A class E fire is a fire involving live, electrically energised equipment including wiring, switchboards, motors, computers, UPS units, and servers where the active electrical supply is still on. That live supply creates an electrocution risk that makes class E fires uniquely dangerous. Water and foam conduct electricity and can kill the person trying to fight the fire. Only CO₂ fire extinguisher and dry powder extinguishers with verified dielectric safety ratings are safe to use on a class E fire.
Class E classification applies only while the equipment is energised. Once the power is confirmed off, the fire is reclassified by what is burning, usually class A fire for plastics and insulation and could it different classes of fire.
| Question | Answer |
|---|---|
| What is a Class E Fire? | A fire involving live electrical equipment. |
| Correct Extinguisher | CO₂ (primary), DCP (secondary), or a clean agent system for server rooms and sensitive electronics. |
| Never Use | Water, foam, or wet chemical extinguishers, as they can conduct electricity and increase risk. |
| Indian Standard | IS 15683:2018 (BIS) classifies these as Class E fires. |
| US Standard | NFPA 10 refers to the same hazard as a Class C fire. |
| European Standard | EN 2 / EN 3 does not define a separate electrical fire class. Extinguishers are marked with their tested electrical safety voltage. |
| First Action | De-energise the equipment if it is safe to do so. If power cannot be isolated, use a CO₂ extinguisher from approximately 1 metre away. |
A UPS unit in a commercial office had been running with a loose terminal for six weeks. The loose connection was arcing, tiny, brief sparks that left a faint burning smell. The maintenance team assumed the UPS was running warm. One evening, the arc ignited the terminal insulation and the fire spread to the cable tray above. The first person to respond grabbed the nearest red extinguisher, a water unit. The moment the water stream hit the live 230V output, the shock threw them across the room.
The difference between that water extinguisher and a CO₂ unit is the difference between a fire response and a fatality. That is what class E fire safety comes down to.
What is a class E fire?
A class E fire is a fire involving electrically energised equipment such as wiring, control panels, motors, computers, and servers where the active electrical supply creates an electrocution risk. That risk rules out water, foam, or any conductive extinguishing agent.
A class E fire is a fire involving electrically energised equipment where the live electrical supply creates an electrocution hazard that prevents the use of water, foam, or any conductive extinguishing agent.
One fact separates class E from every other fire class. The classification applies only while the equipment is energised. Cut the power and confirm it is off, and the fire becomes a class A fire burning plastic and insulation or a class B fire if transformer oil is involved. The electrical hazard disappears with the power.
How electrical fires start: three ignition mechanisms explained
Mechanism 1: Overload and sustained resistive heating (Joule’s law)
Current flowing through a conductor produces heat. Joule’s law states that heat output equals I²R, current squared multiplied by resistance. Double the current and heat output quadruples.
When too much current flows through an undersized cable from an overloaded extension lead, too many appliances on one circuit, or wiring that was never rated for the load, heat builds faster than the cable can shed it. The insulation reaches its temperature limit, degrades, and ignites.
This process is slow. The cable may run hot for hours or days before ignition. There is no arc, no spark, no warning sound. Just sustained heat until something burns.
Mechanism 2: Arc fault, the invisible fire starter
An arc fault is an unintended electrical discharge between two conductors or between a conductor and earth. The plasma arc it produces exceeds 3,000°C, hotter than the surface of the sun. It ignites anything within reach including cable insulation, timber framing, and dust on cable trays.
Arc faults happen at loose connections, corroded terminals, damaged insulation, and pinched cables. The most dangerous type is a series arc fault, a recurring, brief arc at a damaged point. Standard circuit breakers (MCBs) do not detect series arc faults because the average current may be within normal range. The breaker sees nothing wrong. The arc continues.
Mechanism 3: Electrical tracking on contaminated insulation
Electrical tracking explains many electrical panel fires that appear to start for no reason.
When moisture or conductive contamination such as dust, salt, or chemical residue deposits on an insulating surface, a small leakage current begins flowing across that surface. The current heats the path. Heat carbonises the insulation. Carbon is conductive, so more current flows, more heat is generated, and the carbonised path extends further.
Over weeks or months this becomes a permanent conductive channel that sustains arcing and eventually ignites the surrounding material. It is entirely invisible from outside the enclosure until fire or smoke appears.
