Smell Of Gas In The House

What's happening?

Natural gas has no smell of its own. Suppliers add a stenching agent, mercaptan, so that a leak announces itself as the familiar rotten-egg smell long before the gas reaches a concentration that could ignite. Smelling it indoors means gas is escaping somewhere between the meter and an appliance, or from an appliance that has been left on unlit. The escape may be tiny — a weeping joint on a cooker bayonet — or it may be a fractured pipe under a floor. You cannot tell which by smell, and there is no safe amount to live with. The response is the same regardless of strength: ventilate, isolate, get out, and phone the free national emergency number.

What usually causes it?

• A cooker or hob tap knocked on without lighting, letting unburnt gas into the room
• A perished or badly fitted flexible bayonet hose behind a freestanding cooker
• A weeping compression or threaded joint on internal gas pipework, often after building work
• Corrosion on an old buried or boxed-in steel gas pipe run
• A meter union or governor leaking at the meter box itself
• A gas fire, back boiler or water heater with a failed valve seat that passes gas when off
• An appliance disconnected during a kitchen refit and never properly capped

When should you call a gas engineer?

The emergency service attends first and will isolate or cap the escape, but it does not repair your pipework or appliances. Once the property is made safe you need a Gas Safe registered engineer to trace the fault, repair or replace what failed, tightness-test the installation and recommission every appliance. Book that as soon as the emergency visit is finished — the house is likely to have no gas, so no heating, hot water or cooking, until it happens.

What will the gas engineer actually do?

• Carry out a tightness test on the whole installation from the meter to prove whether gas is still escaping and roughly how much
• Isolate section by section to narrow the escape down to a run of pipe or a specific appliance
• Expose and repair or replace the failed pipe, joint, hose or appliance component
• Re-test the installation to standard and check the meter governor and emergency control valve operate correctly
• Purge and relight every gas appliance, checking each one burns correctly before leaving
• Issue paperwork recording the fault found, the work done and the test results

If you can smell gas, in order

1. Open every door and window you pass on the way out.
2. Turn the gas off at the emergency control valve beside the meter.
3. Do not touch any electrical switch, doorbell or entryphone, and put nothing alight.
4. Leave the building with everyone in it.
5. From outside, ring the National Gas Emergency Service on 0800 111 999.
6. Stay out until the emergency engineer says the property is safe.