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NOTE: I am aware of the recent Grenfell fire. While it inspired this question, I mean no disrespect to the victims of this tragedy.

Centuries ago, before modern fire brigades, there were a number of cities where a small fire turned into an entire city being burned down. Events like the Great London Fire of 1666 destroyed hundreds of houses after a bakery caught fire, and there have been records of fires destroying thousands of houses before being stopped in cities like Shanghai.

However, with modern fire brigades being able to respond much faster and with much greater effectiveness, would a fire like the London Fire of 1666 or the Shanghai Fire of 1894 be able to occur today? I know that there was a fire in Gatlinburg last year that damaged or destroyed 2400 houses, but I consider that a rural situation. I'm talking about a major city the size of London, New York or Los Angeles being burned to the ground because someone accidentally dropped a candle. I preferably want a scenario where there aren't any extreme outside aggravating factors, like an earthquake or other disaster happening at the same time.

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    $\begingroup$ Modern cities are much less combustible. They are no longer made up of many closely spaced houses built of wood. This being said, it can happen if the fire is big enough; see the tragic fates of Dresden and Hamburg in the last world war. $\endgroup$ – AlexP Jun 21 '17 at 11:40
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    $\begingroup$ In order for this to happen, major mistakes need to be made. Maybe people cut the number of fire workers drastically. Maybe inspections are not being made. Maybe people use cheaper material that aren't save (I'm aware). Maybe someone needs to profit, for example someone that wants to build new houses, and actively prevent firefighters (could've still happened accidentally initially). Most likely all of this together and much more. Could you maybe specify if this is allowed? $\endgroup$ – Raditz_35 Jun 21 '17 at 11:45
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    $\begingroup$ It's not just modern fire brigades that stop this. In fact, it is mostly modern Fire Codes that prevent it. See this document for example: nfpa.org/~/media/files/codes-and-standards/… $\endgroup$ – RBarryYoung Jun 21 '17 at 15:26
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    $\begingroup$ Yeah, it's the fire codes -- both their existence and how well they're enforced. The recent Grenfell Tower fire in London apparently was as bad as it was because the building did not conform to existing fire codes. Certainly fairly sizeable "modern" cities in 3rd World locations could see something much worse. $\endgroup$ – Hot Licks Jun 21 '17 at 18:32
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    $\begingroup$ @Richard Two words: bat bomb - en.wikipedia.org/wiki/Bat_bomb proven to work, never actually deployed because they went with the nuke instead. $\endgroup$ – Baldrickk Jun 22 '17 at 7:12

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A modern city is mostly concrete and glass. These materials do not burn near as well as wooden structures used to, back in the day. Modern cities also have high-pressure water systems to make sure fire fighting teams have plenty of water for their hoses. And they have hoses, not buckets.

But modern cities have buried gas lines. And factories that produce highly combustible or explosive materials. And population density is far higher -- ancient cities didn't have high-rise apartment buildings. And we have aerial bombardment to deal with as well.

WikiPedia lists major fires here. The most deadly fire it lists in the 21st century so far is an armoury explosion fire in 2002 that killed 1,100 people. There's a fire in Manila that left 8,000 people homeless. A brush fire in San Diego destroyed 2,232 homes.

But that compares quite favorably (at a statistical level) to fires in the 1930s, like the one in 1934 in Japan, where a house fire spread. That left 2,166 dead and 145,000 homeless. Or a 1923 Tokyo fire after an earthquake that razed half a city and over 100,000 dead.

Or the 19th century, where we have a Nova Scotia fire in 1897 that destroyed 80% of Windsor, Canada.

Looking over that list, it appears that modern building methods, modern fire fighting methods, and other safety measures (smoke alarms, etc.) have greatly improved our ability to respond to fires. Modern fires tend to not spread to entire neighborhoods. Exceptions exist, such as in case of brush or forest fires or other major natural disasters.

But the toll on human life is certainly going down.

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    $\begingroup$ Also worth mentioning the 2003 fires in Canberra that caused relatively little loss of life but a lot of property damage. They could have been much worse. en.wikipedia.org/wiki/2003_Canberra_bushfires $\endgroup$ – Mike Scott Jun 21 '17 at 13:21
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    $\begingroup$ Brush fires in San Diego are pretty much the norm. There's at least one every summer in southern California, and while not all of them get to the "evacuate" or "actually burned homes" level, it's still a common occurrence. It's California's version of Florida being hit by a hurricane (although CA is more known for earthquakes outside the state, they don't happen that often, statistically speaking). $\endgroup$ – Draco18s Jun 21 '17 at 17:10
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    $\begingroup$ "And population density is far higher" Not true. Many ancient cities had much higher population densities, as it was necessary to walk everywhere, so many amenities had to be within walking distance of one's home. $\endgroup$ – Euphoric Jun 22 '17 at 5:44
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    $\begingroup$ And factories that produce highly combustible or explosive materials. Most zoning regulations place those way outside populated areas. $\endgroup$ – SJuan76 Jun 22 '17 at 9:48
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    $\begingroup$ The Cedar Fire, the San Diego brush fire that destroyed 2,232 homes, was driven by hot dry winds that at times reached 60 mph. A 6 lane freeway with a concrete median was not an effective fire break. Arguably that was an "extreme outside aggravating factor" similar to an earthquake. $\endgroup$ – Patricia Shanahan Jun 22 '17 at 12:01
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It could happen, but it would take some precise combination of factors to make it so. You would need something to take down the fire brigades, paralyse the transport infrastructure, and stop a federal response.