Why class E fires are uniquely dangerous
The electrocution hazard: why water kills
Water conducts electricity. At 1,000V, a water stream can deliver a fatal shock to the operator at up to 1 metre from the point of contact. At higher voltages such as industrial switchgear and substation equipment, the safe standoff distance is far greater.
A class E fire fought with a water extinguisher is immediately life threatening to the firefighter. Water is not just ineffective on a class E fire. It is a direct threat to the person holding it.
Toxic smoke from burning electrical materials
Electrical fire smoke is not generic smoke. When electrical equipment burns, specific toxic gases form depending on what is on fire:
• PVC cable insulation produces hydrogen chloride (HCl)
• Polycarbonate and ABS plastic housings produce hydrogen cyanide (HCN), benzene, and styrene
• Printed circuit boards (PCBs) produce hydrogen bromide (HBr) and potentially dioxins
• Transformer oil produces acrolein and polycyclic aromatic hydrocarbons
• Rubber insulation produces sulphur dioxide (SO₂)
The combination of HCl and HCN reaches toxic concentrations quickly in an enclosed room.
The speed of spread through cable infrastructure
An electrical fire can travel along cable trays, trunking, and conduit at significant speed. A fire starting at a distribution board can reach every floor connected to that board through the vertical cable risers within minutes.
The science of why CO₂ is safe on live electrical equipment
Every fire guide says “use CO₂ on electrical fires.” Very few explain why. Understanding the reason also explains why certain other agents are dangerous.
What dielectric strength means
Dielectric strength is a material’s ability to resist electrical conduction. High dielectric strength means current cannot pass through it. Low dielectric strength means it conducts electricity.
This single property determines whether an extinguishing agent is safe or dangerous on a live class E fire.
Why water is dangerous on live equipment
Water at firefighting concentrations has essentially zero dielectric strength. It conducts electricity directly from the energised equipment, through the water stream, to the person holding the hose. At 1,000V, that path can deliver a fatal current at up to 1 metre from contact. At higher voltages, the danger radius grows significantly.
Why CO₂ is safe
CO₂ discharged from a fire extinguisher is a dry gas. Dry gas does not conduct electricity. There is no liquid stream and no conductive path from the energised equipment to the operator.
This is why CO₂ is the primary agent for class E fires, not because it is universally safe around electronics, but because it creates no conduction path between live equipment and the firefighter. CO₂ extinguishers are tested safe at a minimum 1 metre standoff from energised equipment. Never touch the horn to live equipment.
Why DCP is effective but damaging
Dry chemical powder (DCP/ABC) also has high dielectric strength in its dry discharged form. It does not conduct electricity and is safe for the operator to use on class E fires.
The problem is what happens after discharge. DCP is hygroscopic. It absorbs moisture from the air. Once it absorbs moisture, it becomes mildly conductive. On sensitive electronics, that powder plus moisture creates new conductive paths inside enclosures, on PCBs, and across terminal blocks. Secondary damage from DCP on electronics routinely exceeds the damage from the fire itself.
Use CO₂ on class E fires involving computers, servers, control panels, and precision equipment.
The de energise decision: when to cut power first and when you cannot
When de energising is the first action
In most class E fire scenarios such as residential wiring fires, office appliance fires, and standard industrial equipment, the isolation point is accessible and de energising takes seconds.
Follow this sequence:
- Alert others and begin evacuation.
- Isolate at the nearest distribution board, MCB, or main switch.
- Confirm isolation with a voltage tester if trained and equipped.
- Fight the now de energised fire. It is now classified by what is burning, typically class A for insulation and plastics.
- Call emergency services regardless of how small the fire appears.
Once power is confirmed off, the primary class E hazard is gone. A broader range of extinguishers becomes available.
When de energising is not immediately possible
Four scenarios prevent immediate isolation:
- Cannot locate the isolation point, such as an unfamiliar building, no circuit labelling, or a locked distribution board.
- Isolation point is inside the fire zone and the panel itself is on fire.
- High voltage or specialist access is required, such as substation equipment, high voltage switchgear, or utility infrastructure.
- The system cannot be shut down, such as hospital life support, data centre systems with no failover, or critical industrial processes.
