ISO/TS 16922

Natural gas — Odorization

This document gives the specifications and guidelines for the methods to be used in the odorization of natural gas and other methane rich gases delivered through natural gas networks to gas applications under a safety point of view. This document also specifies the principles for the odorization technique (including handling and storage of odorants) and the control of odorization of natural gas and other methane rich gases.

Gaz naturel — Odorisation

General Information

• Status: Not Published
• ICS: 75.060 - Natural gas
• Technical Committee: ISO/TC 193 - Natural gas
• Drafting Committee: ISO/TC 193 - Natural gas
• Current Stage: 6000 - International Standard under publication
• Completion Date: 30-Aug-2022

RELATIONS

• Revises: ISO/TR 16922:2013 - Natural gas — Odorization
• Effective Date: 06-Jun-2022

Standards Content (sample)

ISO/TC193/WG5
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ISO/DTSPRF TS 16922:2022(E)
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ISO TC 193/WG 5
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Date: 2022-07-27xx
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Secretariat: NEN
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Natural gas — Odorization
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Gaz naturel — Odorisation
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ISO/DTSPRF TS 16922:2022(E)
© ISO 2022
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part

of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or

mechanical, including photocopying, or posting on the internet or an intranet, without prior written

permission. Permission can be requested from either ISO at the address below or ISO’s member body

in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2022 – All rights reserved
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ISO/DTS PRF TS 16922:2022(E)
Contents

Foreword ............................................................................................................................................................ iv

Introduction ....................................................................................................................................................... v

1 Scope ....................................................................................................................................................... 1

2 Normative references ....................................................................................................................... 1

3 Terms and definitions ....................................................................................................................... 1

4 General requirements ....................................................................................................................... 2

4.1 Necessary odorant addition ............................................................................................................ 2

4.2 Requirements and parameters for consideration when selecting an odorant .............. 2

4.3 Public awareness ................................................................................................................................ 3

5 General remarks on odorant behaviour ..................................................................................... 3

5.1 Masking and fading of odorants .................................................................................................... 3

5.2 Seals and membranes ....................................................................................................................... 3

5.3 Pipelines ................................................................................................................................................ 3

5.4 Buried pipeline.................................................................................................................................... 4

6 Safety precautions .............................................................................................................................. 4

6.1 Handling of odorants ......................................................................................................................... 4

6.2 Spill management and remediation ............................................................................................. 4

6.3 Transportation and storage ............................................................................................................ 5

7 Odorization technique ...................................................................................................................... 5

7.1 Odorization of pipeline networks ................................................................................................. 5

7.1.1 Odorization of transmission pipelines ........................................................................................ 5

7.1.2 Odorization of distribution pipelines .......................................................................................... 6

7.1.3 Combined odorization of transmission and distribution pipelines ................................... 6

7.2 Odorizer ................................................................................................................................................. 6

7.2.1 General ................................................................................................................................................... 6

7.2.2 Liquid injection odorizers ............................................................................................................... 6

7.2.3 Positioning of odorant injectors .................................................................................................... 7

7.2.4 Evaporation odorizers ...................................................................................................................... 8

7.3 Design of installation......................................................................................................................... 9

7.3.1 Odorization rooms ............................................................................................................................. 9

7.3.2 Ventilation ............................................................................................................................................ 9

7.3.3 Installation of injection point and injection pipe ..................................................................... 9

7.3.4 Tank design and operations............................................................................................................ 9

7.3.5 Spill kit ................................................................................................................................................ 10

7.4 Pressure resistance ........................................................................................................................ 10

7.5 Addition of odorant ........................................................................................................................ 10

7.5.1 Control of the addition ................................................................................................................... 10

7.5.2 Monitoring and control devices .................................................................................................. 10

7.5.3 Testing and commissioning ......................................................................................................... 10

8 Control of odorization .................................................................................................................... 11

8.1 General ................................................................................................................................................ 11

8.2 Check of odorization equipment and systems ....................................................................... 11

8.3 Control of odorization of the gas ................................................................................................ 11

8.4 Odor complaints .............................................................................................................................. 11

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ISO/DTSPRF TS 16922:2022(E)

Bibliography .................................................................................................................................................... 12

Foreword ........................................................................................................................................................... iv

Introduction ....................................................................................................................................................... v

1 Scope ....................................................................................................................................................... 1