It would help to have slums around, since they are usually built without respect to regulations, have roads with difficult access, and will have a lacking infrastructure.

**EDIT:**A friend reminded me of Centralia, where an underground deposit of coal caught fire and ended turning the city into a ghost town.

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    $\begingroup$ I agree with the idea of slums. A big city surrounded with massive slums (Rio's favelas, maybe, or more probably some african cities) could have a hard time if a fire started there and wasn't dealt quicly enough. Once fire gets big enough it's self-propelled and hard to stop even with a lot of resources - see the tragedies in Portugal and London this past week. $\endgroup$ – Rekesoft Jun 21 '17 at 14:58
  • $\begingroup$ Not just the transport infrastructure -- you'd need to have it so the building infrastructure is highly vulnerable (total slum conditions could work, depending on the building materials that things are cobbled together from). $\endgroup$ – Shalvenay Jun 22 '17 at 22:16
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Fire code says no

Modern cities with well-enforced building standards have a massive edge over their counterparts 100 years ago in the form of largely noncombustible/fire-resistive construction for key buildings and party walls, zoning rules that help prevent combustible buildings from being abutted too closely to each other, and even the widespread application of active automatic fire suppression inside buildings. Downtowns and other high-density areas in particular are aggressively fire-resistant in design and implementation, relying heavily on the factors mentioned above to keep fires manageable.

These combine to make fire spread within buildings and from building to building vastly more difficult. Wildland-interface suburbs, due to their lower-rise, more combustible construction and the higher surrounding fire load, are more vulnerable to such a conflagration than downtowns. Even then, though, building code development has been catching up to prior experience in these matters, requiring improved exposure fire resistance in such applications.

Even buried pipelines and factories aren't enough to touch off a wide-scale disaster in many cases -- transmission pipelines can be shut down remotely if they start to leak, and zoning keeps hazardous industries largely separated from residential areas.

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The possibility of a major city experiencing a major fire due to accident on the part of people (or Mrs O'Leary's cow) is slight to very slight.

Cities are just not combustible these days. They are made of concrete, not wood. Even with the somewhat wood based major cities of the early 20'th century, the city destroying fires during that time were all the result of deliberate and massive bombardment by purpose built incindiary bombs: Hamburg, Dresden, Tokyo (and quite a few other larger Japanese cities).

The worst example: 16 square miles of Tokyo were burned out in the fire raid of March 9-10, 1945, deaths estimated to exceed 100,000. But, that required over 300 B29's, each carrying five tons of napalm, and that was with a good deal of the buildings of Tokyo being made of wood and paper.

There is one scenario whereby a major city might be flattened or set alight by an accident today. If a tanker ship containing liquified natural gas were to catch fire, the resulting explosion would be close to a small nuke, and the resulting fire could be extensive.

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  • $\begingroup$ How do you come up with that last part? Especially with "the resulting eplosion would be close to a small nuke" ? This seems extremely unlikely, since the gas requires an oxidizing agent mixed with the cas, in order t explode. otherwise it would 'only' burn from the outside of the 'bubble' of excaping gas. $\endgroup$ – Burki Jun 22 '17 at 9:26
  • $\begingroup$ just guessing here, but sounds like he is refering to a fuel-air effect: en.wikipedia.org/wiki/Thermobaric_weapon . $\endgroup$ – Tuncay Göncüoğlu Jun 22 '17 at 12:22
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    $\begingroup$ Yes, it would be a fuel-air effect. The larger LNG carriers are potentially very dangerous, as LNG will vaporize into an explosive mixture if released into ambient temperatures. Far more dangerous than a simple oil tanker. $\endgroup$ – tj1000 Jun 22 '17 at 12:38
  • $\begingroup$ @tj1000 -- if you look at the aftermath of the Buncefield disaster -- the nearest building exposures, despite being badly damaged by the blast, did not suffer significant fire damage AFAIK. $\endgroup$ – Shalvenay Jun 22 '17 at 22:10
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No, because modern cities have wide streets

A bit of background: I currently live in Trondheim, which had a story of being destroyed by fire... on multiple occasions. Let me quote from its Wikipedia article, emphasis mine:

The city has experienced several major fires. Since much of the city was made of wooden buildings, many of the fires caused severe damage. Great fires ravaged the city in 1598, 1651, 1681, 1708, twice in 1717, 1742, 1788, 1841 and 1842; however, these were only the worst cases and there have been several smaller fires in the city. The 1651 fire destroyed 90% of all buildings within the city limits. The fire in 1681 (the "Horneman Fire") led to an almost total reconstruction of the city, overseen by General Johan Caspar von Cicignon, originally from Luxembourg. Broad avenues like Munkegaten were created, with no regard for property rights, in order to stop the next fire.