In these cases, CO₂ or DCP must be used at a safe standoff distance. Do not use water, foam, or wet chemical while energisation status is uncertain.
The fundamental rule
Treat every electrical fire as live until a qualified person confirms it is de energised.
The visual appearance of fire does not confirm whether the system is still energised. Equipment that looks destroyed may still be live.
Class E extinguishers: CO₂, DCP, and clean agents compared
CO₂ fire extinguisher: primary choice for class E fires
CO₂ suppresses fire by displacing oxygen below the level needed for combustion. It leaves no residue. Equipment can be inspected and returned to service immediately after discharge. It is the preferred agent for class E fires involving electronics, server racks, UPS units, and control panels.
Limitations to know before using CO₂:
• Discharge temperature is -78°C. The horn reaches extreme cold during discharge. Never grip it bare handed. Frost burns occur immediately. Always hold the insulated handle only.
• In an enclosed space such as an electrical cupboard, a small UPS room, or a server room, CO₂ discharge rapidly reduces oxygen. At 7% CO₂ in air, the atmosphere is immediately dangerous and unconsciousness follows quickly. Evacuate the room before or during discharge. Do not re enter without ventilation.
• CO₂ dissipates quickly in ventilated spaces. If the electrical fault has not been isolated, re ignition risk is real.
DCP / ABC dry powder: effective but with a damage trade off
DCP is highly effective on class E fires and interrupts the chemical chain reaction of combustion.
Use DCP when the equipment is already destroyed and speed matters more than salvage, such as large industrial electrical fires, switchgear fully alight, or cable bundles on fire.
Do not use DCP on computers, servers, UPS units, or any precision electronics. The hygroscopic residue causes secondary equipment damage that exceeds the fire damage.
Clean agent extinguishers: for high value electrical environments
FM200 (HFC 227ea) and Novec 1230 (FK 5 1 12) are the correct agents for data centres, server rooms, and occupied electrical spaces.
Both suppress fire by interrupting the chemical chain reaction, not by displacing oxygen.
This makes them:
• Safe for occupied spaces because discharge does not reduce breathable air to dangerous levels
• Zero residue because equipment returns to service immediately after discharge
• Electrically non conductive and safe on live class E fires
• Free of cold discharge damage with no -78°C thermal shock to storage media
CO₂ is adequate for unoccupied server rooms where evacuation can be confirmed before discharge. For occupied or partially occupied server environments, FM200 or Novec 1230 are the right choice.
| Agent | Why It Must Never Be Used |
|---|---|
| Water | Conducts electricity and creates a serious electrocution risk when used on live electrical equipment. |
| Foam | Contains water and presents the same electrical shock hazard on energised equipment. |
| Wet Chemical | Water-based agent designed for Class F cooking oil fires and unsafe for Class E electrical fires. |
| Standard Water Mist | Not suitable unless specifically dielectrically tested and clearly labelled for electrical fire use. |
“Class E fire”: why this classification exists in India but not in Europe
This is one of the most practically important facts for Indian safety professionals and one that many guides do not explain clearly.
India and Australia: Class E is explicit
Under Indian Standard IS 15683:2018 (BIS) and Australian Standard AS/NZS 1841, Class E is a defined fire class for fires involving live electrical equipment. Extinguishers are rated for class E use and labelled accordingly.
Europe: no Class E exists
Under European Standard EN 2 / EN 3, there is no Class E. European standards do not classify electrical fires as a separate class. Their reasoning is that electricity is an ignition source, not a fuel. Once equipment is de energised, the fire becomes a class A, B, or C fire depending on what is burning.
European extinguishers carry a label stating whether they are safe for use on live electrical equipment and at what test voltage, typically 1,000V or 35,000V.
USA: Class C means electrical fires
Under NFPA 10, there is no Class E. The US uses Class C for fires involving energised electrical equipment, the same letter India uses for flammable gas fires.