2 Normative references ........................................................................................................................ 1

3 Terms and definitions ....................................................................................................................... 1

4 General requirements ....................................................................................................................... 2

4.1 Necessary odorant addition ............................................................................................................ 2

4.2 Requirements and parameters for consideration when selecting an odorant ............... 2

4.3 Public awareness ................................................................................................................................ 3

5 General remarks on odorant behaviour ..................................................................................... 3

5.1 Masking and fading of odorants ..................................................................................................... 3

5.2 Seals and membranes ........................................................................................................................ 3

5.3 Pipelines ................................................................................................................................................ 3

5.4 Buried pipeline .................................................................................................................................... 4

6 Safety precautions .............................................................................................................................. 4

6.1 Handling of odorants ......................................................................................................................... 4

6.2 Spill management and remediation ............................................................................................. 4

6.3 Transportation and storage ............................................................................................................ 5

7 Odorization technique ...................................................................................................................... 5

7.1 Odorization of pipeline networks ................................................................................................. 5

7.1.1 Odorization of transmission pipelines ........................................................................................ 5

7.1.2 Odorization of distribution pipelines .......................................................................................... 6

7.1.3 Combined odorization of transmission and distribution pipelines ................................... 6

7.2 Odorizer ................................................................................................................................................. 6

7.2.1 General ................................................................................................................................................... 6

7.2.2 Liquid injection odorizers ............................................................................................................... 6

7.2.3 Positioning of odorant injectors .................................................................................................... 7

7.2.4 Evaporation odorizers ...................................................................................................................... 8

7.3 Design of installation ......................................................................................................................... 9

7.3.1 Odorization rooms ............................................................................................................................. 9

7.3.2 Ventilation ............................................................................................................................................ 9

7.3.3 Installation of injection point and injection pipe ..................................................................... 9

7.3.4 Tank design and operations ............................................................................................................ 9

7.3.5 Spill kit ................................................................................................................................................ 10

7.4 Pressure resistance ......................................................................................................................... 10

7.5 Addition of odorant ......................................................................................................................... 10

7.5.1 Control of the addition ................................................................................................................... 10

7.5.2 Monitoring and control devices .................................................................................................. 10

7.5.3 Testing and commissioning .......................................................................................................... 10

8 Control of odorization .................................................................................................................... 11

8.1 General ................................................................................................................................................ 11

8.2 Check of odorization equipment and systems........................................................................ 11

8.3 Control of odorization of the gas ................................................................................................ 11

8.4 Odour complaints ............................................................................................................................ 11

Bibliography .................................................................................................................................................... 12

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ISO/DTS PRF TS 16922:2022(E)
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ISO/DTSPRF TS 16922:2022(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.

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 documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directiveswww.iso.org/directives).

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. Details of any

patent rights identified during the development of the document will be in the Introduction and/or on

the ISO list of patent declarations received (see www.iso.org/patentswww.iso.org/patents).

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

Formatted: Font: Italic

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

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www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
Formatted: Pattern: Clear
Formatted: Pattern: Clear
This document was prepared by Technical Committee ISO/TC 193, Natural Gasgas.
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This secondfirst edition ISO/TS 16922 cancels and replaces the first edition (ISO/TR 16922:2013),

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which has been technically revised.
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The main changes compared to the previous edition are as follows:
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— modification of the structure of the technical report :Technical Report, new clauses :: 4.1 Necessary

odorant addition, 4.2 Requirements and parameters for consideration when selecting an odorant, 4.3

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Public awareness, 5.1 Masking and fading of odorants, , Clause 7 Odorization technique, 7.1

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Odorization of pipeline networks, 7.1.1 Odorization of transmission pipelines, 7.1.2 Odorization of

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distribution pipelines, 7.1.3 Combined odorization of transmission and distribution pipelines, 7.3

Design of installation, 7.3.1 Odorization rooms, 7.3.2 Ventilation, 7.3.3 Installation of injection point

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and injection pipe, 7.3.4 Tank design and operations, 7.3.5 Spill kit.;
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— modification of clause 7.2 Odorizer. Formatted: Pattern: Clear
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Any feedback or questions on this document should be directed to the user’s national standards body. A

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complete listing of these bodies can be found at
www.iso.org/members.htmlwww.iso.org/members.html. Formatted: Pattern: Clear
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ISO/DTS PRF TS 16922:2022(E)
Introduction

Processed natural gas normally has little or no odorodour. For safety reasons distributed natural gas is

therefore be odorized, to permit the detection of the gas by smell.

