If you smell gas or suspect a gas leak in London, leave the property, avoid flames and electrical switches, and call the National Gas Emergency Service on 0800 111 999. Do not wait for a plumber or attempt to locate or repair the leak yourself. Follow the emergency operator’s instructions and do not re-enter until you are told it is safe.
Smell gas in London? Do this first
- Leave the affected property or area and help other people leave where it is safe to do so.
- Do not smoke, light matches or create another flame.
- Do not turn electrical switches or appliances on or off.
- Open doors and windows only when this can be done safely. Turn off gas at the meter only if it is safe and the meter is not in a cellar or basement.
- Call 0800 111 999 from a safe location and give the exact address, where the smell is strongest and whether anyone feels unwell.
Carbon monoxide: leave and obtain medical advice
Carbon monoxide has no smell. Possible symptoms include headache, dizziness, sickness, weakness, confusion, chest or muscle pain and shortness of breath. If you think carbon monoxide may be involved, stop using the suspected appliance if this can be done without delay or risk, go outside and obtain medical advice. Do not return until you have been advised that it is safe.
- Call NHS 111 if you think you may have symptoms of carbon monoxide poisoning.
- Call 999 or go to A&E for severe symptoms such as difficulty breathing, sudden confusion, loss of consciousness, marked weakness or chest pain.
- If a gas appliance may be leaking carbon monoxide, also call the National Gas Emergency Service on 0800 111 999.
Who should investigate after the emergency response?
The National Gas Emergency Service is the first contact for a suspected gas escape. After the immediate risk has been handled and re-entry is permitted, work on a gas appliance or installation must be assigned to a currently Gas Safe-registered engineer whose registration covers the relevant category. Check the official register and the engineer’s identification rather than relying only on a website badge.
Information to provide
- The full address and postcode.
- Where the smell, alarm or suspected problem was first noticed.
- Whether the smell is inside, outside or near a particular appliance.
- Whether the gas supply has been turned off and whether the smell remains.
- Whether anyone feels unwell and any access or vulnerability information the emergency responder should know.
Gas-related support after the property is safe
Only after the emergency response has dealt with the immediate risk should further diagnosis or repair be arranged. See the gas leak repair information for the service route and use the official Gas Safe Register to confirm that the assigned engineer is registered for the work required. Current availability must be confirmed directly; this guide does not promise an arrival time.
Gas emergency questions
Should I call a plumber first if I smell gas?
No. Leave the affected area and call the National Gas Emergency Service on 0800 111 999 first. Do not delay the emergency report while searching for a repair company.
Can I switch the lights off before leaving?
Do not turn electrical switches or appliances on or off when gas is suspected. Leave and follow the instructions given by the emergency operator.
What if a carbon monoxide alarm sounds?
Go outside, stop using the suspected appliance only if this can be done safely and without delay, and obtain medical advice. Call 0800 111 999 if a gas appliance may be involved. Use NHS 111 for possible symptoms and 999 for severe symptoms.
Official guidance: National Gas emergency contacts, NHS carbon monoxide advice and the Gas Safe Register.
