How to Handle a Gas Leak on Site

Why Every Gas Engineer Needs a Drilled-In Procedure

You might go years without hitting a serious gas leak on site. But when it happens, the difference between a controlled shutdown and a dangerous situation comes down to whether you have a clear procedure committed to memory. Fumbling through the steps under pressure isn't an option when you're dealing with natural gas or LPG.

This guide covers the exact sequence you should follow, from the moment you detect a leak through to your reporting obligations and what you need to communicate to the customer. It's based on the requirements in IGEM/UP/1B (Tightness Testing and Direct Purge), BS 6891 (Installation of Low Pressure Gas Pipework), and current Gas Safe Register technical bulletins.

Step 1: Immediate Actions at the Point of Detection

The moment you detect a gas leak — whether by smell, your gas detector alarming, or a failed tightness test — your first priority is preventing ignition and protecting life.

1. Do not operate any electrical switches. This includes light switches, doorbells, fans, and your own power tools. Don't plug anything in or unplug anything. An electrical arc is all it takes.
2. Extinguish all naked flames immediately, including pilot lights on other appliances if safe to do so.
3. Turn off the gas supply at the emergency control valve (ECV). On a standard domestic meter, this is the handle on the inlet side of the meter — turn it so the handle is perpendicular to the pipe (a quarter turn).
4. Ventilate the property. Open all doors and windows. Do not use mechanical ventilation or extractor fans — the motors can cause sparks.
5. Evacuate if necessary. If the gas concentration is high, if anyone is showing symptoms of exposure, or if you cannot isolate the supply, get everyone out of the property and to a safe distance.

Step 2: Assess the Source and Severity

Once the gas is isolated and the area is ventilated, you need to work out what you're dealing with. There's a significant difference between a leak you've caused during your own work and a pre-existing leak you've discovered.

Leak Caused During Your Work

If the leak is the result of something you've done — a joint you haven't finished, a fitting that's failed during installation, or a pipe you've accidentally damaged — the situation is more straightforward. You have direct control over the repair. Once the gas is off and the area is safe:

• Identify the exact point of the leak
• Make the repair before re-establishing the gas supply
• Conduct a full tightness test to IGEM/UP/1B before turning the gas back on
• Purge and relight all appliances

Pre-Existing Leak You've Discovered

This is where it gets more involved. If you've found a gas leak that was already present — perhaps during a routine service or while investigating another issue — you have specific obligations under Gas Safe registration.

Under the Gas Industry Unsafe Situations Procedure (GIUSP), you must classify the situation:

• Immediately Dangerous (ID): There's an immediate risk to life. The gas supply must be disconnected and the situation made safe before you leave site. You must issue a Gas Safe Warning Notice and advise the customer not to use the installation until a repair is made.
• At Risk (AR): The situation is not immediately life-threatening but could become dangerous. You should advise the customer of the risk, issue a Warning Notice, and recommend urgent repair. If the customer agrees, you can cap off and isolate. If they refuse, you must still record the situation.
• Not to Current Standards (NCS): The installation doesn't meet current standards but isn't an immediate safety risk. Advise the customer and record it, but there's no obligation to disconnect.

A detectable gas leak will almost always fall into the ID or AR category. Don't be tempted to downgrade it.

Step 3: Tightness Testing After a Leak

Before any gas supply is re-established, you must carry out a tightness test in accordance with IGEM/UP/1B Edition 3. The key points to remember:

• The test medium is air or the gas supply itself, using a suitable manometer or pressure gauge
• For installations operating at pressures up to 75 mbar, the standard test pressure is 20 mbar
• Allow a 1-minute stabilisation period, then monitor for 2 minutes on domestic-sized installations
• There should be no perceptible drop in pressure during the 2-minute test period
• If the test fails, you must locate and repair the leak, then retest

Make sure your gauge is properly calibrated — an inaccurate gauge can give you a false pass, which puts lives at risk and your registration on the line.

Step 4: RIDDOR Reporting

Under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013 (RIDDOR), certain gas-related incidents must be reported to the Health and Safety Executive (HSE).

As a Gas Safe registered engineer, you are legally required to report any gas fitting or gas supply issue that you consider to be dangerous enough to warrant immediate disconnection. Specifically, RIDDOR regulation 6(2) requires a registered gas engineer to report:

• Any gas appliance, fitting, or flue that is considered dangerous on the basis that it could cause death, loss of consciousness, or hospital admission
• Any inadequate gas installation that could lead to a gas leak of a dangerous nature

Reports must be submitted to the HSE, and this can be done online via the HSE RIDDOR reporting portal. You should submit the report within 14 days of the incident or discovery.

Step 5: Communicating with the Customer

How you handle the conversation with the customer matters. People get anxious about gas leaks, and rightly so. Here's how to handle it professionally:

• Be clear and factual. Explain what you've found, what you've done to make it safe, and what happens next. Avoid downplaying or dramatising the situation.
• Explain the Warning Notice. If you're issuing one, explain what it means. Make clear that this is a formal safety record, not a scare tactic.
• Give them options. If you can carry out the repair, quote for the work. If it's beyond your scope, recommend they contact another Gas Safe registered engineer. Never pressure a customer into immediate work on the back of a safety scare.
• Leave a paper trail. Whether it's a Warning Notice, a written summary, or a digital record through CertBox, make sure the customer has something in writing confirming what was found, what was done, and what's recommended.

Step 6: Recording and Documentation

Thorough documentation protects you professionally and helps ensure nothing falls through the cracks. For every gas leak incident, you should record:

• Date, time, and location of the discovery
• Description of the leak — location on the installation, estimated severity
• Actions taken — isolation, ventilation, evacuation if applicable
• Tightness test results (before and after any repair)
• GIUSP classification (ID, AR, or NCS)
• Warning Notice details if issued
• RIDDOR report reference number if applicable
• Customer communication — what was discussed and agreed

Key Regulations and References

Keep these references to hand — they're the documents that underpin your obligations:

• IGEM/UP/1B Edition 3 — Tightness Testing and Direct Purge of Small Natural Gas Installations
• BS 6891:2015+A2:2019 — Installation and Maintenance of Low Pressure Gas Pipework
• GIUSP (Gas Industry Unsafe Situations Procedure) — Classification and management of unsafe situations
• RIDDOR 2013 — Reporting of Injuries, Diseases and Dangerous Occurrences Regulations
• Gas Safety (Installation and Use) Regulations 1998 — The overarching legal framework for gas work in the UK

None of this is optional. Every step — from isolation to reporting — is there because the alternative is someone getting hurt. Drill the procedure until it's second nature, document everything, and never cut corners when gas is involved.

Published 2026-03-10. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the relevant standards and consult qualified professionals for definitive requirements.