Burning smell from a socket: act now

Of all the electrical calls we take, this is the one where we are least interested in you trying anything. A socket, switch or fused spur that smells of burning, fish or hot plastic, or is warm or discoloured to the touch, is arcing or overheating behind the faceplate. It will not get better on its own, and the next stage is a fire inside the wall. This guide is short on advice because there is not much advice to give beyond: stop using it and call us.

What the smell means

A burnt-toast smell is arcing, where current is jumping across a loose or corroded connection and making tiny sparks. Both mean a connection somewhere behind that faceplate is loose, overloaded or damaged, and heat is building. Brown or black marks around the pin holes, a faceplate that has softened or distorted, or a crackling sound are later signs of the same thing.

Sometimes the smell comes from the plug or appliance rather than the socket. That is also a fault and also needs attention, but it is less urgent for the house.

What to do now

Stop using the socket. If there is a plug in it and the plug is cool to the touch, unplug it. If the plug is hot, or the socket itself is hot, do not touch it with your hand. Switch off the socket at its own switch if it has one and you can do so without touching the faceplate. Then leave it alone.

Do not plug anything else into it to test it. Do not remove the faceplate to look. Do not spray anything into it. Do not tape over it and carry on.

If you can see smoke, flames, or the wall around the socket is hot, get everyone out and call 999. Do not use water on an electrical fire. The socket can be dealt with after the fire brigade has been.

If you know which circuit breaker serves that socket and you can reach the consumer unit safely, switching that breaker off removes the risk until we arrive. If you are not sure, or the consumer unit is unlabelled, leave it. We would rather you left a circuit live than touched something you were unsure of. Do not open the consumer unit cover under any circumstances.

Why it happens

The usual causes are a loose terminal screw, often on a socket that was fitted or replaced in a hurry; an overloaded socket, typically from a multi-way adaptor running a heater and a tumble dryer; a damaged cable behind the wall; corrosion in a damp location such as a kitchen or a conservatory; and simple age. In the pre-war houses across south Manchester we still find original rubber-insulated cable at the back of sockets, and it becomes brittle and crumbles.

Heaters are the single biggest culprit. A portable heater draws a lot of current continuously, and a socket that copes with a lamp for twenty years can fail in a week under a heater.

What we do

We isolate the circuit, remove the accessory and inspect the terminals and the cable behind it. Often the cable ends are charred and need cutting back to sound copper; sometimes the back box or the cable itself has to be replaced. We fit a new accessory, test the circuit for insulation and earth continuity, and check the other sockets on the same circuit, because a loose connection in one is often a sign the whole circuit was fitted the same way.

We treat this as an emergency at any hour.

Afterwards

A socket that has overheated once is a reason to look at the rest of the installation, especially if the property is more than thirty years old or has never had an inspection. And whatever the age of the house, plug heaters directly into a wall socket, never into an extension lead.