Why this matters
An Indian safety officer reading a US safety manual will see “Class C fire” used for electrical fires. The same officer reading a European manual will find no class letter at all. Neither conflicts with Indian practice, but the naming difference causes dangerous confusion for anyone who reads across standards.
| Standard | Region | Electrical Fire Class | Flammable Gas Fire Class |
|---|---|---|---|
| IS 15683:2018 (BIS) | India | Class E | Class C |
| AS/NZS 1841 | Australia | Class E | Class C |
| EN 2 / EN 3 | Europe | Not classified separately (label states safe voltage) | Class C |
| NFPA 10 | USA | Class C | Part of Class B |
Where class E fires most commonly occur
Residential settings
Overloaded extension leads and daisy chained multi socket adapters are the most common residential class E fire source. Older buildings built before 1980 may have aluminium wiring or degraded PVC insulation at the end of its service life. Faulty appliance power leads and EV chargers on undersized domestic circuits are a growing cause.
Commercial offices
Server rooms and UPS rooms carry the highest risk. These areas run at high electrical density 24 hours a day. Distribution boards expanded over time to accommodate office growth are consistently overloaded. Old fluorescent lighting ballasts are a secondary risk in older buildings.
Industrial facilities
Motor control centres (MCCs) are the primary industrial class E fire risk. Motor starting loads create high current events that stress connections and terminals. Industrial UPS systems, switchgear in manufacturing plants, and CNC machine electrical panels are all high risk class E environments.
Data centres and telecommunications
Electrical fires represent over 50% of all large fire incidents in data centres globally. The concentrated electrical density of these facilities combined with continuous 24/7 operation creates persistent arc fault and overload risk.
UPS battery thermal events, cable management failures, and cooling system electrical faults are the leading causes.
The Indian industrial context
India’s rapid industrial growth means significant quantities of older, underspecified electrical infrastructure operating at or beyond original design capacity. Factories, textile mills, pharmaceutical plants, IT parks, and cold storage facilities all operate with motor heavy systems that need regular thermal inspection.
State fire services data year after year lists electrical short circuits as the single largest cause of fire incidents in India.
Globally, electrical fires account for up to 30% of all fires and exceed 50% of all large fires, making class E fire prevention one of the highest return investments a facility can make.
Preventing class E fires: protection technologies and practical steps
Circuit protection technologies
Most buildings rely on MCBs (miniature circuit breakers). MCBs protect against overloads and short circuits. They trip when current exceeds rated capacity. They do not detect arc faults.
RCDs and RCCBs (Residual Current Circuit Breakers) detect earth leakage, current escaping to earth through damaged insulation or an unintended path. They trip within 30 milliseconds on a 30mA fault, fast enough to prevent electrocution in most cases.
They reduce class E fire risk from earth fault scenarios but do not protect against series arc faults.
AFCIs (Arc Fault Circuit Interrupters) detect the high frequency electrical signatures that arcing produces. They trip the circuit before the arc can ignite surrounding material, the one threat MCBs are blind to.
AFCIs are now mandatory in new residential construction under the US National Electrical Code. They are not yet mandatory in India but are available and increasingly used in premium construction and data centre builds.
| Protection Device | Protects Against | Does NOT Protect Against |
|---|---|---|
| MCB | Overloads, short circuits | Arc faults, earth faults |
| RCD / RCCB | Earth leakage, electrocution | Series arc faults, overloads |
| AFCI | Series and parallel arc faults | Sustained overloads (requires an MCB alongside) |
Electrical maintenance schedule
• Annual thermal imaging survey of all electrical panels and distribution boards. Thermal cameras detect high resistance connections generating heat before they reach ignition temperature.
• Visual inspection of cable insulation in areas of mechanical movement, UV exposure, or chemical presence.
• Torque testing of connections in MCCs, distribution boards, and switchgear. Loose connections are the primary arc fault cause.
• Monthly RCD test. Press the test button on every RCD in the building to confirm it is still functional.
Operational prevention steps
• Never use extension leads as permanent wiring.
• Never daisy chain multi socket adapters.
• Replace any cable with cracked, pinched, or damaged insulation immediately.
• Never add electrical load to a circuit without a qualified electrician assessing capacity first.
• Report any burning smell from electrical equipment immediately. Do not dismiss it.
• Ensure adequate ventilation in electrical equipment rooms. Heat buildup accelerates insulation degradation.
What to do after an electrical fire: the step most people skip
Even a class E fire that appears fully extinguished and small requires one more action that most people miss: a post fire electrical inspection before re energising.
