ISO 5145:2004

INTERNATIONAL ISO
STANDARD 5145
Second edition
2004-04-15


Cylinder valve outlets for gases and gas
mixtures — Selection and dimensioning
Raccords de sortie de robinets de bouteilles à gaz et mélanges de
gaz — Choix et dimensionnement





Reference number
ISO 5145:2004(E)
©
ISO 2004

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ISO 5145:2004(E)
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ii © ISO 2004 – All rights reserved

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ISO 5145:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Principle of the determination of valve outlets. 2
4 Determination of connection . 3
5 Allocation of connections . 5
6 Marking. 11
Annex A (normative) Gas groups . 12
Annex B (normative) Connections . 23
Annex C (normative) Use of connection nuts requiring tools. 28
Bibliography . 29

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ISO 5145:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5145 was prepared by Technical Committee ISO/TC 58, Gas cylinders, Subcommittee SC 2, Cylinder
fittings.
This second edition cancels and replaces the first edition (ISO 5145:1990), to which connections for 300 bar
and medical applications have been added.
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ISO 5145:2004(E)
Introduction
At the beginning of the 1960s the members of ISO/TC 58/SC 2 were charged with the task of drafting an
International Standard on gas cylinder valve outlets.
It soon became obvious that millions of different types of valve outlets are in use, and the various countries
concerned were not ready to give up their own systems. It was therefore only possible to draw up a list of the
existing provisions, either standardized or in use, which was published as Technical Report ISO/TR 7470. The
number and variety of such provisions give an idea of the complexity and scope of the task entrusted to
ISO/TC 58/SC 2.
Towards the end of the 1970s ISO/TC 58/SC 2 realized that the task in hand could only be achieved by
adopting a long-term solution; this was to create an ideal system of valve outlets which would not be
interchangeable with the existing systems. This system would be based on four fundamental criteria, namely
safety, simplicity, compactness and tightness.
Two key actions were then undertaken in parallel:
 a classification and grouping of gases and gas mixtures;
 a practical definition of an original, non-interchangeable, connection system.
ISO 5145 represents a synthesis of these two actions. It is a practical guide for the selection of cylinder valve
outlets for gases and gas mixtures. In view of the fact that no country seemed ready to give up their national
standards and to adopt an International Standard specifying the dimensions of gas cylinder valve outlets, it
was agreed that this International Standard need not be complied with where a national standard predates it.
ISO 5145 presents a logical system for determining valve outlets for gas cylinders for all gases or gas
mixtures. It is of special interest for those countries which have no national standards or regulations. Its
provisions can be called upon in the future in cases where a new gas or gas mixture is developed industrially.
The main purpose in standardizing valve outlets is to prevent the interconnection of non-compatible gases.
The user is cautioned to ensure that a particular outlet connection, when used, is compatible with any other
connections or gases that might be connected to that outlet. Because of the multiplicity of connections in use
and the existence of many national standards, this concern cannot be overstated.
ISO 5145 thus represents a basis for international agreement in the more or less remote future.

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INTERNATIONAL STANDARD ISO 5145:2004(E)

