Burning smell from the fuse box — what should I do?

A burning smell from an electrical installation is one of the warning signs that the fire and electrical safety guides highlight most consistently. Here is how to respond, what the smell can indicate, and why the response matters.

Immediate steps

The response to a burning smell from a fuse box depends on what you can see and smell:

1. Look and listen. Is there visible smoke coming from the board or the wall near it? Is there a crackling or buzzing sound? Are there scorch marks, blackening, or melted plastic visible around the unit, nearby sockets, or cables?
2. If there is any smoke, visible fire, or significant heat: do not approach the board. Leave the property, alert anyone else inside, call 999, and do not re-enter until the fire service confirms it is safe. Electrical fires can develop rapidly inside wall cavities and cable runs.
3. If there are no visible flames or smoke: if you can safely reach the main isolator on the board, switch it off. This removes power from the circuits (though the cables from the meter to the main switch remain live — do not touch these). Once the main isolator is off, do not switch it back on. Leave the board isolated and call a registered electrician.
4. Do not investigate the inside of the board yourself. Even with the main isolator switched off, the incoming cables from the meter are live at mains voltage. Opening a consumer unit cover requires competence and appropriate precautions that a general householder does not have.

What causes a burning smell from a consumer unit

A burning smell from a fuse box or consumer unit typically comes from one of the following sources:

• Arcing from a loose connection: the most common and most serious cause. A connection inside the board that has worked loose — at a circuit breaker terminal, the neutral bar, the earth bar, or on the incoming tails — creates an intermittent electrical contact. When current jumps across the air gap between a loose conductor and its terminal, it arcs. Arcing generates intense heat, carbonises surrounding insulation and enclosure material, and smells distinctively of burning plastic, ozone, or char. Left unaddressed, arcing connections cause fires.
• Overheating device: a circuit breaker or RCD that has operated under high fault current — or a device that is nearing the end of its service life and runs hot — can generate heat sufficient to be smelled outside the enclosure.
• Fault in a connected circuit: occasionally the burning smell originates not at the board itself but at a fault point elsewhere on a circuit — a loose connection at a socket, a junction box, or a light fitting — whose heat and smoke is travelling back through the cable to be noticed near the board. The location can be misleading.
• Active fire in wiring: in the worst case, insulation fire has started in cable runs inside the wall or ceiling, and the smell is reaching the board because cables converge there. This is the scenario that most requires emergency service response.

Scorch marks and heat damage — what they indicate

Scorch marks on or around the consumer unit, blackening of the enclosure, melted or discoloured plastic on the unit's cover, circuit breaker carriers, or adjacent sockets are physical evidence that overheating has already occurred. Scorch marks do not go away — they are a permanent record of a heat event that has already happened inside or around the unit.

If you discover scorch marks around a consumer unit:

• Treat it as an urgent matter, even if there is no current burning smell.
• Do not use the board until it has been inspected by a registered electrician.
• Scorch marks inside a consumer unit, on breaker faces, or on the busbar enclosure are typically evidence of arcing or a fault that operated under high current — both require investigation and most likely replacement of the affected devices or the board itself.

Scorch marks on the outside of the board's cover — where cables enter the unit, or on the wall behind — can indicate that heat has been generated at a cable entry point or within the wall, which is a more complex fault to investigate.

Response guide by observation severity. Sources: Electrical Safety First; fire service guidance.

After the electrician has inspected

Depending on what the inspection finds, the outcome is typically one of:

• Loose connection remedied: if a loose terminal is identified and is the isolated cause, the connection is re-made correctly, tested, and the board returned to service. This is the best-case outcome and is entirely possible if the problem was caught early.
• Device replacement: if a circuit breaker, RCD or RCBO has been damaged by the heat event and is no longer operating within specification, it is replaced. On a modern board, individual devices can often be replaced without replacing the whole unit.
• Consumer unit replacement: if the board itself has been damaged — the busbar, the enclosure, or multiple devices — or if the board is older and the fault has exposed wider issues with its condition, a replacement may be the practical recommendation. An older plastic or wooden-backed board that has had an arcing event inside it should normally be replaced rather than repaired.
• Wiring investigation: if the source of the heat is traced to a fault point in the fixed wiring rather than the board itself, that section of wiring needs to be found, opened up and repaired — which is a more involved job.

In all cases, the board should not be returned to full use until the registered electrician is satisfied it is safe and has updated the certification accordingly.

Frequently asked questions

Sources & further reading

• Electrical Safety First — electrical fires
• Electrical Safety First — signs of electrical danger in the home
• London Fire Brigade — electrical safety at home

Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and installation. They are guidance, not a quotation.