IGEM/UP/1B Edition 4

Quick reference: IGEM/UP/1B Edition 4 at a glance

 

What is IGEM/UP/1B Edition 4

IGEM/UP/1B is an IGEM utilisation standard covering tightness testing and direct purging of small LPG/Air, natural gas (NG) and LPG installations. Edition 4 was published in March 2026 and supersedes IGEM/UP/1B Edition 3 (Communication 1759).

The standard applies to sections of installation pipework, including meters, where all of the following apply:

• Maximum operating pressure (MOP) at the outlet of the emergency control valve (ECV) not exceeding 2 bar for NG and LPG/Air.
• Nominal bore not greater than 35 mm (DN32, R1¼).
• Meter badged capacity not exceeding 16 m³/h.
• Installation volume (IV) supplying an individual dwelling or non‑domestic premises not exceeding 0.035 m³.
• For NG and LPG/Air: nominal operating pressure at the outlet of the primary meter not exceeding 21 mbar.
• For LPG: nominal operating pressure at the outlet of the final stage regulator not exceeding 37 mbar.

It covers installations supplied with LPG/Air, NG or LPG, including those without a meter, within these size and pressure limits.

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Who and what does IGEM/UP/1B Edition 4 apply to?

Edition 4 applies to installation pipework containing:

• LPG/Air.
• Natural gas, including blends with up to 20% hydrogen.
• LPG.

It includes installation pipework and meters meeting the MOP, bore, meter capacity and volume limits set out in the scope.

The standard specifically covers installations in:

• Individual dwellings.
• Non‑domestic premises, provided the IV is ≤ 0.035 m³.
• Caravans and Leisure Accommodation Vehicles (LAVs).

For small LPG installations on boats, yachts and similar craft, PD 54823 or BS EN ISO 10239 apply instead.

Where the installation volume exceeds 0.035 m³, the work falls under IGE/UP/1 rather than IGEM/UP/1B Edition 4. For certain meter installations up to 1 m³ and 7 bar, IGEM/UP/1C may be the more appropriate standard.

When do you use IGEM/UP/1B Edition 4?

The standard applies to tightness testing in the following situations:

• New installations.
• Alteration, replacement, re‑use or upgrading of existing installations.
• New extensions to existing pipework.
• Before and after any work that may affect gas tightness.
• Where there is a known or suspected gas escape.
• Following complete loss of supply pressure (upstream of the ECV) or loss of installation pressure.
• Routine testing of existing installations.
• Immediately before purging installations, except when taking components permanently out of service.

The same standard applies to direct purging where there is a risk of air (or other gases) being present in the installation, including new work, modifications and cases of complete loss of installation pressure.

Routine servicing alone may not always require application of the full standard, but engineers must use competent judgement to decide whether tightness testing and/or purging is necessary.

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Key changes in IGEM/UP/1B Edition 4

Edition 4 brings some significant technical and practical changes compared with Edition 3. These changes affect how engineers assess tightness, select permissible pressure drops and decide which standard to apply.

1. Installation volume now drives tightness testing limits

One of the most important changes is how permissible pressure drops are determined. Under Edition 3, engineers often worked from meter‑based tables (for example, U6 or U16) to decide whether a pressure drop was acceptable.

Edition 4 shifts this towards installation volume:

• Permissible pressure drops on a tightness test are now dictated by the Installation Volume (IV), not just the meter size.
• Any perceptible movement on the gauge must be treated carefully and cannot simply be written off using meter‑size-based allowances.
• Engineers may need to calculate the IV of all or part of the installation to confirm whether a pressure change is within acceptable limits.

This brings NG testing into line with the more rigorous volume‑based approach already familiar to many engineers working with LPG.

For many domestic properties, the whole installation will still fall below 0.035 m³, but engineers must confirm this rather than assume. The standard gives example pipework runs that fall within 0.035 m³, such as 25 m of 35 mm copper pipework with a U6 meter, to help with initial judgment.

2. Confirmed scope and limits

Edition 4 is clearer and more prescriptive about where IGEM/UP/1B applies and where other standards must be used. Key points include:

• Tightness testing and direct purging of LPG/Air, NG and LPG installations with MOP at the ECV ≤ 2 bar for NG and LPG/Air.
• Nominal bore ≤ 35 mm and IV ≤ 0.035 m³ for installations within scope.
• Specific operating pressure limits for NG, LPG/Air and LPG at the outlet of the meter or regulator, as noted above.
• Explicit cross‑references to IGE/UP/1, IGEM/UP/1C, PD 54823 and BS EN ISO 10239 for installations that fall outside these limits or in particular locations.

The standard also emphasises that LPG service pipework is outside its scope and is covered by Liquid Gas UK Code of Practice 22.