Do not switch the power back on. Call a qualified electrician first.
Heat from an electrical fire travels along cable bundles. Insulation on conductors 10 metres from the visible fire zone in the same cable and through the same trunking may have softened, degraded, or melted. Re energising the circuit causes that degraded insulation to fail under load. The result is a second fire, typically more serious than the first.
Required steps after any class E fire
- Do not re energise until a qualified electrician or electrical inspector has assessed the full installation.
- Inspect beyond the visible fire zone. All circuits that fed the affected area must be checked throughout their runs.
- Remove all CO₂ condensation or DCP powder residue from electrical enclosures. Both must be cleared before power is restored or secondary tracking will start.
- Test insulation resistance on all affected circuits before re energising.
- Document the incident for insurance and regulatory reporting.
Skipping this step is a direct cause of repeat electrical fires. This is not a precaution. It is a requirement.
Class E fire vs other fire classes: comparison table
| Property | Class A | Class B | Class C | Class D | Class E |
|---|---|---|---|---|---|
| Fuel / Source | Solid combustibles | Flammable liquids | Flammable gases | Combustible metals | Electrical equipment |
| Primary Hazard | Deep-seated re-ignition | Vapour spread | Explosion | Violent agent reactions | Electrocution |
| Water | Yes | Never | No | Never | Never, lethal |
| CO₂ | No | Yes | Limited | No | Yes, primary agent |
| DCP | Yes | Yes | Yes | No | Yes, with equipment damage |
| Clean Agent | No | No | No | No | Yes, preferred for electronics |
| First Action | Contain and cool | Shut off source | Shut off gas | Use Class D agent | De-energise first |
Frequently asked questions: class E fires
Q1: What is a class E fire?
A class E fire is a fire involving live, electrically energised equipment such as wiring, switchboards, motors, computers, UPS units, and servers. The active electrical supply creates an electrocution hazard that rules out water, foam, or any conductive extinguishing agent.
Class E is defined under Indian Standard IS 15683:2018 (BIS) and Australian Standard AS/NZS 1841.
Q2: What causes a class E fire?
Class E fires are caused by three mechanisms.
First, overloaded conductors generate excess heat through Joule’s law (I²R).
Second, arc faults produce plasma discharges exceeding 3,000°C at loose connections or damaged insulation.
Third, electrical tracking creates carbonised conductive paths across insulating surfaces when moisture or contamination is present.
Loose connections, damaged insulation, and overloaded circuits are the root causes of all three.
Q3: What fire extinguisher should be used on a class E fire?
CO₂ is the primary extinguisher for class E fires. It is electrically non conductive and leaves no residue.
DCP (dry powder) is also dielectrically safe for the operator but causes secondary equipment damage from its hygroscopic residue.
Clean agents such as FM200 and Novec 1230 are preferred for server rooms and data centres.
Water, foam based fire extinguisher, and wet chemical must never be used on a class E fire.
Q4: Why should you never use water on a class E fire?
Water conducts electricity.
At 1,000V, a water stream can deliver a fatal shock to the operator at up to 1 metre from the contact point.
This creates a direct conductive path between energised equipment and the person holding the extinguisher.
Water is not just ineffective on a class E fire. It poses an immediate, fatal electrocution risk.
Q5: Why is CO₂ safe to use on live electrical equipment?
CO₂ has high dielectric strength and does not conduct electricity.
When discharged from an extinguisher, it is a dry gas with no liquid stream, so no conductive path forms between the energised equipment and the operator.
CO₂ extinguishers are tested and rated safe at a minimum 1 metre standoff from live equipment under IS and international standards.
Q6: What is the difference between CO₂ and DCP extinguishers for class E fires?
Both CO₂ and DCP are dielectrically safe. Neither conducts electricity during use.
CO₂ leaves no residue, making it the correct choice for electronics and precision equipment.
DCP leaves hygroscopic powder residue that absorbs moisture and creates secondary conductive paths inside electrical enclosures after discharge.
DCP damage to electronics routinely exceeds the original fire damage.
Q7: What is an arc fault and how does it cause electrical fires?
An arc fault is an unintended electrical discharge between two conductors or between a conductor and earth.
The plasma arc exceeds 3,000°C and instantly ignites adjacent combustibles such as insulation, timber, and dust.