The odorization is predominantly a safety measure for the user of natural gas. Odorized natural gas needs

to be recognized by the characteristic smell.

This technical reportdocument may also be applied to other gases used in gas supply as e.g. biomethane,

blends containing hydrogen, regasified LNG or LBG, LPG for conditioning in gas supply, etc.

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TECHNICAL SPECIFICATION ISO/DTS PRF TS 16922:2022(E)
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Natural gas - Odorization
1 Scope

This Technical Specificationdocument gives the specifications and guidelines for the methods to be used

in the odorization of natural gas and other methane rich gases delivered through natural gas networks to

gas applications under a safety point of view.

This Technical Specificationdocument also specifies the principles for the odorization technique

(including handling and storage of odorants) and the control of odorization of natural gas and other

methane rich gases.

NOTE The general requirements for odorants, and the physical and chemical properties of commonly used

odorants are specified in ISO 13734.
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2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute

provisions of this Technical Specification. For dated references, subsequent amendments to, or revisions

of, any of these publications do not apply. However, parties to agreements based on this Technical Report

are encouraged to investigate the possibility of applying the most recent editions of the normative

documents indicated below. For undated references, the latest edition of the normative document

referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.

ISO 5492, Sensory analysis — Vocabulary
ISO 14532, Natural gas — Vocabulary
ISO 5492, Sensory analysis — Vocabulary
ISO 14532, Natural gas — Vocabulary
3 Terms and definitions

For the purposes of this Technical Specification, the terms and definitions given in ISO 5492 and

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ISO 14532 and the following apply:
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3.1.1
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odorant content
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content of the odorant either in the gas or in air expressed as its mass concentration, volume fraction or

mole fraction
3.1.2
odorodour perception
awareness of the effect of volatile substances by the olfactory organ
3.1.3
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ISO/DTSPRF TS 16922:2022(E)
odorodour character
distinctive and identifiable feature of an odorodour or flavour
3.1.4
odorodour intensity
magnitude of the perceived odor
3.1.5
masking

phenomenon by which one or more constituents in the gas stream can change or reduce the odorodour

intensity and/or the odorodour character of the odorized gas
3.1.6
fading of odorant

phenomenon where adsorption, absorption or chemical reactivity of the odorant result in loss of odorant

across the network
4 General requirements
4.1 Necessary odorant addition

Because safety is paramount in the gas industry, it could be assumed that the stronger the odorodour of

gas, the better. However, an upper limit is usually set to avoid unjustified leakage complaints already

caused by the small volume of unburnt gas escaping during ignition of the burner. An excessive

odorization level can also lead to a slight and permanent gas smell related to micro leaks that cannot be

localized and sealed. This could lead to habituation of the customer with the eventuality of a late reaction

when actual leaks occur. Gas odorization is in most countries a legal or regulation requirement that

specifies that natural gas in air be readily detectable by odorodour at a concentration of 20 % (safety

factor of 5) of the lower flammability limit (LFL). The LFL of natural gas is normally taken as a volume

fraction of natural gas in air of 4 % to 5 %. However, local regulations may specify other odorization rules.

NOTE Consider potential masking issues when blending natural gas with other gases (e. g. biomethane, LPG), the

odorodour being either naturally present or artificially added.
4.2 Requirements and parameters for consideration when selecting an odorant
[1]
Information about different odorants is given in informative annex A of .
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Various parameters are considered when selecting an odorant:

— Typical odorodour character that is intense, unpleasant and universally associated with gas

— Physical properties: Freezing point, boiling point, vapour pressure
— Stability:
— Stability with respect to oxidation in network:

Mercaptans being more reactive than sulfides, they tend to form less odorous disulfides in presence

of rust, thus lowering odorization efficiency.
— Stability in storage:
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ISO/DTS PRF TS 16922:2022(E)

Some chemicals developed for odorization displaying reactive function can undergo hazardous

polymerization reaction if not stabilized adequately. Such reaction could occur in storage

tank or within injection system.
— Toxicity
— Environmental issues

— Gas quality: wet gas, presence of other sulphur compounds or network displaying condensates will

generate odorant scrubbing or cross contamination that may affect odorant efficiency

— Odorization practice in the region:
— Centralized / decentralized

— Odorization technique: (some odorants may not be compatible with Bypass odorizers, etc.)

