1.1 This Standard was published in March 2026 and will supersede IGEM/UP/1B Edition 3, Communication 1759.
IGEM/UP/1B Edition 4 is published with the expectation that gas operatives will adopt the procedures as soon as reasonably practicable, but in all circumstances, it will become effective from 1st October 2026. During the period up to 1st October 2026, IGEM/UP/1B Edition 3 will remain available for use but will be withdrawn on 30th September 2026.

1.2 This Standard has been drafted by a Panel appointed by the Institution of Gas Engineers and Managers’ (IGEM’s) Gas Utilisation Committee, subsequently approved by that Committee and published by the authority of the Council of the Institution.

1.3 IGE/UP/1 deals with all aspects of strength and tightness testing and direct purging of selected 1st, 2nd and 3rd family gases within its wide scope and at a maximum operating pressure (MOP) not exceeding 16 bar.
IGE/UP/1A deals with the special case of strength and tightness testing and direct purging of volumes not exceeding 1 m3 and operating pressure (OP) not exceeding 40 mbar and using Natural Gas (NG).
IGEM/UP/1B Edition 4 deals with all aspects of tightness testing and direct purging of small Liquefied Petroleum Gas/Air (LPG/Air), NG and Liquefied Petroleum Gas (LPG) installations with or without a meter of maximum badged capacity not exceeding 16 m3/h and supply MOP (MOPu) not exceeding 2 bar.

Note: In the United Kingdom, LPG/Air is typically 1st family gas, NG is 2nd family gas and LPG is a 3rd family gas. NG is lighter than air and LPG/Air and LPG are both heavier than air.

IGEM/UP/1B Edition 4 also covers installations on Caravan and Leisure Accommodation Vehicles (LAVs). For tightness testing of small LPG installations in boats, yachts, crafts and other vessels, PD 54823 or BS EN ISO 10239 apply, as appropriate. For volumes exceeding 0.035 m3, IGE/UP/1 applies.
IGEM/UP/1C deals with strength testing, tightness testing and direct purging of meter installations (as defined in IGEM/G/1), containing either NG or LPG, of volume not exceeding 1 m3 and MOP not exceeding 7 bar.

Note: IGEM/UP/1C is most useful for those NG or LPG meter installations that have a means of isolation on the outlet, are out of scope of IGEM/UP/1B and where there is no desire to test the installation pipework downstream of the meter installation.
Figure 1 will assist in selecting the appropriate standard.
Note: For a new system of installation pipework, the onus is on the designer to establish both the maximum incidental pressure (MIP) and MOP. For an existing system of installation pipework, the onus is on the designer/owner of the installation to ensure that any increase in pressure within the installation will not result in OP exceeding MOP of the system and on the gas transporter/meter asset manager (GT/MAM) to ensure that any change in their pressure regimes due to fault conditions will not jeopardise the safety of the downstream installation. This involves effective communication between the GTs/MAMs and installation designers/owners.

1.4 This Standard makes use of the terms “must”, “shall” and “should” when prescribing particular requirements. Notwithstanding Sub-Section 1.7:

• the term “must” identifies a requirement by law in Great Britain (GB) at the time of publication
• the term “shall” prescribes a requirement that, it is intended, will be complied with in full and without deviation
• the term “should” prescribes a requirement that, it is intended, will be complied with unless, after prior consideration, deviation is considered to be acceptable.

Such terms may have different meanings when used in Legislation, or Health and Safety Executive (HSE) Approved Codes of Practice (ACoPs) or Guidance, and reference needs to be made to such statutory Legislation or official Guidance for information on legal obligations.

1.5 The primary responsibility for compliance with legal duties rests with the employer. The fact that certain employees, for example “responsible engineers”, are allowed to exercise their professional judgement does not allow employers to abrogate their professional responsibilities. Employers are required to:

• have done everything to ensure, so far as is reasonably practicable, that there are no better protective measures that can be taken other than relying on exercise of professional judgement by “responsible engineers”
• have done everything to ensure, so far as is reasonably practicable, that “responsible engineers” have the skills, training, experience and personal qualities necessary for the proper exercise of professional judgement
• have systems and procedures in place to ensure that the exercise of professional judgement by “responsible engineers” is subject to appropriate monitoring and review
• not require “responsible engineers” to undertake tasks which would necessitate the exercise of professional judgement that is not within their competence. There should be written procedures defining the extent to which “responsible engineers” can exercise their professional judgement. When “responsible engineers” are asked to undertake tasks which deviate from this, they are to refer the matter for higher review.

1.6 It is now widely accepted that the majority of accidents in industry generally are, in some measure, attributable to human as well as technical factors. People who initiated actions that caused or contributed to accidents might have acted in a more appropriate manner to prevent them.

To assist in the control of risk and proper management of these human factors, due regard is to be taken of HSG48 and HSG65.