Arc faults occur at loose connections, corroded terminals, and damaged cables.
Standard MCBs do not detect series arc faults because the average current may remain within normal range. The arc continues undetected until ignition.
Q8: Should you turn off the power before fighting a class E fire?
Yes, if the isolation point is safely accessible.
De energising removes the class E electrocution hazard and reclassifies the fire, allowing more extinguisher options.
If the isolation point cannot be reached, is inside the fire zone, or the system cannot be shut down, use CO₂ or DCP at a safe standoff distance.
Always treat the system as live until a qualified person confirms de energisation.
Electrical tracking occurs when moisture or conductive contamination on an insulating surface allows leakage current to flow.
That current heats the surface and causes carbonisation. Carbon is conductive, so more current flows, more heat is generated, and the carbonised path extends.
Over weeks or months this becomes a permanent conductive channel that sustains arcing and eventually ignites surrounding material.
Many switchgear and UPS panel fires are caused by this mechanism.
Q10: What is dielectric strength and why does it matter for class E fires?
Dielectric strength is a material’s ability to resist electrical conduction.
Water has near zero dielectric strength at firefighting concentrations. It conducts electricity and creates a dangerous path from live equipment to the operator.
CO₂ gas and dry powder both have high dielectric strength. They do not conduct electricity.
Dielectric strength determines whether an extinguishing agent is safe or dangerous on a class E fire.
Q11: Is there a class E fire classification in Europe?
No.
European Standard EN 2 / EN 3 does not classify electrical fires as a separate class.
European standards treat electricity as an ignition source rather than a fuel.
European extinguishers carry a label stating whether they are rated for use on live electrical equipment and at what test voltage, typically 1,000V or 35,000V.
There is no Class E letter classification.
Q12: Is class E fire in India the same as class C fire in the US?
Yes, functionally.
NFPA 10 uses “Class C” for fires involving energised electrical equipment, the same fire type that Indian Standard IS 15683:2018 classifies as “Class E.”
The fire is identical. Only the classification letter differs.
Indian safety professionals reading US content should note that “Class C” in a US document means electrical fire, not flammable gas fire.
Q13: What is the difference between class E fire (Indian/Australian) and class C fire (US NFPA)?
Both terms describe the same fire type: a fire involving energised electrical equipment.
India (IS 15683:2018) and Australia (AS/NZS 1841) call it Class E.
The US (NFPA 10) calls it Class C.
Europe (EN 2 / EN 3) assigns no letter at all.
The naming difference does not change the fire or the correct response, but it creates dangerous confusion when reading cross standard safety documents.
Q14: What clean agent extinguisher is best for a server room class E fire?
FM200 (HFC 227ea) and Novec 1230 (FK 5 1 12) are both suitable for server room class E fires.
Both suppress fire by interrupting the chemical chain reaction rather than displacing oxygen, making them safe for occupied spaces.
Both leave zero residue, allowing immediate return to service.
Novec 1230 has a lower global warming potential.
Automatic suppression systems using clean agents are the standard specification for data centres.
Q15: Why is CO₂ not ideal for an occupied server room?
CO₂ suppresses fire by displacing oxygen.
In an enclosed server room, a full discharge reduces oxygen concentration to dangerous levels. At 7% CO₂ in air, unconsciousness follows quickly.
Anyone present must evacuate before or immediately after discharge.
Clean agents such as FM200 and Novec 1230 suppress class E fires at concentrations that do not compromise breathable air, making them the correct choice where people may be present.
Q16: What are the dangers of CO₂ extinguisher discharge in an enclosed space?
Two specific hazards exist.
First, oxygen displacement.
CO₂ discharge in a small enclosed room rapidly reduces oxygen to dangerous levels.
At 7% CO₂ concentration, the atmosphere is immediately dangerous. Evacuate before discharge and do not re enter without ventilation.
Second, frost burn.
CO₂ discharges at -78°C and the horn reaches extreme cold instantly.
Direct contact causes immediate frost burns. Always hold the insulated handle, never the horn.
Class E fires produce specific toxic gases depending on what is burning.