Cylinder valve outlets for gases and gas mixtures — Selection
and dimensioning
1 Scope
This International Standard establishes practical criteria for determining valve outlet connections for gas
cylinders.
It applies to the selection of gas cylinder valve outlet connections and specifies the dimensions for a number
of them.
This International Standard does not apply to connections used for cryogenic gas withdrawal or gases for
breathing equipment which are the subject of other International Standards.
WARNING — The gas cylinder valve outlet connection is not the only safeguard against accidental
misuse; gas cylinder labelling and colour code shall be checked before use.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 286-1:1988, ISO system of limits and fits — Part 1: Bases of tolerances, deviations and fits
ISO 286-2:1988, ISO system of limits and fits — Part 2: Tables of standard tolerance grades and limit
deviations for holes and shafts
ISO 10156:1996, Gases and gas mixtures — Determination of fire potential and oxidizing ability for the
selection of cylinder valve outlets
ISO 10286:1996, Gas cylinders — Terminology
ISO 10298:1995, Determination of toxicity of a gas or gas mixture
ISO 13338:1995, Determination of tissue corrosiveness of a gas or gas mixture
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ISO 5145:2004(E)
3 Principle of the determination of valve outlets
3.1 Basic principle
This International Standard establishes a method of allocating to any gas or mixture of gases contained in
cylinders, four-digit code numbers (FTSC). This code number categorizes the gas or gas mixture in terms of
its physical/chemical properties and/or inflammability, toxicity, state of the gas and corrosiveness (see A.1).
The FTSC code enables a gas or gas mixture to be assigned to one of the 15 “compatible” gas groups
(see A.2). Valve outlet connections are allocated to each group (see Clause 5).
NOTE Attention is drawn to the fact that the only purpose of the numerical code is to group compatible gases
together in order that the particular valve outlet assigned to each group may be selected. The code is only applicable for
the valve outlet selection used in this International Standard and is not intended as an identification code.
3.2 Single gases
Pure gases are assigned to one of the first fourteen-gas groups group, 15 being reserved for specific gas
mixtures. It is recognized that a “pure gas” may contain some impurities, but it is intended that this should not
affect the valve outlet selection.
Five groups are assigned to individual named gases from which mixtures and other gases are excluded.
These five groups are as follows:
a) group 2 – carbon dioxide;
b) group 5 – air;
c) group 10 – oxygen;
d) group 11 – nitrous oxide;
e) group 14 – acetylene.
3.3 Gas mixtures
3.3.1 Definition
For the purposes of this document, a gas mixture is defined as an intentional combination of two or more
gases which may be either in the gaseous phase or liquefied under pressure when in a gas cylinder.
NOTE This International Standard does not attempt to identify gas mixtures which may be safely and satisfactorily
prepared; this is the responsibility of the gas manufacturer. It does not describe any methods or techniques for preparing
gas mixtures.
3.3.2 Assignment of a gas mixture to a group
The principle of allocation of a four-digit numerical code (FTSC) to gas mixtures is the same as that for single
gases. The allocation of the FTSC code to a gas mixture, which allows the assignment of this mixture to one
of the group of gases and gas mixtures (see Table A.1), depends on the inflammability, oxidizing ability,
toxicity and corrosiveness of the final mixture. For the determination of flammability and oxidizing ability, use
ISO 10156, for toxicity use ISO 10298 and for corrosiveness use ISO 13338.
Mixtures containing spontaneously flammable gases (i.e. pyrophoric gases such as silane in Table A.10) shall
be considered as spontaneously flammable gas mixtures if the content of the pyrophoric gas(es) is more than
1,4 %.
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ISO 5145:2004(E)
4 Determination of connection
4.1 Connection
A connection is a mechanical device that conveys gas via a gas cylinder valve to a filling or use system
without leakage to the atmosphere. It shall be robust and able to withstand repeated connection and
disconnection. It shall be designed such that it can only be used for the group of gases to which it is allocated.
A connection comprises a minimum of three parts (see Figure 1):
a) a valve outlet — the part of the cylinder valve through which gas is discharged;
b) a connector — the part of the filling or use system through which the gas is conveyed;
c) a union nut — the means by which the connector is secured to the valve outlet and by which the seal is
ensured.
The design of the double-recess type of connection is derived from the “step index principle”.
The step index system comprises a double recess (faucet) into the valve outlet, into which a spigot of two
differing diameters is designed to fit (see the figure in Table 1). The lengths of the recesses and spigots are
the same for each connection but the diameters vary depending on the group of gases for which the recess or
spigot is designed. The form, dimensions and tolerances are illustrated in Table 1 which provides for 42 non-
interchangeable connections.
Three nominal diameters 24 mm, 27 mm and 30 mm have been adopted for the connections (see Annexes B
and C). The thread is a Whitworth thread with a pitch of 2 mm (see Figure 2).
NOTE Internal “double-recess step index connections” are not used because of their excessive size.
4.2 Leak tightness
Leak tightness is achieved by the sealing end of the connector bearing on the conical part of the valve outlet
connection, this seal being maintained by the union nut (see Annex B).
Other methods of sealing may be adopted.
No details of the external dimensions of the union nut are given since this will be subject to the method
adopted for applying the sealing force (i.e. with a spanner or by hand).
This International Standard does not specify the choice of materials; however, it is necessary to use materials
for the O-ring, valve and valve connector that are compatible with the gas content of the cylinder and the
service for which they are intended.
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ISO 5145:2004(E)
Table 1 — Non-interchangeable combinations A + B
Dimensions in millimetres

