BoilerBuddy · gas-leak safety
If you smell gas — call 0800 111 999
If you can smell gas, follow the STOP / OPEN / LEAVE / CALL steps below. If safe and without delay, turn off gas at the meter using its control handle; do not enter a cellar or basement to reach a meter there. From outside, call 0800 111 999 (National Gas Emergency Service). Call 999 for an ambulance as well if anyone feels unwell.
How this is different from CO
Natural gas has an added odour; carbon monoxide is invisible and odourless.
Natural gas and carbon monoxide are different hazards: natural gas has an added odour, while carbon monoxide is invisible and odourless. A smell does not tell you how much gas is present. If you smell gas, act immediately and do not wait for the smell to change.
Sources: NHS carbon monoxide poisoning guidance · National Gas emergency guidance
What to do, in order
Four steps. Calm. In order.
Run these steps once, in order. If anyone feels unwell, call 0800 111 999 from outside and call 999 for an ambulance as well.
- 1
STOP — turn off gas at the meter unless it is in a cellar or basement
Turn off the appliance you were using. If you can do so safely and without delay, turn off gas at the meter using its control handle. Do not enter a cellar or basement to reach a meter there. Do not turn electrical switches on or off, look for the leak, light a match, use a mobile phone inside or smoke. If you cannot reach the meter safely and without delay, leave and continue with the next steps.
- 2
OPEN — open doors and windows on the way out
Open doors and windows as you leave the property if it costs you no extra delay. The aim is to ventilate the space and dilute any gas that has built up. Do not stop to fiddle with appliances or windows beyond what's already open — getting out cleanly is more important than chasing the perfect ventilation plan.
- 3
LEAVE — take everyone and pets out
Get everyone out of the property, including pets. Do not go back in for keys, phones, handbags or anything you can retrieve later. If anyone feels unwell, call 999 for an ambulance as well as calling 0800 111 999 from outside.
- 4
CALL — dial 0800 111 999 from outside
From outside the property, call 0800 111 999, the National Gas Emergency Service. The line is open 24/7 and free from any phone. If anyone feels unwell, call 999 for an ambulance as well. The emergency service will guide the next steps and arrange for the property to be made safe; use /find-engineer or the official Gas Safe Register to book a registered engineer once it is confirmed clear.
What NOT to do
Don't do these — they're ignition risks first, and they're very easy to do by habit.
Every one of these is on the 'do not' list because gas at any airborne concentration above about 5% in air can ignite from a small spark or naked flame. The list applies whether you can smell anything or not — the smell is only a hint, not a guide to how much gas is in the room.
- 1
Don't turn any electrical switches on or off — the spark can ignite leaked gas.
- 2
Don't light a match, lighter or any naked flame — even a candle.
- 3
Don't use a mobile phone inside the property — wait until you're outside.
- 4
Don't try to find or fix the leak yourself — that's registered-engineer territory, by law.
- 5
Don't re-enter the property until a Gas Safe registered engineer has cleared it.
If in doubt, call 0800 111 999 from outside — the call is free from any phone and the line is open 24/7. If anyone feels unwell, call 999 for an ambulance as well.
If nobody is in immediate danger
Back to the triage flow for non-emergency symptoms.
The triage flow is for non-emergency symptoms such as the boiler that will not relight, pressure that keeps dropping or error codes on the display. Tell BoilerBuddy what your boiler is doing and it will walk you through safe-at-home checks, then route you to a Gas Safe registered engineer if that is the right answer.
FAQ
The four questions this page raises.
From the same safety pair
The related pages and the engineer line alongside this one.
Safety
Carbon monoxide safety
The paired page for invisible, odourless CO — symptoms to look out for, yellow-flame meaning, and the stop / leave / call sequence if a CO alarm sounds.
carbon monoxide safety →Emergency
Emergency safety guide
STOP / LEAVE / CALL scroller for any of the three broad emergency scenarios — gas smell, CO alarm sounding, repeated lockouts — with tap-to-call numbers.
emergency safety guide →Engineer
Find a Gas Safe engineer
UK-wide directory of registered engineers — what the Gas Safe Register is, why it matters, and how to use it to book a visit near you.
find a gas safe engineer →Triage
Open the triage flow
For the non-emergency follow-up — boiler that won't relight, pressure that keeps dropping, fault codes on the display — start the triage flow and tell BoilerBuddy what's happening.
open the triage flow →