1.7 Notwithstanding Sub-Section 1.4, this Standard does not attempt to make the use of any method or specification obligatory against the judgement of the responsible engineer. Where new and better techniques are developed and proved, they should be adopted without waiting for modification to this Standard. Amendments to this Standard will be issued when necessary, and their publication will be announced in the Journal of the Institution and other publications as appropriate.
Licensed for use by SGN only

1.8 Requests for interpretation of this Standard in relation to matters within its scope, but not precisely covered by the current text, are to be either be;

• addressed in writing to Technical Services, IGEM, IGEM House, 26 & 28 High Street, Kegworth, Derbyshire, DE74 2DA; or
• emailed to.

These will be submitted to the relevant Committee for consideration and advice, but in the context that the final responsibility is that of the engineer concerned. If any advice is given by or on behalf of IGEM, this does not imply acceptance of liability for the consequences and does not relieve the responsible engineer of any of his or her obligations.

1.9 This Standard was published in March 2026.

This Standard applies to LPG/Air, NG, and LPG installations as illustrated in Figure 3.
Note: For the purpose of this Standard, NG includes a blend of NG with up to 20% Hydrogen.

2.2 This Standard applies to any section of installation pipework, including meters, having the following:

• MOP at the outlet of the emergency control valve (ECV) not exceeding 2 bar for NG and LPG/Air, and
• a nominal bore not exceeding 35 mm (DN32, R1¼), and
• a meter with a badged capacity not exceeding 16 m3/h, and
• an installation volume (IV) supplying an individual dwelling or non-domestic premises not exceeding 0.035 m3, and
• LPG/Air Installations - nominal OP at the outlet of the primary meter and any point in the section to be tested not exceeding 21 mbar, or
• NG Installations - nominal OP at the outlet of the primary meter and any point in the section to be tested not exceeding 21 mbar, or
• LPG Installations - nominal OP at the outlet of the final stage regulator and any point in the section to be tested not exceeding 37 mbar.

Note 1: The principles may be used for similar installations with a meter inlet valve (MIV) having a MOPu ≤ 7 bar but suitable adjustments to stated parameters and steps in this Standard will need to be considered by a competent person.
Note 2: There are some existing NG installations, where MOPu exceeds 75 mbar, that have been installed without the facility of a MIV. These installations are not within the scope of IGEM/UP/1B but advice on testing and purging is given in Appendix 4.
Note 3: Installations of volumes greater than 0.035 m3 are rare in domestic premises. However, if there is any doubt, it is advisable to calculate IV in accordance with Appendix 7 before using this Standard.
Note 4: LPG service pipework is not within scope of this Standard and is covered by Liquid Gas UK Code of Practice 22.
Note 5: Propane and Butane installations typically operate at 37 mbar and 28 mbar.
Note 6: The scope of this Standard limits the IV to 0.035 m3. For example, the following installations have a volume less than 0.035 m3:

•  25 m of 35 mm copper pipework (assuming U6 fitted)
•  10 m of 35 mm copper pipework (assuming U16 fitted)
•  20 m of 32 mm pliable corrugated (stainless-steel) tube pipework (assuming U6 fitted)
•  8 m of 32 mm pliable corrugated (stainless-steel) tube (assuming U16 fitted).

2.3 This Standard covers tightness testing and direct purging of pipework containing either LPG/Air, NG, or LPG
.
Note 1: There are Standards for other installation locations which are not individual dwellings – PD 54823, or BS EN ISO 10239 or IGEM/UP/1 apply, as appropriate (see Figure 1).

Note 2: Historically, BS 6891 (which preceded IGE/UP/1B Edition 1 for “soundness testing”) and IGEM/UP/1B Edition 1, 2 and 3 have not required strength testing. This philosophy continues for IGEM/UP/1B Edition 4 (for components of MOP ≤ 75 mbar) as there is no significant case evidence for introducing strength testing, the risk associated with failure of integrity is comparatively low (due to low energy contained) and the available materials and methods of construction are such as to give confidence that integrity will be assured. Steps are given in the tightness test section to check that jointing has been correctly carried out.

2.4 This Standard applies to tightness testing in the following circumstances:

•  new installations
•  alteration to, replacement of, or re-use of, existing installations
•  new extensions to existing pipework
•  prior to and after any work on existing installations that may affect the gas tightness
•  where there is a known or suspected gas escape
•  where there has been a complete loss of supply pressure i.e. upstream of the ECV, or of installation pressure
•  routine testing of existing installations
•  immediately before purging of installations (except when taking components permanently out of service).

Note: This Standard may not need to be applied when carrying out routine maintenance, such as servicing.
2.5 This Standard applies to direct purging in the following circumstances:

•  new installations
•  alteration to, replacement of, or re-use of, existing installations
•  new extensions to existing installations
•  where there has been a complete loss of installation pressure
•  where there is the possibility of extraneous air being present in an installation.

Note 1: This Standard may not need to be applied when carrying out routine maintenance, such as servicing.
Note 2: This Standard refers throughout to purging when there is the possibility air may be present in the gas installation. The principles may be used when there could be other gases in the installation other than the gas with which the installation is currently supplied, for example when an installation is converted from one fuel gas to another, but suitable adjustments to stated parameters and procedures will need to be considered by a competent person.

2.6 All pressures quoted are gauge pressures unless otherwise stated.

2.7 Italicised text is informative and does not represent formal requirements.

2.8 Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections via the prescriptive terms “must”, “shall” or “should”.