Female Male
Nominal Constant A + B
Available combinations
diameter
28 32 36
of the
connec-
tion =
Total of
Right-
nominal
Left-hand right- and
A B A B A B hand
thread
thread left-hand
thread
diameter
threads
D, d
11,2 16,8
11,9 16,1
24 12,6 15,4 — — — — 5 5 10
13,3 14,7
14 14
11,8 20,2
12,5 19,5
13,2 18,8
27 — — 13,9 18,1 — — 7 7 14
14,6 17,4
15,3 16,7
16 16
12,4 23,6
13,1 22,9
13,8 22,2
14,5 21,5
30 — — — — 15,2 20,8 9 9 18
15,9 20,1
16,6 19,4
17,3 18,7
18 18
Total numbers of combinations 21 21 42
NOTE For the tolerances, see ISO 286-1 and ISO 286-2.

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ISO 5145:2004(E)

Key
1 valve
2 connector
3 union nut
a
Thread according to Figure 2b).
b
Thread according to Figure 2a).
Figure 1 — Female and male connections
5 Allocation of connections
The allocation of 33 connections from the 42 that are available is shown in Table 2. Table 3 shows that each
group of gases has been established in accordance with:
a) the FTSC code;
b) the gases for other groups which may be component parts of the mixture of which the final properties are
similar to those of that group;
c) the connection(s) which is (are) allocated to the group.
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ISO 5145:2004(E)
Dimensions in millimetres

a) Internal thread

b) External thread
Nominal diameter = major diameter D, d 24 27 30
Pitch diameter D , d 22,72 25,72 28,72
2 2
Minor diameter D , d 21,44 24,44 27,44
1 1
Figure 2 — Basic dimensions of Whitworth threads with pitch P equal to 2 mm

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ISO 5145:2004(E)
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Table 2 — Allocation of valve outlets for gases and gas mixtures by connection type
Nominal diameter of the connection
24 27 30
A-B A-B A-B
Left-hand thread Right-hand thread Left-hand thread Right-hand thread Left-hand thread Right-hand thread
combination combination combination
Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas
(utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture (FTSC
(FTSC code) (FTSC code) code)
tion) (FTSC code) tion) tion) (FTSC code) tion) tion) (FTSC code) tion)
mm   mm   mm
a
11,2-16,8 Medical 3 (M) Helium and 11,8-20,2  3 (M) Nitrogen 12,4-23,6  3 (M) Helium-oxygen
8 (M)
cyclopropane xenon (0110) mixture (O < 20%)

2

(2200)
6 1 18 11 34 25
11,9-16,1  10 (I) Oxygen 12,5-19,5  15 (M) Air + He + CO 13,1-22,9  15 (M) O + N
2 2

(O > 22%)
(4150) (CO < 1%)
2

Mixture or O + He
2
(4203; 4300;
4301; 4303;
4330; 4343;
4351)
b
7 2 19 12 35 26
12,6-15,4  15 (M) Medical air 13,2-18,8  15 (M) 50 % O - 13,8-22,2  15 (M) O - CO
2 2 2

and synthetic 50 % N O mixture
2

medicinal air mixture (CO u 7%)
2
 3 13 27
8 20 36
13,3-14,7 6 (2150) 3 (I) (M) (0150) 13,9-18,1 13 (I) (5100; 5200; 5 (I) Air 14,5-21,5  15 (M) O - CO mixture
2 2

a
5300; 5301; (CO > 7%)
(I) 2
Inert gas and (1050)
5350)
gas mixtures
(0150)
9 4 21 14 37 28
14-14 6 Hydrogen 10 (M) Oxygen 14,6-17,4 9 (I) (3300; 3310; 4 (I) (0200; 0201; 15,2-20,8 6 (I) (2170) 3 (M) N + NO mixture
2