3. Caravans and Leisure Accommodation Vehicles (LAVs) formally included

While earlier editions were focused on domestic and small commercial premises, Edition 4 explicitly includes installations on Caravans and Leisure Accommodation Vehicles. This means:

• Engineers working on gas supplies to touring caravans, static vans and similar leisure units must now align with IGEM/UP/1B Edition 4 where the scope conditions are met.
• The same tightness testing and direct purging principles apply, with appropriate consideration of the installation volume and operating pressures.

For boats and certain other leisure craft, PD 54823 or BS EN ISO 10239 still apply, not IGEM/UP/1B.

4. Hydrogen‑ready scope

Edition 4 recognises that NG may contain up to 20% hydrogen by blend. The standard confirms that, for the purposes of IGEM/UP/1B, NG includes blends up to this level, so the testing and purging principles apply to hydrogen‑enriched networks that fall within the pressure, volume and bore limits.

This is an important detail for engineers operating in hydrogen‑trial areas or where future conversion to blended supplies is planned.

5. Human factors, competence and terminology

The introduction to IGEM/UP/1B Edition 4 puts renewed emphasis on:

• The legal responsibilities of employers to ensure that “responsible engineers” are competent and properly supported.
• The need for systems and procedures that monitor and review professional judgement.
• Human factors as a contributor to incidents, referencing HSE guidance such as HSG48 and HSG65.

The standard uses “must”, “shall” and “should” in a defined way, and stresses that new and better techniques should be adopted without waiting for formal amendments where they are proven and within the responsible engineer’s competence.

Transition dates: When does IGEM/UP/1B Edition 4 become mandatory?

IGEM/UP/1B Edition 4 is published with a built‑in transition period to allow the industry to adapt.

• Publication date: March 2026.
• Edition 3 withdrawal date: 30 September 2026.
• Edition 4 effective date: 1 October 2026.

During the transition window from publication to 30 September 2026, both Edition 3 and Edition 4 are technically available. However, IGEM expects gas operatives to adopt the Edition 4 procedures as soon as reasonably practicable, and Edition 4 becomes the required standard from 1 October 2026.

Gas Safe has indicated via industry updates that inspections during the transition will recognise either standard, but that from 1 October 2026 engineers will be expected to follow IGEM/UP/1B Edition 4.

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Practical implications for gas engineers

For practising engineers, the real question is how IGEM/UP/1B Edition 4 will change day‑to‑day work. The main practical impacts are around test planning, calculation and record‑keeping.

Before you start work

The standard reinforces the importance of preparation and risk management:

• Risk assessment and method statement: carry out and document a proportionate risk assessment for the work, including purging operations and any potential sources of ignition.
• Site survey: complete a survey of the installation and surrounding area to identify hazards, access issues and any factors that could influence testing or purging.
• Communication with occupier: inform the occupier or responsible person about the work, any defects identified and safety precautions.
• Equipment check: confirm that tools, materials and test equipment are suitable, calibrated where required and in good condition.

These preparatory steps are not new concepts, but Edition 4 places more emphasis on them as integral parts of safe testing and purging.

Tightness testing under Edition 4

While the detailed procedures remain within the paid standard, the key messages are:

• You must ensure the installation, or the section under test, fits within the IGEM/UP/1B scope (pressure, bore, meter capacity and IV limits) before using the Edition 4 procedures.
• Permissible pressure drops are now based on the installation volume rather than meter size alone, particularly for NG installations.
• Any perceptible movement on a pressure gauge requires investigation and must not be automatically attributed to meter tolerances or temperature changes.
• The standard continues the long‑standing approach that strength testing is not required for components operating at ≤ 75 mbar within its scope, provided the materials and construction methods are appropriate.

Engineers will therefore need to be comfortable calculating installation volume (for example, using lengths and diameters of pipework, including flexible corrugated stainless‑steel tube where used) and relating this to the Edition 4 acceptance criteria.

Direct purging

Edition 4 covers direct purging for LPG/Air, NG and LPG installations within its scope in cases such as new installations, modifications, extensions and loss of pressure. It highlights that purging is required where air (or other gases) may be present and that procedures must be adjusted if another gas is being displaced, such as during fuel conversions.

The standard underlines that purging operations must be risk assessed, planned and controlled, with suitable provision for safe discharge and ventilation. Engineers must also consider how hydrogen blends may influence purging behaviour in NG systems, although the core principles remain the same within the defined limits.

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How Logic4training can help

At Logic4training, we will update our gas training to reflect the IGEM/UP/1B Edition 4 later on in the year. Our aim is to help engineers move smoothly from Edition 3 to Edition 4, with a focus on practical skills such as installation volume calculation and applying the correct permissible pressure drops.

