Gas tightness testing on commercial premises: when and why

Commercial engineers covering Suffolk, Essex and Cambridgeshire

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A gas tightness test is needed on commercial premises whenever gas pipework is new, altered, extended or re-used, before work on existing pipework, when a gas leak is known or suspected, after the supply has lost pressure completely (for example when the emergency control valve has been shut), immediately before pipework is purged, and as routine testing of existing pipework. Those are the circumstances listed in the scope of the IGEM testing procedures IGE/UP/1 and IGE/UP/1A, and the law adds that anyone who works on installation pipework "which might affect the gastightness of any part of it" must have that part "adequately tested to verify that it is gastight" immediately afterwards. On commercial premises the test is carried out by a Gas Safe registered engineer qualified for the work, never by site staff. This guide explains what a tightness test is, when it is needed, which IGEM procedure applies to your installation, and what duty holders and facilities teams should do.

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Commercial heating tips and advice · 26 October 2026 · Fast Commercial Boiler Help, Gas Safe 985448

What a gas tightness test is

A tightness test checks that a section of gas pipework, including any meter and appliance pipework within the test, is not leaking. IGEM explains that "the terms "soundness testing" (as used in IGE/UP/1 Edition 1) and "tightness testing" have an identical meaning", so you may see either phrase on older paperwork and in manufacturers' manuals.

It is different from a strength test. IGEM says strength testing "has been introduced for new pipework and extensions to ensure that pipework can withstand, with respect to integrity, the pressures it could experience under fault conditions", and that as a result "the subsequent tightness test is carried out at operating pressure (OP)". In short, new pipework and extensions are usually strength tested and then tightness tested; existing pipework is normally tightness tested. Purging, which removes air (or gas) from the pipework safely, is a separate step that follows the testing when gas is being supplied.

When is a gas tightness test needed? The circumstances IGEM lists

The scope of IGE/UP/1 Edition 2 (often written IGEM/UP/1) says its procedures apply to strength and tightness testing of pipework "of any diameter in the following circumstances". IGE/UP/1A Edition 2 lists the same circumstances for smaller installations. In plain terms:

New pipework. A new gas supply to a plant room, kitchen or workshop, or new pipework to a replacement boiler.
Alteration, replacement, re-use or uprating of existing pipework. IGEM gives "increasing OP" as an example of uprating, so a change of operating pressure counts.
New extensions to existing pipework. For example adding a new appliance, a new heater line or a new catering appliance.
Before any work on existing pipework. The engineer tests first so they know the starting condition of the installation before they disturb it.
A known or suspected gas leak. For example a smell of gas or a reported escape.
A complete loss of pressure for any reason. IGEM notes that "The closure of a valve, for example the ECV, can result in a complete loss of pressure which necessitates tightness testing and purging before resumption of supply." So if the emergency control valve has been turned off, or the supply has been cut, the gas should not simply be turned back on.
Routine testing of existing pipework. Testing as part of planned maintenance, not only when something has changed.
Immediately before purging pipework (except when pipework is being taken permanently out of service).

Most of these are triggered by work on the gas installation, so they are usually part of a job your engineer is already doing: an installation, an alteration, a repair or a service. The two that facilities teams most often need to act on are a suspected leak and a supply that has been turned off at the emergency control valve.

What the Gas Safety Regulations require

The Gas Safety (Installation and Use) Regulations 1998 put the testing duty on the person doing the work:

Regulation 22(1): where a person carries out work on installation pipework "which might affect the gastightness of any part of it", they must "immediately thereafter" ensure that part "is adequately tested to verify that it is gastight and examined to verify that it has been installed in accordance with these Regulations".
Regulation 22(2): where gas is being supplied, purging must then be carried out "so as to remove safely all air and gas other than the gas to be supplied", any connection loosened for purging must be retested, and "every seal fitted after such purging is tested for gastightness".
Regulation 33(1): a person installing a gas appliance while gas is being supplied must "immediately thereafter test its connection to the installation pipework to verify that it is gastight", and examine the appliance, including that "all gas safety controls are in proper working order".
Regulation 37(4): where an escape of gas has been stopped by shutting off the supply, "no person shall cause or permit the supply to be re-opened (other than in the course of repair) until all necessary steps have been taken to prevent a recurrence of such escape."

Manufacturers say the same thing in their own words. Ideal's Evomax 2 commercial boiler manual says "The complete installation MUST be tested for gas soundness and purged in accordance with the appropriate standards listed on page 8", lists IGEM/UP/1 among those standards, and tells the engineer that after servicing or replacing components they should always "Test for gas soundness."

Which IGEM procedure applies to your installation?