(100 < NO
(2150) (4050) 3150) 0203; 0213;
(I)
0300; 0303; < 1 000 ppm)
0253)
10 5 22 15 38 29

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ISO 5145:2004(E)
8 © ISO 2004 – All rights reserved
Table 2 — (continued)
Nominal diameter of the connection
30
24 27
A-B A-B A-B
Left-hand thread Right-hand thread Left-hand thread Right-hand thread Left-hand thread Right-hand thread
combination combination combination
Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas Group Gas or gas
(utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture (utilisa- mixture
(FTSC code) (FTSC code) (FTSC code)
tion) (FTSC code) tion) tion) (FTSC code) tion) tion) (FTSC code) tion)
mm   mm   mm
(2200; 2201;
Nitrous oxide
15,3-16,7 8 (I) (2250) 11 (M) 15,9-20,1 8 (I) 2203; 2300; 3 (I) (0170)
(4110)
2301)
23 16 39 30
Commercial
Carbon
butane and Air
16-16 6 (I) 2 (M) dioxide 16,6-19,4 7 (I) (0202; 2202) 5 (I)
propane (1070)
(0110)
(2100)
24 17 40 31

(2100; 2110)
(except H
2
17,3-18,7 6 (I) 10 (I) (4070)
and butane
and propane)

41 32
Acetylene 3 (M) SF , C F , C F
6 2 6 3 8
18-18 14 (I)
(5130) 1 (I)
(0100)
42 33
a I for industrial applications; M for medical applications.
b
Caution: this valve outlet is used for two different applications (oxidizing, toxic and/or corrosive gases and medicinal breathable application). However, these applications are so different that this is found acceptable
(toxic gas is unlikely to be distributed in a hospital).

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ISO 5145:2004(E)
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Table 3 — Allocation of valve outlets by gas group
Allocation of outlet connections
Nominal diameter of the connection
Right-
Group Gas and gas mixture
Single gases, hand (RH) 24 27 30
No. characteristic at 15°C FTSC code, or left-
Gases and gas A-B, Gases and gas A-B, Gases and gas A-B,
code FTSC hand (LH)
mixtures and/or combination mixtures and/or combination mixtures and/or FTSC combination
thread
FTSC code FTSC code code
mm mm mm
1 Non-flammable, non-toxic 0100 RH   0100 18-18
gases; less stable
thermally than group 3
     33
2 Carbon dioxide 0110 RH  0110 16-16 (M)
    17
3 Non-flammable, non-toxic 0150 RH Medical helium 11,2-16,8 Nitrogen (M) (I) 11,8-20,2 He-O (O <20%) 12,4-23,6
2 2
and thermally stable gases xenon
0170
(except carbon dioxide)
1 25
Inert gas and gas 13,3-14,7 0170 15,9-20,1
mixtures
15,2-20,8
N + NO mixture
2

(100 < NO < 1 000 ppm)
29
SF , C F , C F 18-18
6 2 6 3 8
   4 11 33
4 Non-flammable, toxic and 0200; 0201; RH  0200; 0201; 0213; 14,6-17,4
corrosive by hydrolysis 0203; 0213; 0300; 0303; 0253;
gases 0300; 0303; 0263
0253; 0263
    15
a
5 1150 RH  1050 13,9-18,1 1170 16,6-19,4
Air only
1170 Air (I) Air (I)
    14 31
6 Flammable and non-toxic 2100; 2110; LH H 14-14 Commercial butane 16-16 2170 15,2-20,8
2
2120; 2150;
gases and propane
u 250 bar
2170
10 38
2150 13,3-14,7 2100; 2110 except H 17,3-18,7
2
and commercial butane
and propane
   9 24 41
7 Flammable and corrosive 0102; 2102 LH   0102; 2102 16,6-19,4
(basic gases)
8 Flammable, toxic and 2200 LH Medical 11,2-16,8 2250 15,3-16,7 2200; 2201; 2203; 2300; 15,9-20,1
corrosive (acidic) cyclopropane 2301
or non-corrosive gases
   6 23 39