— Network material (Carbon steel, plastics)

The level of the odorant added, that determines the odorodour intensity, is based on different factors

whereof not all are based on measurement, as e.g. local experience. The typical objective is that the

population with a functional sense of smell will be able to smell odorized gas before its concentration

reaches the specified limit (typically 20 % LFL) and thus takes the appropriate measures to protect itself.

Different approaches are applied to define and estimate the concentration of odorant required to achieve

this effect.

The odorodour intensity of an odorant for natural gas or a gas is best determined by the human olfactory

organ.
4.3 Public awareness

In some countries, local regulations require the operators to follow a public awareness program, which

may include specific information about the risk of gas and guidance for leak recognition. The use of

scratch-and-sniff cards containing the encapsulated odorant or other carriers is also frequently used in a

number of countries, but other kind of smell samples are also encountered.

In the case of changing the odour character of the gas odorant, the need to provide adequate information

to the members of the public and gas users should be considered.
5 General remarks on odorant behaviour
5.1 Masking and fading of odorants

Temporary fading in a new gas distribution system or after changing the odorant requires specific

monitoring and can need temporary supplemental odorization or other measures ( e. g. preconditioning).

Some components, e. g. present in some natural gases or biogases may react on or with the odorant

applied, resulting in a major loss of smell of the odorant either by masking effects or by chemical reaction.

5.2 Seals and membranes

Liquid odorants may cause severe swelling or even dissolution of organic materials such as plastics,

elastomeric seals and lubricants. Therefore, in odorization equipment and for joints close to the points

where the liquid odorant is injected into the line, only sealing materials should be used which are

© ISO 2022 – All rights reserved 3
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ISO/DTSPRF TS 16922:2022(E)

compatible with liquid odorants. This information is normally supplied by the manufacturer of the

odorant (see [1]).
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5.3 Pipelines

The low odorant concentrations used for odorization of natural gas do not compromise the integrity of

plastic pipes, seals or diaphragms in gas transportation, distribution and utilization.

When starting gas distribution through new gas lines or when changing the odorant it may take some

time to reach the required odorant concentration at the end of the line. This may result from the odorant

being sorbed on the pipe wall, by pipe dust, rust and incrustations or by gas condensates (odorodour

fading). The degree of sorption depends on several factors, for example the condition of the pipe grid, the

pressure, the temperature, the flow velocity and the physico-chemical properties of odorants.

5.4 Buried pipeline

Odorized gases leaking from gas lines in the ground may lose odorants by sorption in the soil. Sorption

and oxidation of odorants may vary with moisture content and the type of soil. Degradation of odorants

by microorganisms may also occur.
6 Safety precautions
6.1 Handling of odorants

WARNING — Odorants should be handled according to their actual characteristics and prevailing

regulations.

IMPORTANT - — All relevant safety precautions being observed when handling odorants, employees

should be instructed periodically. Odorants are irritating, harmful and flammable. Therefore, the specific

material safety data sheet should be read prior to handling liquid odorants. All safety precautions should

be strictly observed and followed.
A minimum level of safety may be achieved by the following recommendations:

— Concentrated vapours of odorants may cause short-term acute health problems, such as dizziness,

headache, nausea and irritation of throat, nose and eyes. Therefore protection, for example with a

filter containing activated charcoal or a respirator, is common use. Any extended exposure without

respiration protection need to be avoided.

— When handling odorants, suitable personal protective equipment (eye-, face-, body-protection,

gloves) and safe-handling procedures of the odorant are recommended. If, in spite of the use of

personal protection equipment, liquid odorant contacts the skin or the eyes, wash the affected spot

as first aid, immediately with plenty of water. If an eye comes in contact with liquid odorant, consult

a physician immediately.
6.2 Spill management and remediation

WARNING — Undiluted oxidants should never be brought into contact with odorants: RISK OF

EXPLOSION!

There are several possibilities to eliminate the nuisance caused by the strong odorodour of spilled

odorants.
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ISO/DTS PRF TS 16922:2022(E)
— For odorodour
...

