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On a scorching day in late May 2024, Delhi’s fire service took 220 emergency calls, its busiest that year. Officials had said at the time that around 70% of the incidents they responded to were fires triggered by electrical short circuits. Across that summer, emergency response calls for fires more than doubled from a year earlier to cross 9,000, and deaths more than tripled compared to the 10 recorded during the same months the previous year.
Parts of Delhi that summer saw temperatures close in on 50°C, and scientists later confirmed 2024 to be the warmest year on record in global history.
That was a brutal year, but heatwaves have become increasingly common for much of north India. Every summer, the region sees the same grim cycle of fatal blazes blamed on “short circuits”, electrical faults and air conditioners.
On June 3 this year, a fire at a bed-and-breakfast facility in Malviya Nagar’s Hauz Rani claimed 23 lives, including those of foreigners visiting Delhi for medical treatments. Less than a month later, on June 22, a blaze that engulfed a multi-storey building in Lucknow’s Aliganj killed 15, most of them youngsters.
In both the incidents, fire officials suspect short-circuits as one of the causes for the fires, which then spread rapidly in tinder-box structures that violated building and safety norms, and lacked proper ventilation and emergency exits.
While the definitive reason for the fires will only be declared once the inquiries are completed, the incidents raise a question worth looking into: what actually turns a wire or an AC into the spark that starts a blaze, and why the summer has so much to do with it.
Also read: The Indian dream that ended in Hauz Rani fire: How 3 generations were wiped out
An electrical current flows when positive and negative charges are connected; until then, the circuit is incomplete, and there can’t be any passage. And when electricity passes through a wire — any wire — it generates heat.
Wires are built to handle that heat up to a point, determined by their thickness, their insulation, and how much current they carry, and this is why they are supposed to be imperceptible to human touch. Stay within those limits and the heat is harmless. Exceed them, and the insulation begins to degrade — slowly at first, then faster, until it can ignite.
A short circuit is what happens when current finds a sudden, unintended path of very low resistance, bypassing the appliance it was meant to power and surging down that easy route instead. As it surges, heat builds rapidly, throwing sparks that can ignite anything nearby.
This is the version most modern homes are protected against: the circuit breaker in the fuse box is built to sense the surge and cut the power before the heat starts a fire.
But fires often begin more quietly, and the breaker fails to notice.
This unfolds over a long time. It begins with the same friction-heat inherent in any wire, but at a specific weak point on the path: a loose connection, or a thin wire feeding a heavy appliance. As resistance builds at that spot, more heat is generated there, little by little. The trickle is usually too small to trip the breaker, so nothing switches off; the fault simply cooks. Eventually, the heat at that spot can climb until it sets the material around it alight.
From there it becomes a trap that tightens on itself.
The danger spot is usually a joint — where two wires meet, or where a wire is screwed into a switch, plug or socket. As that joint heats, it slowly works loose, the way a bolt slackens under repeated strain, and a hair-thin gap can open between the two pieces of metal. Electricity doesn’t stop at that gap; it leaps across, and each leap can be a spark. The heat damages the joint, the damage widens the gap, the wider gap sparks harder, and the cycle feeds itself.
Also read: Lucknow tragedy: Height loophole left building exempt from fire checks
Every wire can carry only so much electricity before it overheats, and that limit isn’t fixed. A wire stays safe by shedding its heat into the surrounding air. The safe limits are typically calculated assuming the surrounding air is about 30°C. When it is hotter, the wire should ideally carry less electricity. In a Delhi summer, when temperatures increase, the heat has nowhere to go and the wire runs dangerously warm just doing its everyday job.
In a 2023 review published by EDP Sciences, authors Santhosh Kumar and Balachander argue that much of Indian electrical equipment is specified for an everyday ambient temperature of around 33°C, while summers now routinely see temperatures crossing 45°C outdoors. This quietly eats into the safety margin the wiring was installed with, i.e. a cable run through a hotter environment loses carrying capacity and overheats, degrading its insulation towards a short circuit.
In plain terms: wiring is pushed to its edge in the summer months, exactly when every home switches on its heaviest appliances for hours on end.
In May, a retired IAS officer died after a fire broke out at his Hauz Khas home in south Delhi. Fire officials said the fire was suspected to have been caused by an air-conditioner blast. AC fires have been reported across apartment complexes in Delhi-NCR, including Noida and Ghaziabad, over the past few years.
The AC packs several electronic failure dangers into one machine.
To get its compressor motor turning, an AC needs a big jolt of power at start-up — a burst running several times its normal power — delivered by a part that stores energy and releases it in that shove (a capacitor). That part is sensitive to heat, and on an outdoor unit, the sun alone can overheat it, on top of hours of running without rest. As the capacitor weakens, the motor strains, overheats and can burn out.
In some cases, the part itself overheats enough to start a fire. As it fails, it can throw sparks or cause shorts in the motor and wiring.
The review cited above added a mechanical route that’s easy to overlook: the constant vibration of an air conditioner can shake its connections loose, creating bad contacts that lead to short circuits. The early warnings are mundane and routinely ignored — odd noises, the unit cycling on and off, a burning smell, or smoke.
ACs in India are also shifting from non-flammable cooling gases towards newer ones that can burn — R-32, for instance, is mildly flammable and ignites only at certain concentrations. Some units also use a gas that is essentially propane, which is flammable.
The gas almost never starts the fire by itself; the electrical fault does. But a refrigerant leak around the outdoor unit, where the compressor and electronics sit together, can create an explosive atmosphere that a spark then finds. Even so, tests of the common gas produce a flash, not an explosion.
In National Crime Records Bureau’s Accidental Deaths and Suicides in India (ADSI) data for 2022, there were 7,566 fire accidents — the lowest in 25 years, but the share blamed on electrical faults and short circuits had risen to 21%, up from just 3% in 1996.
Fire officials in Delhi say about 70% of the incidents they respond to are caused by electrical faults — overloading, short circuits and overheating — in wiring too old to cope with appliances running around the clock.
The EDP review puts this figure at roughly 80% and says that the National Building Code 2016 gives too little weight to fire risk from electrical installations and appliances, and that defects in air conditioners play an outsized role in short-circuit fires.
Prerna Madan leads the explainers and immersives team at Hindustan Times, bringing more than eight years of editorial experience across India's three largest English-language newsrooms — Hindustan Times, The Times of India and The Indian Express. Her career spans the full range of modern news journalism: digital-first production, print news desks covering metro, national, and front-page, and editorial decision-making at the planning and commissioning stage. From managing coverage of Assembly elections and the Union Budget to steering the reporting, editing and production of in-depth reporting into the Delhi-NCR’s pressing issues, Prerna has honed journalistic storytelling that spans genres, topics and formats. Running through her current work is a facility for complexity — translating consequential, difficult material in the fields of policy, science, environment and politics into rigorous, accessible journalism that sets out to answer two critical questions: why it matters, and what happens now. Prerna holds a degree in English Literature from the University of Delhi and a postgraduate diploma from the Indian Institute of Mass Communication.
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