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ISO 5145:2004(E)
10 © ISO 2004 – All rights reserved
Table 3 — (continued)
Allocation of outlet connections
Nominal diameter of the connection
Right-
Group Gas and gas mixture 30
Single gases, hand (RH) 24 27
No. characteristic at 15°C FTSC code, or left-
Gases and gas A-B, Gases and gas A-B, Gases and gas A-B,
code FTSC hand (LH)
mixtures and/or combination mixtures and/or combination mixtures and/or FTSC combination
thread FTSC code FTSC code code
mm mm mm
9 Spontaneously 3150; 3300; LH  3150; 3300; 3310 14,6-17,4
flammable 3310
    22
10 Oxygen and high pressure 4050 RH 4050 (M) 14-14  4070 including high 17,3-18,7
oxidant oxygen (M) pressure oxidant
4070
5
4050 (I) 11,9-16,1
   2  32
11 Nitrous oxide 4110 RH  4110 (M) 15,3-16,7
    16
12 Oxidant, toxic and 4203; 4300; RH  4203; 4300; 4301; 12,5-19,5
corrosive gases 4301; 4303; 4303; 4330; 4343;
4330; 4343; 4351
4351; 4361
b

12
13 Flammable gases subject 5100; 5200; LH  5100; 5200; 5300; 13,9-18,1
to decomposition or 5300; 5301;
5301; 5350
polymerization 5350
    21
14 Acetylene only 5130 LH   5130 (Acétylène) 18-18
     42
15 Oxidant, non-toxic and RH Medicinal air and 12,6-15,4 50 % N O- 50 % O 13,2-18,8 O + N ou O −He 13,1-22,9
2 2 2 2 2
synthetic medicinal
non-corrosive gas mixture
mixture (M) mixtures
26
air (M)
O -CO (CO u 7 %) (M) 13,8-22,2
2 2 2

13 27
air+He+CO 12,5-19,5 CO -O (CO > 7 %) (M) 14,5-21,5
2 2 2

(CO < 1 %)
mixture (M)
b
   3  28
12
a
For medical application, see group 15.
b
Caution: this valve outlet is used for two different applications (oxidizing, toxic and/or corrosive gases and medicinal breathable applications). However, these applications are so different that this is found acceptable
(toxic gas is unlikely to be distributed in a hospital).

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ISO 5145:2004(E)
6 Marking
The outlets and the connections shall be marked with the number of the corresponding outlet as indicated in
Table 4.
Table 4 — Marking
Mark number
DN A B
Left hand Right hand
thread thread
11,2 16,8 6 1
11,9 16,1 7 2
24
12,6 15,4 8 3
13,3 14,7 9 4
14 14 10 5
11,8 20,2 18 11
12,5 19,5 19 12
13,2 18,8 20 13
27 13,9 18,1 21 14
14,6 17,4 22 15
15,3 16,7 23 16
16 16 24 17
12,4 23,6 34 25
13,1 22,9 35 26
13,8 22,2 36 27
14,5 21,5 37 28
30
15,2 20,8 38 29
15,9 20,1 39 30
16,6 19,4 40 31
17,3 18,7 41 32
18 18 42 33

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ISO 5145:2004(E)
Annex A
(normative)