TECHNICAL ISO/TS
SPECIFICATION 16922
First edition
Natural gas — Odorization
Gaz naturel — Odorisation
PROOF/ÉPREUVE
Reference number
ISO/TS 16922:2022(E)
© ISO/TS 2022
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ISO/TS 16922:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE © ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 16922:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 General requirements .................................................................................................................................................................................... 2

4.1 Necessary odorant addition ........................................................................................................................................... ............. 2

4.2 Requirements and parameters for consideration when selecting an odorant .............................. 2

4.3 Public awareness .................................................................................................................................................................................. 3

5 General remarks on odorant behaviour ..................................................................................................................................... 3

5.1 Masking and fading of odorants .............................................................................................................................................. 3

5.2 Seals and membranes ....................................................................................................................................................................... 3

5.3 Pipelines ....................................................................................................................................................................................................... 3

5.4 Buried pipeline ....................................................................................................................................................................................... 3

6 Safety precautions.............................................................................................................................................................................................. 4

6.1 Handling of odorants ........................................................................................................................................................................ 4

6.2 Spill management and remediation ..................................................................................................................................... 4

6.3 Transportation and storage ........................................................................................................................................................ 5

7 Odorization technique ...................................................................................................................................................................................5

7.1 Odorization of pipeline networks .......................................................................................................................................... 5

7.1.1 Odorization of transmission pipelines ............................................................................................................ 5

7.1.2 Odorization of distribution pipelines .............................................................................................................. 5

7.1.3 Combined odorization of transmission and distribution pipelines ...................................... 6

7.2 Odorizer ........................................................................................................................................................................................................ 6

7.2.1 General ........................................................................................................................................................................................ 6

7.2.2 Liquid injection odorizers .......................................................................................................................................... 6

7.2.3 Positioning of odorant injectors ........................................................................................................................... 7

7.2.4 Evaporation odorizers ................................................................................................................................................... 7

7.3 Design of installation ........................................................................................................................................................................ 8

7.3.1 Odorization rooms ............................................................................................................................................................ 8

7.3.2 Ventilation ................................................................................................................................................................................ 8

7.3.3 Installation of injection point and injection pipe .................................................................................. 8

7.3.4 Tank design and operations ..................................................................................................................................... 8

7.3.5 Spill kit ......................................................................................................................................................................................... 9

7.4 Pressure resistance ............................................................................................................................................................................ 9

7.5 Addition of odorant ............................................................................................................................................................................ 9

7.5.1 Control of the addition .................................................................................................................................................. 9

7.5.2 Monitoring and control devices ............................................................................................................................ 9

7.5.3 Testing and commissioning ...................................................................................................................................... 9

8 Control of odorization ....................................................................................................................................................................................9

8.1 General ........................................................................................................................................................................................................... 9

8.2 Check of odorization equipment and systems ......................................................................................................... 10

8.3 Control of odorization of the gas ......................................................................................................................................... 10

8.4 Odour complaints .............................................................................................................................................................................. 10

Bibliography .............................................................................................................................................................................................................................11

iii
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ISO/TS 16922:2022(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.

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 documents 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).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

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 193, Natural gas.

This first edition ISO/TS 16922 cancels and replaces the first edition (ISO/TR 16922:2013), which has

been technically revised.
The main changes are as follows:

— modification of the structure of the Technical Report, new clauses: 4.1, 4.2, 4.3, 5.1, Clause 7, 7.1,

7.1.1, 7.1.2, 7.1.3, 7.3, 7.3.1, 7.3.2, 7.3.3, 7.3.4, 7.3.5;
— modification of 7.2.

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.
PROOF/ÉPREUVE © ISO 2022 – All rights reserved
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ISO/TS 16922:2022(E)
Introduction

Processed natural gas normally has little or no odour. For safety reasons distributed natural gas is

therefore be odorized, to permit the detection of the gas by smell.

The odorization is predominantly a safety measure for the user of natural gas. Odorized natural gas

needs to be recognized by the characteristic smell.

This document may also be applied to other gases used in gas supply as e.g. biomethane, blends

containing hydrogen, regasified LNG or LBG, LPG for conditioning in gas supply, etc.

© ISO 2022 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 5 ----------------------
TECHNICAL SPECIFICATION ISO/TS 16922:2022(E)
Natural gas — Odorization
1 Scope

This document gives the specifications and guidelines for the methods to be used in the odorization of

natural gas and other methane rich gases delivered through natural gas networks to gas applications

under a safety point of view.