IGEM publishes different testing procedures for different sizes and types of installation, and the engineer has to check which one fits before testing. IGEM says "It is necessary to check the scope of referenced standards before proceeding."

Procedure	What its scope covers (as IGEM describes it)
IGE/UP/1A Edition 2	Strength and tightness testing and direct purging of Natural Gas installations on industrial and commercial premises with a volume not exceeding 1 m³ (including any meter and an allowance for fittings), an MOP not exceeding 40 mbar at the outlet of the primary meter regulator, a supply MOP not exceeding 75 mbar, and a nominal bore not exceeding 150 mm. Measured from the outlet of the emergency control valve.
IGE/UP/1 Edition 2	Strength and tightness testing and direct purging of pipework with a maximum operating pressure (MOP) not exceeding 16 bar, for Natural Gas from the outlet of the emergency control valve, and for LPG from the outlet of the bulk storage vessel or cylinder valve. IGE/UP/1A says that for a volume over 1 m³, an MOP over 40 mbar, a supply MOP over 75 mbar or a nominal bore over 150 mm, "IGE/UP/1 applies".
IGE/UP/1B	Domestic-sized Natural Gas installations. IGEM says IGE/UP/1A "can be used for pipework exceeding 28 mm diameter on domestic premises".
LPGA TM-62	Tightness testing of domestic-sized LPG pipework (volume not exceeding 0.02 m³). IGEM says "For greater volume, IGE/UP/1 Edition 2 applies."

The design and installation of the pipework itself is covered by a separate standard, IGEM/UP/2 Edition 4, which covers the "design, installation, commissioning, operation, maintenance and decommissioning" of installation pipework on industrial and commercial premises with an MOP not exceeding 60 bar. IGEM notes that BS 6891 "may be utilised on smaller commercial premises that are within its scope". Which documents apply is a decision for your engineer, and it should be clear from their test certificate.

Routine tightness testing and records

IGEM lists "routine testing of existing pipework" as one of the circumstances its procedures cover, but the scope pages do not set a fixed interval. IGEM/UP/2 says that for existing industrial and commercial installations, the Dangerous Substances and Explosive Atmosphere Regulations (DSEAR) "require the completion of a risk assessment", and that "it is essential that they are maintained and inspected as determined by the risk assessment." In practice, agree with your engineer how routine testing fits into your commercial gas safety inspection and planned maintenance, and remember that a boiler service normally ends with a gas soundness check of the appliance (see what a commercial boiler service includes).

IGEM sells blank triplicate certificate pads for strength testing, tightness testing and direct purging to the IGE/UP/1 and IGE/UP/1A procedures, so ask for a written record of each test and keep it with your other gas safety paperwork. Our guide to heating maintenance records explains how to file them so insurers, landlords and auditors can find them.

What site staff should do (and not do)

A tightness test means isolating the gas, pressurising pipework and reading test gauges, and it is followed by purging. That is gas work, and it is for a Gas Safe registered engineer qualified for commercial work only. Site and facilities staff have a different, equally important job:

If you smell gas or suspect a leak, follow HSE's advice: "turn off the supply and immediately phone" the National Gas Emergency Service on 0800 111 999 for natural gas, or your LPG supplier for LPG. HSE adds: "If in doubt, evacuate the building and inform the police as well as the National Gas Emergency Service or your gas supplier."
Do not turn the gas back on after it has been shut off for a leak. HSE says "Do not turn a gas supply back on until a leak has been dealt with by a competent person." If the emergency control valve has been closed for any other reason, ask your engineer before reopening it, because the loss of pressure may itself need a tightness test and purge.
Tell the engineer what has changed: any building or kitchen works near gas pipework, any new or removed appliances, a meter exchange, or a supply interruption. That helps them decide which tests are needed.
Do not test, purge, cap or alter gas pipework yourselves, and do not use leak-detection sprays or gauges as a substitute for a proper test.
After the gas is restored, appliances must be relit and checked by the engineer. Catering ventilation interlocks may need resetting in the normal way (see commercial kitchen gas interlocks), and it is worth checking the heating controls are back on their normal schedules (see BMS and heating controls checks).

