Regulation 26 of the Gas Safety (Installation and Use) Regulations 1998 applies in Great Britain and sets safety precautions for installing gas appliances, including a duty on anyone who works on an appliance to examine the flue, the combustion air supply, the operating pressure or heat input and the safe operation straight afterwards, and to notify any defect.

What regulation 26 covers

Regulation 26, headed “Gas appliances—safety precautions”, applies across Great Britain, meaning England, Scotland and Wales, as legislation.gov.uk marks it. It is one of the practical safety rules within the Gas Safety (Installation and Use) Regulations 1998, sitting alongside the rules on who may carry out gas work. Our guide to checking a Gas Safe engineer covers the registration side. Regulation 26 is about what must actually be done, and not done, when an appliance such as a boiler is installed or worked on.

Rules on installing an appliance

Paragraph (1) says that no person shall install a gas appliance unless it can be used without constituting a danger to any person. Paragraph (2) requires that a flued domestic gas appliance, which includes a typical boiler with a flue, must be connected to the gas supply system only by a permanently fixed rigid pipe, so flexible hoses are not an acceptable connection for a boiler. Paragraph (3) says a used appliance must not be installed without verifying that it is in a safe condition for further use, which matters for second-hand or ex-display boilers. Paragraph (4) prohibits installing an appliance that does not comply with any enactment restricting its supply on safety grounds.

Connection, isolation and approval marks

Paragraph (5) says that a person installing an appliance must not leave it connected to the gas supply unless it can be used safely or is sealed off with an appropriate fitting. Paragraph (6) requires means of shutting off the gas at the inlet to an appliance, unless that is not reasonably practicable. Paragraphs (7) and (8) deal with appliances bearing an indication that they conform to a type approved as meeting safety standards: work must not be done in a way that stops the appliance complying with those standards, and the indication must not be removed or defaced. These provisions are why a boiler should be left either working safely or visibly isolated at the end of a visit.

The four checks after any work

Paragraph (9) applies wherever a person performs work on a gas appliance. Immediately afterwards they must examine the effectiveness of any flue, the supply of combustion air, the operating pressure or heat input (or, where necessary, both), and the operation of the appliance so as to ensure its safe functioning. Where it is not reasonably practicable to examine operating pressure or heat input, the paragraph provides that the appliance’s combustion performance must be examined instead. The engineer must then take all reasonably practicable steps to notify any defect to the responsible person and, where different, the owner of the premises. Where neither can reasonably be notified, the notice goes to the gas supplier for an LPG appliance or to the transporter in any other case.

When the checks do not apply

Paragraph (10) excludes two situations from the post-work examination: the direct disconnection of an appliance’s gas supply, and the purging of gas or air from an appliance or its pipework where that does not adversely affect its safety. An engineer who simply isolates a boiler is therefore not required to run the same set of checks as one who repairs or replaces a component, although the appliance must not be left in a dangerous state under paragraph (5).

What this means for a householder

HSE says anyone employed to work on gas appliances in domestic premises must be Gas Safe registered and competent in that area of gas work, and that all appliances, flues and pipework should be regularly maintained and serviced at least annually by a registered engineer. It advises that it is illegal for anyone to use an appliance they suspect is unsafe. Householders can ask what was checked, and our guide to the Benchmark scheme explains the commissioning record that usually documents the work. If an engineer finds something wrong, the outcome may be classified using the procedure in our guide to immediately dangerous or at risk appliances.

FAQs

Does regulation 26 apply in Scotland and Wales?

Yes. legislation.gov.uk marks regulation 26 as applying to England, Wales and Scotland, so it applies across Great Britain.

Can a boiler be connected with a flexible hose?

Paragraph (2) says a flued domestic gas appliance must be connected to the gas supply system only by a permanently fixed rigid pipe.

What must an engineer check after servicing or repairing a boiler?

Paragraph (9) requires examination of the flue, the combustion air supply, the operating pressure or heat input (or combustion performance if pressure or heat input cannot reasonably be examined) and the safe operation of the appliance.

The bottom line

Regulation 26 turns safe practice into a legal duty: no unsafe installation, a rigid connection for flued appliances, an isolation valve, and four checks immediately after any work, with defects reported to the responsible person. The rule applies across Great Britain and to anyone performing gas work, and it is separate from the rules on registration. This is general information, not regulated advice on any specific installation.

Sources

This guide draws on the following primary sources, current as of 24 September 2026:

• legislation.gov.uk, “The Gas Safety (Installation and Use) Regulations 1998, regulation 26: Gas appliances—safety precautions”
• Health and Safety Executive, “Domestic gas: frequently asked questions”

Related guides

Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.