This document also specifies the principles for the odorization technique (including handling and

storage of odorants) and the control of odorization of natural gas and other methane rich gases.

NOTE The general requirements for odorants, and the physical and chemical properties of commonly used

odorants are specified in ISO 13734.
2 Normative references

The following normative documents contain provisions which, through reference in this text,

constitute provisions of this Technical Specification. For dated references, subsequent amendments

to, or revisions of, any of these publications do not apply. However, parties to agreements based on

this Technical Report are encouraged to investigate the possibility of applying the most recent

editions of the normative documents indicated below. For undated references, the latest edition of the

normative document referred to applies. Members of ISO and IEC maintain registers of currently valid

International Standards.
ISO 5492, Sensory analysis — Vocabulary
ISO 14532, Natural gas — Vocabulary
3 Terms and definitions

For the purposes of this Technical Specification, the terms and definitions given in ISO 5492 and

ISO 14532 and the following apply:
3.1.1
odorant content

content of the odorant either in the gas or in air expressed as its mass concentration, volume fraction or

mole fraction
3.1.2
odour perception
awareness of the effect of volatile substances by the olfactory organ
3.1.3
odour character
distinctive and identifiable feature of an odour or flavour
3.1.4
odour intensity
magnitude of the perceived odour
3.1.5
masking

phenomenon by which one or more constituents in the gas stream can change or reduce the odour

intensity (3.1.4) and/or the odour character (3.1.3) of the odorized gas
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3.1.6
fading of odorant

phenomenon where adsorption, absorption or chemical reactivity of the odorant result in loss of

odorant across the network
4 General requirements
4.1 Necessary odorant addition

Because safety is paramount in the gas industry, it could be assumed that the stronger the odour of gas,

the better. However, an upper limit is usually set to avoid unjustified leakage complaints already caused

by the small volume of unburnt gas escaping during ignition of the burner. An excessive odorization

level can also lead to a slight and permanent gas smell related to micro leaks that cannot be localized

and sealed. This could lead to habituation of the customer with the eventuality of a late reaction when

actual leaks occur. Gas odorization is in most countries a legal or regulation requirement that specifies

that natural gas in air be readily detectable by odour at a concentration of 20 % (safety factor of 5) of

the lower flammability limit (LFL). The LFL of natural gas is normally taken as a volume fraction of

natural gas in air of 4 % to 5 %. However, local regulations may specify other odorization rules.

NOTE Consider potential masking issues when blending natural gas with other gases (e.g. biomethane, LPG),

the odour being either naturally present or artificially added.
4.2 Requirements and parameters for consideration when selecting an odorant
Information about different odorants is given in ISO 13734:2013, Annex A.
Various parameters are considered when selecting an odorant:

— Typical odour character that is intense, unpleasant and universally associated with gas

— Physical properties: Freezing point, boiling point, vapour pressure
— Stability:
— Stability with respect to oxidation in network:

Mercaptans being more reactive than sulfides, they tend to form less odorous disulfides in presence

of rust, thus lowering odorization efficiency.
— Stability in storage:

Some chemicals developed for odorization displaying reactive function can undergo hazardous

polymerization reaction if not stabilized adequately. Such reaction could occur in storage tank

or within injection system.
— Toxicity
— Environmental issues

— Gas quality: wet gas, presence of other sulphur compounds or network displaying condensates will

generate odorant scrubbing or cross contamination that may affect odorant efficiency

— Odorization practice in the region:
— Centralized / decentralized

— Odorization technique: (some odorants may not be compatible with Bypass odorizers, etc.)

— Network material (Carbon steel, plastics)
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The level of the odorant added, that determines the odour intensity, is based on different factors

whereof not all are based on measurement, as e.g. local experience. The typical objective is that the

population with a functional sense of smell will be able to smell odorized gas before its concentration

reaches the specified limit (typically 20 % LFL) and thus takes the appropriate measures to protect

itself. Different approaches are applied to define and estimate the concentration of odorant required to

achieve this effect.

The odour intensity of an odorant for natural gas or a gas is best determined by the human olfactory

organ.
4.3 Public awareness

In some countries, local regulations require the operators to follow a public awareness program, which

may include specific information about the risk of gas and guidance for leak recognition. The use of

scratch-and-sniff cards containing the encapsulated odorant or other carriers is also frequently used in

a number of countries, but other kind of smell samples are also encountered.