Who does what

Task	Who
Report a smell of gas, shut off the supply and call the emergency number	Anyone on site, following HSE's advice and your site procedure
Keep the emergency control valve accessible and know where it is; log supply interruptions and works near gas pipework	Trained site or facilities staff
Strength testing, tightness testing and purging to IGE/UP/1 or IGE/UP/1A; testing appliance connections; relighting and checking appliances	Gas Safe registered engineer qualified for commercial work
Design, installation and alteration of gas pipework to IGEM/UP/2 (or BS 6891 where within scope)	Gas Safe registered engineer qualified for commercial work
Make sure gas pipework is maintained in a safe condition, the people doing gas work are competent, and records are kept	The employer or self-employed person in control of the premises (the duty holder)

Duty holder responsibilities

Regulation 35 of the Gas Safety (Installation and Use) Regulations 1998 requires every employer or self-employed person to ensure that "any gas appliance, installation pipework or flue installed at any place of work under his control is maintained in a safe condition so as to prevent risk of injury to any person." Regulation 3(1) says "No person shall carry out any work in relation to a gas fitting or gas storage vessel unless he is competent to do so", and regulation 3(2) extends the duty to every employer and self-employed person who "has required such work to be carried out at any place of work under his control".

HSE says that in workplaces such as "shops, restaurants, schools and hospitals, work on gas fittings must be carried out by a Gas Safe registered engineer who is qualified to do the work", and that "It’s your responsibility to check a person is registered and is qualified." In factories and certain other premises HSE says the work must be done by a competent person. Our guide on how to check a Gas Safe engineer is qualified for commercial work shows how to check the right categories on an engineer's ID card.

Need gas pipework tested?

If you have had work done near your gas pipework, are planning a new appliance or a commercial boiler installation, run on LPG, or the gas has been turned off at the emergency control valve, call us on 0800 0996 007 or WhatsApp 07947 578332. Our Gas Safe registered engineers (Gas Safe 985448) carry out commercial gas safety inspections and gas safety work on commercial premises. If you smell gas now, call the National Gas Emergency Service on 0800 111 999 first.

Safety note

Under the Gas Safety (Installation and Use) Regulations 1998, gas work must be carried out by a Gas Safe registered engineer, and we apply that rule on every site. Don't attempt DIY work on gas appliances, burners, flues or safety devices. On pressure systems, trained site staff should stick to visual and gauge checks, log the readings and report anything abnormal. Never adjust, cap, plug or test-lift a relief valve yourself.

Talk to a Gas Safe commercial engineer

Fast Commercial Boiler Help is a Gas Safe registered (985448) commercial heating business based at 4 Market Hill, Clare, Sudbury, Suffolk CO10 8NN. Our team of over 10 local engineers covers East Anglia and East London, working on commercial boilers, plant rooms, water heaters, and warm air, radiant and unit heaters. We work on commercial premises only.

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Frequently asked questions

When is a gas tightness test needed on commercial premises?

IGEM's testing procedures IGE/UP/1 and IGE/UP/1A list the circumstances: new pipework; alteration, replacement, re-use or uprating of existing pipework; new extensions; before any work on existing pipework; a known or suspected gas leak; a complete loss of pressure for any reason (for example after the emergency control valve has been closed); routine testing of existing pipework; and immediately before purging. The test must be carried out by a Gas Safe registered engineer qualified for commercial work.

Is a gas tightness test a legal requirement?

Regulation 22 of the Gas Safety (Installation and Use) Regulations 1998 says that anyone who works on installation pipework in a way that might affect its gastightness must immediately ensure that part is adequately tested to verify that it is gastight. Regulation 33 requires a new appliance's connection to the pipework to be tested. IGEM's procedures set out how the tests are done. For routine testing, IGEM/UP/2 says existing industrial and commercial installations should be maintained and inspected as determined by the DSEAR risk assessment.

What is the difference between IGEM/UP/1 and IGEM/UP/1A?

IGE/UP/1A covers smaller, low pressure Natural Gas installations on industrial and commercial premises: a volume up to 1 m³, an MOP up to 40 mbar at the outlet of the primary meter regulator, a supply MOP up to 75 mbar and a nominal bore up to 150 mm. Anything larger, higher pressure or on other gases such as LPG falls under IGE/UP/1, which covers pipework with an MOP up to 16 bar. Your engineer decides which applies.

What is the difference between a strength test and a tightness test?

A strength test checks that new pipework and extensions can withstand the pressures they could see under fault conditions. A tightness test checks the pipework is not leaking and, after a strength test, is carried out at operating pressure. New pipework is usually strength tested then tightness tested; existing pipework is normally tightness tested. Both are gas work for a Gas Safe registered engineer.

Can our maintenance staff carry out a gas tightness test?

No. Testing and purging gas pipework is work on gas fittings. HSE says that in workplaces such as shops, restaurants, schools and hospitals it must be carried out by a Gas Safe registered engineer who is qualified to do the work, and in factories and certain other premises by a competent person. Site staff should report smells of gas, follow HSE's leak advice (turn off the supply and call 0800 111 999 for natural gas) and not turn the gas back on until a competent person has dealt with it.

Sources and further reading