• PVC cable insulation produces hydrogen chloride (HCl)
• Polycarbonate and ABS plastic housings produce hydrogen cyanide (HCN), benzene, and styrene
• Printed circuit boards produce hydrogen bromide (HBr) and potentially dioxins
• Transformer oil produces acrolein and polycyclic aromatic hydrocarbons
• Rubber insulation produces sulphur dioxide (SO₂)
The combination of HCl and HCN reaches acutely toxic concentrations quickly in enclosed spaces.
Q18: What technologies prevent class E fires at the circuit level?
Three key technologies provide circuit level protection.
MCBs protect against overloads and short circuits but not arc faults.
RCDs/RCCBs detect earth leakage and trip within 30 milliseconds on a 30mA fault, preventing electrocution and some fire scenarios.
AFCIs (Arc Fault Circuit Interrupters) detect the high frequency signatures of arcing, the one threat MCBs miss, and trip the circuit before the arc can ignite surrounding material.
Thermal imaging of panels and torque testing of connections are the essential maintenance level measures.
Q19: What should you do after a class E fire, even a small one?
Do not re energise the electrical system.
Call a qualified electrician to inspect all affected circuits, including areas beyond the visible fire zone throughout the same cable runs.
Remove all CO₂ condensation and DCP residue from enclosures before restoring power.
Test insulation resistance on all affected circuits.
Heat from a small class E fire can degrade insulation on conductors 10 metres from the visible burn zone.
Re energising without inspection causes repeat fires.
Q20: Where do class E fires most commonly occur in India?
Class E fires in India most commonly occur in:
• Residential settings with overloaded extension leads and old wiring
• Commercial server rooms and UPS rooms
• Industrial motor control centres and switchgear
• Data centre environments with high density electrical loads
India’s state fire services data consistently lists electrical short circuits as the single largest cause of fire incidents nationwide, ahead of all other fire causes.
Q21: Can foam extinguishers be used on class E fires?
No.
Foam extinguishers must never be used on class E fires.
Foam contains water as its primary component, and water conducts electricity.
Using a foam extinguisher on a live class E fire creates a direct conductive path from the energised equipment to the operator, the same electrocution risk as using a water extinguisher.
Foam is as dangerous as water on a class E fire.
Q22: What is a UPS room class E fire and how should it be handled?
A UPS room class E fire involves battery systems, inverter equipment, and power distribution in an enclosed electrical room.
UPS rooms carry elevated risk from battery thermal runaway and arc faults at terminal connections.
Handle with CO₂ or a clean agent extinguisher.
Attempt to isolate the UPS at its input isolation point if safely accessible.
Evacuate immediately before CO₂ discharge because the enclosed space creates oxygen deficient conditions.
Automatic suppression systems are strongly recommended for UPS rooms.
Q23: How does a class E fire spread through a building?
Class E fires spread through cable trays, trunking, and conduit, the pathways connecting a distribution board to every part of the building it serves.
A fire at one panel can travel via vertical cable risers to multiple floors within minutes.
Burning PVC insulation produces hydrogen chloride gas, which damages equipment far beyond the visible fire zone.
This is why class E fires in core building infrastructure are more serious than a localised class A fire of equivalent size.
Q24: What is the PASS method and does it apply to class E fires?
Yes, the PASS method applies to class E fires.
Pull the pin.
Aim at the base of the fire.
Squeeze the handle.
Sweep from side to side.
For class E fires, two additional rules apply:
• Maintain at least 1 metre standoff from energised equipment at all times.
• Evacuate the space if using CO₂ in an enclosed room.
Where safely possible, de energise the equipment before applying the PASS method because this removes the electrocution hazard entirely.
Conclusion
Class E fires are the most dangerous to respond to incorrectly, not because the fire is uncontrollable, but because the wrong extinguisher turns the firefighter into the victim.
Four things determine whether a class E fire response is safe and effective:
• The correct extinguisher
• The correct standoff distance
• The de energise decision made in the right order
• The post fire inspection step that most people skip entirely
Speciality Geochem manufactures BIS certified CO₂ fire extinguishers specifically rated for class E fires and supplied to the Indian Army, Indian Railways, and major industrial facilities for 28 years.
For automatic class E fire suppression in server rooms and electrical panels without operator intervention, see the automatic suppression tube system.
For the complete guide to all fire classes, see the classes of fire guide.