If you are working with small NG or LPG installations in domestic, light commercial, caravan or LAV settings, it is sensible to familiarise yourself with IGEM/UP/1B Edition 4 now, ahead of the October 2026 deadline.

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FAQs

When does IGEM/UP/1B Edition 4 come into force?

Edition 4 was published in March 2026 and becomes effective from 1 October 2026. IGEM/UP/1B Edition 3 remains available during the transition period but is withdrawn on 30 September 2026.

Can I still use IGEM/UP/1B Edition 3?

Yes, during the transition window up to 30 September 2026 you can work to either Edition 3 or Edition 4, provided you apply the chosen standard correctly. From 1 October 2026, Edition 4 is the version expected to be used for in‑scope installations.

Which gas installations does IGEM/UP/1B Edition 4 cover?

The standard covers small LPG/Air, NG and LPG installations, with or without a meter, provided they meet all of the following: MOP at the ECV not exceeding 2 bar (NG and LPG/Air), nominal bore ≤ 35 mm, meter badged capacity ≤ 16 m³/h and installation volume ≤ 0.035 m³. It applies to individual dwellings, certain non‑domestic premises, caravans and Leisure Accommodation Vehicles (LAVs) within these limits.

What is the 0.035 m³ installation volume limit?

The 0.035 m³ installation volume (IV) limit defines the upper size of installation that falls within IGEM/UP/1B Edition 4. If the installation volume is above 0.035 m³, the work should be carried out to IGE/UP/1 rather than IGEM/UP/1B.

Why is installation volume so important in Edition 4?

Edition 4 uses installation volume as the key factor in determining permissible pressure drops on tightness tests instead of relying mainly on meter‑based tables. This volume‑based approach helps engineers assess pressure changes more accurately, particularly on NG systems, and mirrors the methods already familiar in LPG work.

Does IGEM/UP/1B Edition 4 cover caravans and LAVs?

Yes, Edition 4 explicitly includes installations on caravans and Leisure Accommodation Vehicles, as long as they meet the pressure, bore, meter capacity and installation volume limits in the scope. For small LPG systems on boats and similar craft, PD 54823 or BS EN ISO 10239 remain the relevant standards instead of IGEM/UP/1B.

How does IGEM/UP/1B Edition 4 deal with hydrogen blends?

For the purposes of IGEM/UP/1B Edition 4, natural gas includes blends containing up to 20% hydrogen. The tightness testing and direct purging principles in the standard therefore apply to hydrogen‑enriched NG networks that still fall within the stated pressure, bore and IV limits.

When should I use IGEM/UP/1B rather than other UP standards?

Use IGEM/UP/1B Edition 4 for tightness testing and direct purging of small LPG/Air, NG and LPG installations that sit within the scope limits for MOP, bore, meter capacity and IV. Where the installation volume is above 0.035 m³, IGE/UP/1 applies, and for certain meter installations up to 1 m³ and 7 bar, IGEM/UP/1C may be more appropriate.

In what situations must I tightness test or purge under Edition 4?

Edition 4 applies to tightness testing and direct purging for new installations, alterations, replacements, re‑use, upgrades, extensions, known or suspected gas escapes, complete loss of supply or installation pressure, routine testing and immediately before purging. Engineers must use competent judgement to decide when servicing work also warrants testing and/or purging.

What are the main practical changes for tightness testing?

Practically, engineers now need to confirm the installation falls within the Edition 4 scope and calculate installation volume where necessary before choosing permissible pressure drops. Any perceptible movement on the gauge must be investigated rather than written off against meter tolerances, and records should clearly show how IV and acceptance criteria were determined.

Does IGEM/UP/1B Edition 4 change purging requirements?

The core principles of direct purging remain, but Edition 4 reinforces the need to purge whenever air or other gases may be present and to adjust procedures if one gas is being displaced by another. It also stresses that purging must be risk assessed, planned and controlled, with safe discharge and ventilation arrangements in place.

How does IGEM/UP/1B Edition 4 address competence and human factors?

Edition 4 strengthens the language around employer responsibilities, stating that responsible engineers must be competent, properly supported and subject to monitoring and review. It also highlights human factors as a key part of incident prevention and references HSE guidance such as HSG48 and HSG65.

How is Logic4training supporting engineers with IGEM/UP/1B Edition 4?

Logic4training is updating its gas training, reassessment and CPD to reflect IGEM/UP/1B Edition 4 so engineers can apply the new requirements confidently on site. Training will focus on installation volume calculation, choosing the correct permissible pressure drops and understanding how IGEM/UP/1B interacts with related standards such as IGE/UP/1 and IGEM/UP/1C.