Gas groups
A.1 Numerical gas code (FTSC)
A.1.1 General
The code number assigned to each gas is based on the following four physico-chemical criteria.
Category I: fire potential, defining the gas behaviour with respect to combustion.
Category II: toxicity.
Category III: gas state, defining the physical state of the fluid in the cylinder at 15 °C within a given pressure
range.
Category IV: corrosiveness (with respect to living tissue).
Each category is subdivided into different characteristics, each identified by a different digit. In this way, a gas
in a given state is characterized by a series of four digits (one digit per category) as illustrated below.
A.1.2 Fire potential, category I
Subdivision 0: inert (any gas not classified under subdivisions 1 to 5 below);
Subdivision 1: supports combustion (oxidizing gas having an oxipotential equal to or less than that of air);
Subdivision 2: flammable (gas having flammable limits in air);
Subdivision 3: spontaneously flammable;
Subdivision 4: highly oxidizing (oxidizing gas having an oxipotential greater than that of air);
Subdivision 5: flammable and subject to decomposition or polymerization.
A.1.3 Toxicity, category II
Subdivision 0: life supporting at atmospheric pressure;
Subdivision 1: non-toxic LC50 > 0,005 % by volume; (For LC50, see the definition in ISO 10298.)
Subdivision 2: toxic; 0,000 2 % by volume < LC50 u 0,005 % by volume;
Subdivision 3: very toxic LC50 u 0,000 2 % by volume.
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ISO 5145:2004(E)
A.1.4 State of the gas (in the cylinder at 15 °C, category III)
Subdivision 0: liquefied gas at 35 bar or less;
Subdivision 1: liquefied gas at over 35 bar;
Subdivision 2: liquid withdrawal – liquefied gas (optional);
Subdivision 3: dissolved gas;
Subdivision 4: gas phase withdrawal at 35 bar or less;
Subdivision 5: compressed gas between 35 bar and 250 bar (Europe);
Subdivision 6: compressed gas between 35 bar and 182 bar (North America);
Subdivision 7: compressed gas above 182 bar (North America) or 250 bar (Europe).
Either subdivision 5 or subdivision 6 shall be used, never both. The selection of either subdivision will
determine the meaning of subdivision 7.
Subdivisions 5 and 6 have been adopted as a result of a compromise between the European and the North
American proposals. The European preference for a limit of 250 bar reflects the current tendency towards
higher-pressure applications. The current North American practice requires a limit of 182 bar for which their
pressure reducing valves are designed. This is the working pressure at the referenced temperature of 15 °C.
Therefore three pressure classes have been retained:
Subdivision 4: 35 bar or less — gas only (including cryogenic gas withdrawal);
Subdivision 5 or 6: medium pressure range, each user being imperatively required to select one subdivision
exclusively to determine the upper limit of the medium pressure range (i.e. 182 bar or 250 bar);
Subdivision 7: high pressure range, the lower limit (182 bar or 250 bar) of which depends on the subdivision
selected for the medium pressure range.
A number of pressure ranges have been established to safeguard the selection of the proper cylinder valve
outlet connection. These ranges have been chosen to protect downstream regulators and other ancillary
equipment from over-pressurized conditions.
Subdivisions 8 and 9 have been allocated for liquid withdrawal cylinders of cryogenic gases in the USA.
All pressures are working pressures in accordance with ISO 10286.
A.1.5 Corrosiveness, category IV
Subdivision 0: non-corrosive;
Subdivision 1: non-halogen acid forming;
Subdivision 2: basic;
Subdivision 3: halogen acid forming.

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ISO 5145:2004(E)
A.2 Grouping of gases
A.2.1 General
The characteristics of each gas group are summarized in Table A.1.
Table A.1 — Gas group characteristics
Group Characteristics
1 Non-flammable, non-toxic gases and qualifying gas mixtures, less stable thermally than group 3
2 Carbon dioxide
3 Non-flammable, non-toxic and thermally stable gases (except carbon dioxide) and qualifying gas mixtures
4 Non-flammable, toxic and corrosive (or corrosive by hydrolysis) gases and qualifying gas mixtures
5 Air
6 Flammable and non-toxic gases and qualifying gas mixtures
7 Flammable, toxic and corrosive (basic) gases and qualifying gas mixtures
8 Flammable, toxic and corrosive (acidic) or non-corrosive gases and qualifying gas mixtures
9 Spontaneously flammable gases and qualifying gas mixtures
10 Oxygen and high pressure oxidant
11 Nitrous oxide
12 Oxidant, toxic and/or corrosive gases and qualifying gas mixtures
13 Flammable gases and qualifying gas mixtures subject to decomposition or polymerization
14 Acetylene
15 Oxidant, non-toxic and non-corrosive gas mixtures (normally medical)
Summaries of the gases and gas mixtures belonging to each group are given in A.2.2 to A.2.16.
NOTE For compressed gases given in the following tables (Tables A.2 to A.15), the third digit used in this document
is a 5. Most of these gases may be filled in a gas cylinder at a different pressure and consequently the digits 6 or 7 are
then to be used. For liquefied gases, the third
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