A burning smell from anything electrical is different from the other symptoms covered on this site. A tripping breaker is a device doing its job. A dead outlet is an inconvenience. A burning smell means a material that is not supposed to get hot has got hot enough to break down — and the material in question is usually the insulation whose entire purpose is keeping conductors apart.
Do this first, in this order
One. If there is visible smoke, charring, or a smell that is getting stronger while you stand there, leave and call 911. Everything below assumes you have ruled that out.
Two. Stop using whatever is nearest the smell. Unplug appliances from the outlet if you can do so without touching anything hot or discoloured. If a plug or cord is hot, leave it and turn the circuit off instead.
Three. Turn off the circuit at the panel if you know which breaker serves the area. Switching a breaker off is the one panel action that is reasonable for a homeowner — the cover stays on and you touch nothing but the breaker handle. If you do not know which breaker it is, and the smell is localised and not worsening, the main can be turned off instead.
Four. Do not remove the panel cover, take off a faceplate, or open a fixture to look. The thing you are looking for is hot and possibly live, and there is nothing you can usefully do once you find it.
Five. Get it looked at before the circuit is used again. Not after the weekend.
What you are actually smelling
Electrical components are made of thermoset plastics, PVC insulation and rubber compounds chosen because they are stable at normal operating temperatures. They emit essentially nothing until they are heated well beyond that. So an electrical smell is not an early warning — it is evidence that something has already been running much hotter than designed, probably for some time.
The heat almost always comes from resistance at a connection. A termination that has worked loose, a conductor that has oxidised, a device carrying more than it should, or an aluminum conductor on a terminal never rated for it. Current through that resistance produces heat in a confined space with nowhere to dissipate.
If it smells fishy rather than burnt
This is the detail most people do not know, and it costs them weeks. Overheating electrical plastics frequently smell fishy, or like urine or ammonia, rather than like smoke. The chemistry is unremarkable — some of the compounds released as these plastics degrade smell that way — but the consequence is significant: people smell it, conclude something has died in the wall or that there is a plumbing problem, and start looking in entirely the wrong place.
If you have an unexplained fishy smell near an outlet, a switch, a light fitting or the panel, treat it as electrical until an electrician says otherwise. It is one of the more common ways a serious overheating problem goes unaddressed for a month.
Where it usually turns out to be
At an outlet or switch. The most common location, particularly on circuits carrying heavy loads — space heaters, window air conditioners, kitchen appliances. Often combined with warmth, discolouration around the faceplate, or a plug that fits loosely. This is device and termination work, and it is usually straightforward once found.
At the panel. The most serious location. A breaker terminal that has loosened, a breaker that has failed, or a connection on the bus. A panel that smells, buzzes or is warm to the touch is not something to schedule around, and it is never something to open and inspect. Signs a panel is failing covers the other indicators.
At a light fitting. Frequently a lamp exceeding the fitting's rating, with heat accumulating in an enclosed fixture and degrading the wiring at the terminals. Recessed fittings buried in insulation that were never rated for insulation contact are a recurring version of this.
In an appliance or its cord. Sometimes the smell is the appliance rather than the house. A motor that has burnt out has a very characteristic smell. Unplug it, and if the smell goes with the appliance, that is your answer — though a cord or plug that overheated is worth taking seriously as an outlet problem too.
Things that smell similar and are not electrical
Worth ruling out, because a wasted call is annoying and unnecessary. Dust burning off heating elements the first time heat is used in autumn is extremely common and normally clears within an hour or two of running. A new fixture or appliance often smells for its first few hours as manufacturing residues burn off. Something dropped onto a heater or an oven element explains itself.
What separates these from the real thing is that they fade and do not come back. An electrical smell that recurs, persists, or is localised to one outlet, switch or fitting is not in this category — and dust burning off does not smell fishy.
Why this one does not wait
Most electrical symptoms get worse slowly and predictably. This one does not, because the mechanism accelerates itself. Resistance produces heat; heat oxidises and damages the connection; the damaged connection has more resistance; more resistance makes more heat. A connection can sit in a mildly degraded state for years and then move quickly.
The other reason is that it is happening inside a wall, ceiling or enclosure, where it is surrounded by framing, insulation and dust, and where nobody will see the next stage of it until there is smoke in the room. That is precisely the situation arc-fault protection exists to interrupt, and it is worth asking about if your house does not have it.
What an electrician does with it
Finding it is the job. That means working out which circuit is involved, then inspecting the terminations along it — at devices, at junctions and at the panel — looking for heat damage, discolouration, loose or oxidised connections and failed components. Thermal measurement under load is useful, because a connection that is merely warm at rest can be considerably hotter when the circuit is working.
The repair itself is often small: re-terminating a connection, replacing a device, replacing a breaker. What matters is that the whole circuit is checked rather than only the spot that smelled, because the same conditions that produced one bad connection frequently produced others, and because a device that has been cooked has usually damaged the conductor insulation around it too.
If the smell is present now, leave the circuit off and treat it as an emergency rather than an appointment. If it happened once and has not returned, it still needs finding — it did not resolve itself, because nothing about a loose connection improves on its own.