In the case of changing the odour character of the gas odorant, the need to provide adequate information

to the members of the public and gas users should be considered.
5 General remarks on odorant behaviour
5.1 Masking and fading of odorants

Temporary fading in a new gas distribution system or after changing the odorant requires specific

monitoring and can need temporary supplemental odorization or other measures ( e.g. preconditioning).

Some components, e.g. present in some natural gases or biogases may react on or with the odorant

applied, resulting in a major loss of smell of the odorant either by masking effects or by chemical

reaction.
5.2 Seals and membranes

Liquid odorants may cause severe swelling or even dissolution of organic materials such as plastics,

elastomeric seals and lubricants. Therefore, in odorization equipment and for joints close to the points

where the liquid odorant is injected into the line, only sealing materials should be used which are

compatible with liquid odorants. This information is normally supplied by the manufacturer of the

odorant (see ISO 13734).
5.3 Pipelines

The low odorant concentrations used for odorization of natural gas do not compromise the integrity of

plastic pipes, seals or diaphragms in gas transportation, distribution and utilization.

When starting gas distribution through new gas lines or when changing the odorant it may take

some time to reach the required odorant concentration at the end of the line. This may result from

the odorant being sorbed on the pipe wall, by pipe dust, rust and incrustations or by gas condensates

(odour fading). The degree of sorption depends on several factors, for example the condition of the pipe

grid, the pressure, the temperature, the flow velocity and the physico-chemical properties of odorants.

5.4 Buried pipeline

Odorized gases leaking from gas lines in the ground may lose odorants by sorption in the soil. Sorption

and oxidation of odorants may vary with moisture content and the type of soil. Degradation of odorants

by microorganisms may also occur.
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6 Safety precautions
6.1 Handling of odorants

WARNING — Odorants should be handled according to their actual characteristics and prevailing

regulations.

IMPORTANT — All relevant safety precautions being observed when handling odorants,

employees should be instructed periodically. Odorants are irritating, harmful and flammable.

Therefore, the specific material safety data sheet should be read prior to handling liquid

odorants. All safety precautions should be strictly observed and followed.
A minimum level of safety may be achieved by the following recommendations:

— Concentrated vapours of odorants may cause short-term acute health problems, such as dizziness,

headache, nausea and irritation of throat, nose and eyes. Therefore protection, for example with a

filter containing activated charcoal or a respirator, is common use. Any extended exposure without

respiration protection need to be avoided.

— When handling odorants, suitable personal protective equipment (eye-, face-, body-protection,

gloves) and safe-handling procedures of the odorant are recommended. If, in spite of the use of

personal protection equipment, liquid odorant contacts the skin or the eyes, wash the affected spot

as first aid, immediately with plenty of water. If an eye comes in contact with liquid odorant, consult

a physician immediately.
6.2 Spill management and remediation

WARNING — Undiluted oxidants should never be brought into contact with odorants: RISK OF

EXPLOSION!

There are several possibilities to eliminate the nuisance caused by the strong odour of spilled odorants.

— For odour mitigation, deodorants may be used, which normally do not change the chemical properties

of the odorant. Therefore, health risks will not be eliminated. For larger amounts of spilled odorants

these masking compounds are not suitable.

— Minor quantities of spilled odorants (surface cleaning) can be treated with different options:

— oxidized to less smelling compounds utilizing a procedure incorporating the spraying of diluted

solutions of an oxidant such as 5 % by mass of sodium hypochlorite or 5 % by mass of hydrogen

peroxide, preferably under the addition of detergents. This procedure should account for the

corrosive and reactive nature of these oxidants.

— neutralized with enzymatic solutions, only effective for some odorants (e.g. mercaptans)

— Larger quantities of spilled or leaked odorants should be sorbed by sorbents (activated charcoal)

and disposed of in tightly shut containers. Small remainders should be treated as minor quantities.

These sorbents or soil contaminated by odorants should be treated according to prevailing regulations.

Commercial products are also available to mask and/or mitigate odorant spillage. These products are

generally available through the odorant manufacturer.

For the cleaning of pipework, containers and parts of the odorizing equipment the use of alcohols

(isopropanol, technical ethanol) is an option. The used cleaning solution are to be disposed according to

prevailing regulations.
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6.3 Transportation and storage

Odorants are delivered in corrosion-resistant containers suitable for transport and/or storage

according to prevailing regulations. Odorant containers need to be accompanied by a safety data sheet

conforming to the requirements of all prevailing regulations.

