In brief
Most electrical fires start not with a sudden short circuit but with a loose connection heating up for weeks, an extension lead loaded beyond its capacity, or a panel full of dust. The annual periodic inspection shows that the installation complies; heating is caught by thermal imaging surveys carried out under load and by regular site observation. Teach employees hands-on to cut the power first in an electrical fire and to use the right extinguisher.
How do electrical fires start?
Factory fire reports often say "electrical short circuit". This phrase hides the real cause of the fire, because electrical fires usually start not in a single moment but at the end of a heating process lasting weeks. To prevent them, you need to recognise these processes:
- Loose or oxidised connections. Looseness in a terminal, switch or cable lug increases contact resistance. As current flows, the connection point heats up; as it heats up it oxidises, and the resistance increases further. This cycle can reach a temperature that ignites the insulation and surrounding plastic.
- Overload. When a cable or socket carries more current than its cross-section can handle, it heats up along its whole length. A fuse not chosen to match the cable cross-section allows this heating to continue unnoticed.
- Insulation damage. Insulation that is crushed, bent, damaged by rodents or hardened by heat leads to leakage current and arcing.
- Dust and moisture. Conductive or combustible dust building up inside a panel creates surface leakage and arcing when combined with moisture. Wood shavings, flour, textile fibres and plastic dust are particularly risky in this respect.
- Heat unable to dissipate. A cable reel used while coiled, a cable run under a carpet, or a group of sockets with material piled on top keeps the heat in.
Annex 1 of the Regulation on Health and Safety Measures for Workplace Buildings and Premises requires the electrical installation to be installed so as not to create a fire or explosion hazard, its maintenance, repair and inspection to be ensured, and the TS HD 60364-4-43 standard to be taken into account in tests. The checks below are what this general provision means on site.
Electrical panel fires: what to look for inside a panel
An electrical panel fire usually starts inside the panel, at a connection point out of sight, and by the time the door is opened it is often too late. Split panel checks into two:
Observation anyone can do with the door closed:
- Is there a smell of burning plastic, buzzing or crackling from the panel?
- Is there blackening or discolouration on the door or ventilation grille?
- Is the panel door closed, locked and the space in front clear?
- Is the panel protected from moisture and water splashes?
Checks with the door open, done only by an authorised electrician:
- Discolouration and traces of melted insulation on terminals and connections.
- Dust build-up inside the panel; cleaning by a suitable method in a panel that has been isolated and locked.
- Fuse and breaker ratings matching cable cross-sections.
- Combustible material stored inside the panel, such as labels, boxes of spare fuses or rags.
Even opening the panel door means approaching a live conductor. These checks are carried out by authorised people who know the rules for isolating and locking energy; we explained who can do electrical work in our article on who can do electrical work. For panel doors, labelling and the space in front of panels, see our article on electrical panel safety.
Extension lead hazards and socket arrangements
Extension lead hazards turn up in every workplace, from offices to production areas. The problem is not that extension leads exist but that a temporary solution becomes permanent.
| What is seen on site | Why is it dangerous? | What should be done? |
|---|---|---|
| Extension plugged into extension, multi-socket strips daisy-chained | The total load falls on the first socket and cable; the more connections, the higher the risk of looseness | A fixed socket circuit is installed; daisy-chaining is banned |
| Cable reel used at high power without being fully unwound | A coiled cable cannot dissipate heat; reels carry different power limits for coiled and unwound use | The reel is fully unwound and the limit on the label is checked |
| Heater, kettle or compressor connected to an extension | High-power devices overload thin cables | High-power devices are connected directly to a suitable fixed socket |
| Cable runs under carpets, through door gaps or across forklift routes | Crushing and heat build-up damage the insulation | The cable route is changed; trunking or a cable bridge is used |
| Loose plug, blackened socket, joint wrapped in tape | Contact resistance and exposed conductors | The equipment is withdrawn from use and replaced |
| Chargers left plugged in after hours, on top of combustible material | Unsupervised heating | A charging area is designated and kept away from combustible material |
Set a simple rule: every extension lead left permanently plugged in on the production floor points to a missing fixed socket. Count these leads on site rounds and write the need for fixed installation into the action list.
Overload fires: matching fuse and cable cross-section
The most common source of overload fire risk is the electrical installation staying the same while the business grows. A new machine, an extra compressor or heaters added in winter push existing circuits beyond their capacity. When a fuse starts blowing frequently, the most dangerous thing to do is replace it with a higher-rated one: the cable can then heat up to a point where the fuse will not protect it.
Follow these steps:
- Record load changes. When a new machine or department is added, no connection is made until the electrical lead has assessed the supplying circuit and panel.
- Do not change fuse ratings. The cause of the blown fuse is found; the rating is not increased.
- Compare with the design. The installation design is requested during the periodic inspection of the indoor electrical installation; for an installation without a design, the employer must have one prepared. The design shows how much load each circuit can carry.
- Do not defeat residual current protection. Main and sub-distribution panels should have residual current devices that respect the principle of selectivity. Bridging a device that trips frequently hides both shock and fire risk. For earthing and device tests, see our article on earthing and residual current devices.
