The history
A million years from a fire in a cave to glowing halogen tubes, oil radiators, self-limiting ceramics and heat pumps, and the angithi that still kills in closed rooms.
For almost all of history, a warm room meant a fire in it, with its smoke. Romans and Koreans learned to hide the fire under the floor, and Franklin and Rumford squeezed more heat out of stoves and fireplaces. Then electricity arrived: glowing wires, nichrome that could glow for years, fireclay rods, halogen tubes, oil radiators and ceramic stones that refuse to overheat. Today heat pumps move heat instead of making it, while across North India the old angithi remains both a comfort and a deadly winter danger.
c. 80 BCE
Central heating by hot gas under the floor (hypocaust)
Sergius Orata (attributed), Roman Republic
1742
Iron stove standing in the room to warm the air
Benjamin Franklin, Philadelphia
1800
Infrared discovered
William Herschel, England
1855–1857
Working heat pump
Peter von Rittinger, Austria
1906
Nickel–chromium heating wire
Albert Marsh, USA
1912
Fireclay-element electric fire in production
Charles Belling, England
1955
PTC barium titanate ceramic patent
Philips, Netherlands
1959
Practical tungsten-halogen lamp
General Electric, USA
1000000 BCE – 1700
Hearths, braziers and fire pots warm people directly; Romans and Koreans send hot smoke under floors.
1000000 BCE
c. 1 million years ago
Far inside Wonderwerk Cave, scientists found ash from burnt plants and bits of burnt bone in layers about a million years old. It is among the oldest secure signs of people using fire, though some researchers argue for older ones.
Why it mattered. A fire in the living space was humanity's first room heater, and the first source of indoor smoke.
1000 BCE
c. 1000 BCE (possible)
The ondol carries smoke from a kitchen firebox through channels under a stone floor and out of a chimney on the far side. Traces at Unggi may date to about 1000 BCE, and some researchers point to even older Neolithic dwellings; the dates are debated.
Why it mattered. Heating the floor turns a whole room into a gentle, low-temperature radiator, the same idea as underfloor heating today.
80 BCE
c. 80 BCE (attributed)
Roman baths and villas were warmed by a hypocaust: a furnace pushed hot gases through a space under a floor raised on brick stacks and up through flues in the walls. Vitruvius credited the businessman Sergius Orata, though similar heating may be older.
Why it mattered. It is central heating: one fire, and the heat carried round a building by moving hot gas.
1600
by c. 1600 (Mughal era, attributed)
The kangri is a small earthen pot of hot embers in a wicker basket, carried under the long woollen pheran through Kashmir's winters. It was certainly in use in Mughal times; a story that it came from Italy is disputed. Its bigger cousin across North India is the angithi, an open brazier of charcoal or coal.
Why it mattered. Portable braziers still warm millions of homes in the Himalaya and the northern plains, with all their risks.
1700 – 1885
Iron stoves and better fireplaces, the discovery of infrared, the bimetal strip, the heat pump idea and the fourth-power law of glow.
1742
Franklin designed an iron fireplace that stood out in the room, with a hollow baffle that let hot fumes warm the air around it before they left. He described it in a 1744 pamphlet and refused to patent it. David Rittenhouse later fixed its poor draught.
Why it mattered. Getting more heat into the room and less up the chimney is what every stove since has tried to do.
1759
For his third sea clock, H3, Harrison bonded strips of brass and steel together. Brass expands more when warm, so the strip bent as the temperature changed, which he used to correct the clock.
Why it mattered. The same bimetal strip opens and closes the thermostat in oil radiators, irons and heaters today.
1796
1796–1798
Rumford made fireplaces shallower, with widely angled sides and a narrow, smooth throat. The slanted sides reflected more radiant heat into the room and the chimney drew smoke without pulling out so much warm air. His papers appeared in 1796 and 1798.
Why it mattered. Shaping surfaces to aim radiant heat at people is what a radiant heater's reflector still does.
