbed or adsorbed by an absorbent or adsorbent medium respectively, from which it is subsequently
expelled at a higher partial vapour pressure by heating and then liquefied by cooling
Note 1 to entry: Absorption systems and adsorption systems are covered in this definition.
3.1.1.2
cascade system
two or more independent refrigerant circuits where the condenser of one system rejects heat directly to the
evaporator of another
3.1.1.3
indirect system
system with more than one degree of separation from the occupied space
3.1.1.4
limit-charged system
refrigerating system in which the internal volume and total refrigerant charge are such that, with the system
idle, the allowable pressure will not be exceeded if complete evaporation of the refrigerant charge occurs

3.1.1.5
high-pressure side
part of a refrigerating system operating approximately at the condenser pressure
3.1.1.6
low-pressure side
part of a refrigerating system operating approximately at the evaporator pressure
3.1.1.7
refrigerating system
combination of interconnected refrigerant-containing parts constituting one closed circuit in which the
refrigerant is circulated for the purpose of extracting and rejecting heat (i.e. cooling and heating)
Note 1 to entry: "Refrigerating system" includes heat pumps and air conditioners.
3.1.1.8
self-contained system
complete factory-made refrigerating system in a suitable frame or enclosure, which is fabricated and
transported as a complete unit system, or in two or more sections and in which no refrigerant-containing
parts are connected on site other than by isolation valves, such as companion (block) valves
3.1.1.9
hermetically sealed system
refrigerating system in which all refrigerant containing parts are made tight by welding, brazing or a similar
permanent connection, which may include capped valves and capped service ports that allow proper repair
or disposal and which have a tested leakage rate of less than 3 g per year under a pressure of at least a
quarter of the maximum allowable pressure
Note 1 to entry: Permanent mechanical joints meeting the requirements of hermetically sealed joints in ISO 14903 are
considered to be similar permanent connections.
3.1.1.10
unit system
self-contained system that is assembled, filled, ready for use and tested prior to its installation and is
installed without the need for connecting any refrigerant-containing parts
3.1.1.11
split system
refrigerating system, comprising one or more factory-made indoor units in a space and one or more factory-
made units which are located outside the space and which are connected on site by refrigerant piping to
form a single functional system
3.1.1.12
multi-split system
split system with at least two indoor units
3.1.2 Terms related to locations
3.1.2.1
crawl space
space that is generally accessed for maintenance only and where it is not possible to walk or access by
walking
Note 1 to entry: The height of crawl spaces is usually less than 1 m.
3.1.2.2
exit passageway
passageway in the immediate vicinity of the exit through which people may leave the building

3.1.2.3
hallway
corridor for the passage of people
3.1.2.4
machinery room
enclosed room or space, with mechanical ventilation, sealed from public areas and not accessible to the
public, which is intended to contain components of the refrigerating system
Note 1 to entry: A machinery room can contain other equipment provided that the design and its installation
requirements are compatible with the requirements for the safety of the refrigerating system.
3.1.2.5
occupied space
space in a building which is bounded by walls, floors and ceilings and which is used and intended for human
occupation or human activities or both
3.1.2.6
open air
unenclosed space, possibly but not necessarily roofed
3.1.2.7
separate refrigeration machinery room
machinery room intended to contain only components of the refrigerating system, accessible only to
competent personnel for the purposes of inspection, maintenance and repair
Note 1 to entry: The term "machinery room" includes separate refrigeration machinery rooms.
3.1.2.8
class IV ventilated enclosure
enclosure containing the refrigerating system that does not enable air to flow from the enclosure to the
surrounding space and has a ventilation system that produces airflow from the enclosure to the open air or
to a suitable indoor space through a ventilation duct
3.1.3 Terms related to pressure
3.1.3.1
design pressure
pressure chosen for the strength calculation of each component
Note 1 to entry: The design pressure is used for determining the necessary materials, thickness and construction for
components with regard to their ability to withstand pressure.
3.1.3.2
maximum allowable pressure
PS
P
S
maximum pressure for which a system or component is designed, as specified by the manufacturer
3.1.3.3
strength test pressure
pressure that is applied to test the strength of a refrigerating system or any part of it
3.1.4 Terms related to components of refrigerating systems
3.1.4.1
coil
part of the refrigerating system constructed from pipes or tubes suitably connected and serving as a heat
exchanger (evaporator or condenser)
Note 1 to entry: A header connecting the tubes of the heat exchanger is part of the coil.

3.1.4
...