How is a thermal imaging panel inspection done?
The annual periodic inspection shows whether the installation complies, based on values measured on that day. One effective way of catching heating that develops over weeks is a thermal imaging panel inspection. A thermal camera turns temperature differences invisible to the eye into an image; a loose terminal appears noticeably hotter than the connections around it.
The legislation does not make thermal surveys mandatory, but they have a place in a well-designed maintenance programme. To get results from a survey:
- Survey under load. Heating is caused by current; a loose connection in a panel running idle may not appear hot. Plan the survey for hours when production is at normal load.
- Compare like with like. The connections of three phases carrying the same load should be at similar temperatures. One phase being noticeably hotter suggests a problem at that connection.
- Set the rule for opening doors. A survey done with the door open means approaching a live panel; this work is done by an authorised person with suitable protective equipment. For panels surveyed frequently, fitting an infrared inspection window to the door can be considered as an option.
- Ask for priorities in the report. The report should show, for each finding, the location, a photo, the measured temperature difference and the recommended urgency. International maintenance standards use urgency levels based on temperature difference; ask the person preparing the report to state in writing which criterion they used.
| Thermal finding | Possible cause | Action |
|---|---|---|
| A single terminal or lug noticeably hot | Loose or oxidised connection | After isolating and locking, the connection is cleaned and tightened; re-surveyed |
| One of the phases at the same load hotter than the others | Connection problem or unbalanced load | Connection check, review of load distribution |
| Whole body of a fuse or breaker hot | Overload or worn contacts | Load is measured; device replaced if necessary |
| Cable heated along its whole length | Insufficient cross-section, overload | Circuit load reduced or cross-section increased |
| Neutral conductor hotter than expected | Unbalanced load; may be a harmonic effect | Measurement and assessment by an electrical engineer |
Surveying once or twice a year, for example before the winter heating load and the summer cooling load, catches seasonal load increases. Re-surveying the same point after repair shows that the problem has really been solved.
Legal framework and annual plan
Tie your electrical fire prevention work to an annual plan:
| Frequency | Task | Who does it? |
|---|---|---|
| Daily and weekly | Observation of the space in front of panels, smells, heating, extension leads | Department supervisor, employees |
| Monthly | Residual current device test button (per manufacturer's instructions), site round | Electrical lead, OHS specialist |
| Once or twice a year | Thermal survey under load | Competent thermography practitioner |
| At least once a year | Periodic inspection of indoor electrical installation, earthing and lightning conductors | Competent person registered on EKİPNET |
| On every change | Assessment before a new machine, extra load or moving a department | Electrical lead, design author |
The 2026 basic administrative fine for failing to have periodic inspections carried out is 33,326 TL, and it is increased according to the size of the workplace and its hazard class; you can see the amounts with the OHS administrative fines tool. For how to read the non-conformities in reports, see our article on how to read a periodic inspection report, and to put inspection dates on the calendar, the OHS calendar tool.
Responding to an electrical fire: what should employees be taught?
However good prevention is, employees need to know what to do in the first minute of an electrical fire:
- Raise the alarm. The person who sees the fire raises the alarm first.
- Cut the power. If it can be reached safely, the relevant fuse or main switch is turned off. The electrical isolation points are shown in the emergency plan.
- Choose the right extinguisher. Water or foam is not used on live equipment; a carbon dioxide or dry chemical powder extinguisher is used.
- Move away from a growing fire. If smoke is thickening, the response is abandoned and evacuation begins.
For choosing extinguishers, see our article on fire extinguisher types. These things are learned through practice, not by reading. We deliver theoretical and practical fire training; employees try using an extinguisher on a controlled fire. For businesses in Bursa and the surrounding provinces, we plan the annual inspections of electrical installations, earthing and other equipment through our periodic inspection service and follow up the closure of non-conformities in the reports.
Frequently Asked Questions
Is a thermal imaging survey a legal requirement?
No. The legislation requires periodic inspection of the indoor electrical installation and earthing at least once a year; a thermal survey does not replace this inspection. However, because it catches heating that develops over time, such as loose connections, early, adding it to the maintenance programme is recommended.
Is using extension leads prohibited?
Extension leads themselves are not prohibited; they are a tool for temporary, controlled use. Leads that become permanent, are daisy-chained, supply high-power devices or are crushed create a fire risk and should be replaced with fixed installation.
Can we replace a fuse that blows frequently with a bigger one?
No. A fuse is chosen according to the cable cross-section to protect the cable against overheating. Increasing the rating allows the cable to heat up without the fuse blowing. The cause of the blowing must be found first and, if necessary, the circuit and panel redesigned.
Can water be used on a fire in an electrical panel?
No. Using water or foam on live equipment puts the person responding at risk of electric shock. The power is cut first; a carbon dioxide or dry chemical powder extinguisher is used.
Equipment inventory and an inspection calendar under the new Annex III, with inspections carried out through our solution partners, plus report and defect follow-up.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.