1800
Herschel split sunlight with a prism and put thermometers in each colour. The temperature rose from violet to red, and rose again just past the red end, where there was no visible light at all. He had found infrared.
Why it mattered. Infrared is how radiant heaters, the Sun and an angithi's glowing coals warm your skin.
1852
Kelvin showed that a machine running a heat engine backwards could pump heat from cold outdoor air into a building, delivering more heat than the work put in.
Why it mattered. It is the idea behind the heat pump, and an AC in heat mode, which gives about three units of heat per unit of electricity.
1856
1855–1857
Rittinger built a heat pump that recycled heat to evaporate brine at a salt works, the first practical machine of its kind.
Why it mattered. Heat pumps took a century more to reach homes, and are now the most efficient way to heat a room.
1866
The missionary doctor Elmslie described cancers on the bellies and thighs of Kashmiris who carried kangris against their skin every winter. He first blamed the burns; later work pointed to tar from the smouldering charcoal as well.
Why it mattered. Heat sources held close to the body for years can harm skin, a warning that still applies.
1879
1877–1879
From John Tyndall's measurements of glowing platinum wire, Stefan worked out that a hot body radiates in proportion to the fourth power of its absolute temperature. Boltzmann derived the law from theory in 1884.
Why it mattered. It explains why a halogen filament at 2,200 °C pours out infrared while an oil radiator at 75 °C barely glows.
1885 – 1950
Resistance wire turns electricity into heat. Nichrome and fireclay rods make the glowing electric fire a household object.
1891
1891–1894
Crompton's company showed electric heating and cooking devices at the 1891 Crystal Palace exhibition, made an early electric kettle and by 1894 sold a catalogue of 'Domestic Electric Machinery, Electrical Heating and Cooking Apparatus'.
Why it mattered. Heating by resistance became a product you could buy for the home.
1895
1892 – c. 1895
Dowsing demonstrated electric cooking at Crystal Palace in 1892. Around 1895 he invented radiant-heat lamps for treating rheumatism, and a 'luminous radiator' of long glowing bulbs in front of a reflector to heat rooms.
Why it mattered. The glowing tube in front of a reflector is still the design of every radiant heater.
1906
Marsh patented nickel–chromium alloy, nichrome. Its resistance is about 66 times copper's and, when hot, it grows a thin skin of chromium oxide that stops it burning away.
Why it mattered. Nichrome made safe, long-lived electric heaters, toasters and kettles possible, and is still in most heater coils.
1912
Belling, who had trained at Crompton's, patented heating elements of resistance wire wound on fireclay (patent 19,054). His 'Standard' fire, with six glowing firebars in a cast-iron surround, was his company's first product.
Why it mattered. Wire wound on a ceramic former is exactly the 'rod heater' still sold across India.
1940
c. 1940s
Banks of infrared lamps were used to dry and cure paint on military equipment much faster than ovens, and car makers took them up in the 1950s.
Why it mattered. Industrial infrared taught engineers to build fast, focused radiant emitters like those in today's quartz heaters.
1950 – 2000
PTC ceramics, halogen tubes, portable oil radiators and better stoves with flues.
1955
Researchers at Philips found that barium titanate, doped to conduct, has a resistance that shoots up just above a certain temperature. Their patent, filed in 1955, founded PTC thermistor ceramics.
Why it mattered. PTC stones in today's ceramic heaters throttle their own power, so they cannot overheat if the air is blocked.
1959
GE patented a practical lamp with a tungsten filament in a small quartz tube filled with halogen gas, which returns evaporated tungsten to the filament so it can run hotter and last longer.
Why it mattered. The same tubes, with filaments near 2,200 °C, became the halogen heater: warmth within a second of switching on.
1974
1974 (some sources say 1975)
In the first oil crisis, the Italian parts maker De'Longhi launched its first own product: a portable, oil-filled electric radiator on wheels. It sold to millions of homes.
Why it mattered. Sealed-oil radiators give gentle, even heat with no glow and no fumes, which made them a favourite for bedrooms.