The use of the proper sealing materials is according to the type of odorant, sulfurous or acrylic.

To avoid nuisance when stationary odorant tanks are refilled, vapour equalization lines for gas phase

transfer between storage and transportation tanks are recommended. Lines for transfer equipped with

automatic shutoff valves are recommended, where possible. Connections and valves preferably have

minimum dead volume.

Storage rooms for odorant containers are best cool, dry and well ventilated. Extended impact of the sun

increase of the internal pressure of odorant containers during transport and/or storage.

Storage containers and the odorizing plant may be in the same room. Odorants jointly with any easily

inflammable substance is best to be avoided.
7 Odorization technique
7.1 Odorization of pipeline networks
7.1.1 Odorization of transmission pipelines

Centralized odorization is performed at the entry point of gas into the transmission network (i.e. LNG

terminal, interconnection points, etc.). Its advantages are:

— the installation, operation and maintenance of sophisticated equipment to automate and monitor

each odorizer is simpler and results in better uniformity of the odorant concentration in the gases;

— it allows a uniform gas odour throughout a region.
Its disadvantages are

— the odorants may have to be removed from the gas supplied to some industrial consumers, and

— odorized gas is delivered to industrial consumers that may not need it because other safety measures

may be provided to recognize gas leaks (e.g. gas sensors for these industrial processes).

7.1.2 Odorization of distribution pipelines

Decentralised odorization is performed typically at the entry points of the distribution networks,

including biomethane injection points. Advantages for decentralized odorization are:

— odorant concentrations can be adjusted to the specific conditions of the local distribution grid (new

pipes or old pipes with deposits),

— the sulfur content of gas for industrial use or the environmental effects of odorants on some types

of underground storage are not increased by odorization by avoiding unnecessary odorization.

Disadvantages of decentralized odorization are
— the multiplicity of odorization stations, generally close to populated areas,
— generation of transportation of odorant on road or rail, and
— handling of odorant by a multitude of personnel,
— low gas flow is more difficult to follow up in odorant dosage.
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7.1.3 Combined odorization of transmission and distribution pipelines

In some countries, classification of transmission pipelines is enforced according to the human

occupancy on either side of the pipelines, defining which pipelines have to be odorized. In a number of

countries, odorization is mandatory when the human occupancy is high.

In some cases, minimum odorization levels in transmission and distribution are different. In other cases,

where different odorants are in use and the possibility exists to transfer odorized gas from distribution

to transmission grids (in case of biomethane overproduction) it may be required to deodorize the gas.

7.2 Odorizer
7.2.1 General
Odorization is usually performed using one of the following techniques:
— liquid odorant injection;
— evaporation odorizer.
7.2.2 Liquid injection odorizers

To allow for a constant odorization, the necessary amount of odorant is added to the gas stream

continuously or quasi continuously. This is best accomplished by flow proportional odorization by

injection odorizers. Flow proportioning refers to adjusting the odorant injection rate to the flowrate of

the gas flowing in the pipeline. These odorizers are typically the most commonly used nowadays, and

can be sized to fit most flowrates.

Odorant is injected from a storage tank, generally maintained at low pressure, directly into the flowing

gas. In principle, two systems are commonly in use:

a) Systems with injection pumps: the injection rate is related to the volumetric pump displacement

and the stroke frequency. This frequency is adjusted by accounting for the gas flow as measured by

a measurement device. The pump protected by an upstream filter against clogging.

b) Valve-controlled systems: Gas-flow proportional injection from a pressurized storage tank may be

achieved by means of mass-flow or volume-flow controllers.

The injection of odorant may also be regulated by taking into account the actual odorant concentration

present in the gas. The injection system also can produce information regarding the total odorant

injected, injection rate, and alarms regarding the performance of the system.

The liquid odorant can be injected into an injection probe. Designs of these probes vary but are intended

to maximize vaporization of the odorant into the natural gas. Filters are normally installed upstream

to the injection system in order to decrease the required maintenance of the system. A check valve and

isolation valve should be installed in the connection line between the injection system and the injection

point.

All material in contact with liquid odorants should be assessed for compatibility with the specific

odorant in accordance with the odorant manufacturer’s information. Such assessment is therefore also

performed when the type of odorant is changed.
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