1988
The bukhari, an iron stove burning wood, coal or sawdust with a pipe to carry smoke outside, has warmed Kashmiri and Ladakhi homes for generations; its origins are unclear. In 1988 a Srinagar firm began making improved bukharis under a licence from Germany's Wamsler, according to Kashmir Life.
Why it mattered. A stove with a flue carries smoke and carbon monoxide outdoors, which an open angithi cannot.
2000 – today
Doctors and officials count carbon monoxide deaths from braziers, while heat pumps become the efficient way to heat.
2017
A study of every fatal carbon monoxide case autopsied at AIIMS New Delhi from 2010 to 2015 found 40 deaths, about 80% in winter, peaking in January. Almost all happened in closed rooms without ventilation, most often with a firepot.
Why it mattered. It showed that angithi deaths are a predictable, preventable winter pattern, not bad luck.
2022
India's accidental deaths report for 2022 listed just 10 deaths from carbon monoxide gas for the whole country (13 in 2021). News reports alone count more than that in Delhi in a single winter month, so most such deaths are probably recorded under other causes such as suffocation.
Why it mattered. Without good numbers, the scale of heater poisoning stays hidden; the true toll is unknown.
2023
2022–2023
In 2022 Americans bought more heat pumps than gas furnaces for the first time, and about 3 million heat pumps were sold in Europe in 2023. The IEA estimates heat pumps met about 10% of the world's building heating needs in 2021.
Why it mattered. Moving heat instead of making it cuts the electricity for the same warmth by about two thirds; an Indian split AC with heat mode can do the same.
2024
January 2024
Delhi Fire Service said 15 people died in Delhi in January 2024 after using angithis in closed rooms, and more than 20 across the wider NCR. They included a family of four and a young mother with her two-year-old son.
Why it mattered. The fix is simple and free: never burn charcoal or coal in a closed room, and never sleep beside one.
Did you know?
A 2,000 W heater and a 2,000 W kettle make exactly the same amount of heat each second. Every electric heater is 100% efficient; only a heat pump beats it.
A kangri's embers keep its outside at about 66 °C, and Kashmiris carry it under the pheran all winter.
'Bukhar' is Persian for heat or fever, which gave the Kashmiri bukhari stove its name.
India's official records listed 10 carbon monoxide deaths for the whole country in 2022; Delhi's fire service counted 15 angithi deaths in the city in January 2024 alone.
A halogen heater's filament, at about 2,200 °C, radiates brightest at about 1.2 µm, just beyond red light; an oil radiator at 75 °C radiates brightest at about 8 µm.
The people
active c. 95 BCE · Businessman and inventor · Roman Republic
Credited by Vitruvius with the hypocaust, heating by hot gas under a raised floor.
1706 – 1790 · Printer, scientist and statesman · British America
Designed the Pennsylvania fireplace in 1742 and refused to patent it.
1693 – 1776 · Clockmaker · England
Invented the bimetallic strip for his H3 sea clock; it now works heater thermostats.
1753 – 1814 · Physicist and inventor · British America, later Bavaria and England
Reshaped fireplaces to radiate more heat into rooms and send less up the chimney.
1738 – 1822 · Astronomer · Hanover, working in England
Discovered infrared with a prism and thermometers in 1800.
1835 – 1893 · Physicist · Austria-Hungary
Found that radiated power grows as the fourth power of absolute temperature.
1832 – 1872 · Medical missionary · Scotland, working in Kashmir
First studied the skin cancers of kangri users in 1866.
1845 – 1940 · Electrical engineer · England
His company sold some of the first electric heating and cooking appliances in the 1890s.
c. 1859 – 1931 · Electrical engineer · England
Built radiant heaters from long glowing lamps in front of reflectors.
active 1900s · Metallurgist · USA
Patented nichrome in 1906, the wire in most heater coils.
1884 – 1965 · Engineer and manufacturer · England
Patented wire-on-fireclay heating elements in 1912.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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