Wide avenues act as architectural firebreaks. If you have ever seen how firemen fight wildfires, you sure have noticed that the strategy to putting wildfires out is to actually not put them out, but create enough firebreaks with bulldozers while you airdrop enough retardant to give the bulldozers time, and just let it burn.

In a modern big city you already have firebreaks: big avenues, motorways, and even open spaces like parks (which can be bulldozed out if needed) will prevent the spread of the fire.

In a city-wide fire scenario, I expect the fire brigades to act the same way as in wide-scale wildfires: make sure that the firebreaks are clear, and make sure that they work (station firemen at the not-burning side to quench any small fires that might happen due to falling embers). They will not be trying to put the fire out, they will be trying to make sure the fire doesn't spread to the next block.

Even if you assume a nightmare scenario where all the buildings are covered in Greenfell-tower-like flammable cladding, firemen would still be able to contain the fire as long as they can contain it using wide avenues (obviously while not trying to put it out, thus costing more human lives).

It is plausible to think that an entire slum district could burn down, but not the entire city.

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Conceptually, because of fire codes and other advancements in urban planning, architecture, policy, it shouldn't happen. However, the other side of the problem is to look at the human factors involved.
A lot of people have already posted answers in consideration of this, but I am specifically thinking of ways that social stigma allows fires and natural disasters to proliferate (among other factors at hand). The cases I've read aren't about entire cities per say, but significant portions of them (if Manhattan burned down in New York, that's kind of it's own mini-city).

99% Invisible covered the burning down of Chinatown and how

Residents of Chinatown were largely unaided by their neighbors during and after the disaster. The fire department, for instance, focused available resources on the wealthy residents of nearby Nob Hill, dynamiting buildings in Chinatown in an (unsuccessful) attempt to stop the flames from spreading.

Also, notably in California, large fires are a byproduct of other events (earthquakes/natural fires encroaching urban areas). Chain reactions can make fires a lot worse than they would be on their own.

Another example is from the San Francisco 1906 fire. I've read more about it elsewhere, but this talk by a San Francisco professor Robert Cherny touches on the compounded effects of natural disasters and discriminatory decisions public servants practice. Not saying this always happens, or that all public servants are like this, but it's not uncommon either.

Brigadier General Frederick Funston was the acting commander of the federal troops at the Presidio. Acting on his own initiative and without any legal authority, Funston marched the troops into the city “to aid the municipal authorities. . . .” Mayor Eugene Schmitz welcomed the decision and ordered the troops and the police to shoot looters. In effect the city was under martial law.

It did not go well. In an attempt to prevent looting, the authorities ordered residents off the streets, a blunder because the order discouraged people willing and able to fight the fires from doing so, although many pitched in anyway. The troops and police targeted poor people and ethnic minorities with their “shoot to kill” orders. Some of the soldiers and police officers themselves looted.

In the absence of a functioning water supply, the authorities tried to create fire breaks with dynamiting, but the explosions may well have made the fires worse because the crews did not know how properly to use dynamite.

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  • $\begingroup$ Welcome to WorldBuilding.SE Remy! Nice answer. If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$ – Secespitus Jun 22 '17 at 17:11
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Well, technically, yes. But emergency responders would probably need to be absent. Also, the city in question would have to have enough flamible material to keep it going. Perhaps there was a celebration recently, spreading around a lot of paper confetii or other similar things around. If the city has a lot of planted trees that would also add fuel. If the fire hit a fireworks factory, that would help spread sparks around.

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I guess with modern cities everyone thinks of the modern parts of the city first, but some cities (including London) have old town centers or other older parts (or slums, they can work in a similar way for this scenario). If your fire starts in that part, you have more "options".

Houses are still made of inflammable material and might not be particularly well kept

This is not the "pretty old center" tourists look at, this is just some residential area where the buildings have been around for a long time and people just kept them up without doing major renovations or just doing cheap renovations. (Yes, that is borrowed from the Grenfel fire. It can happen everywhere.)

Streets are narrow and houses close to each other

Old streets were not built for large fire trucks. While the fire brigade struggles to get through, the fire is jumping fast from one dry attic to the next. In a city that normally does not cope with forest fires, the availability of means to extinguish a fire from the air might be small and would have to be brought from far away, which gives the fire even more time to spread.

Make it social

If it was not an accident but an angry mob setting fire to a given "enemy", this same mob would try to keep anyone away who tries to extinguish it. At some point, they would have to leave the dangerous area, but at that time the fire can already be out of control. The mob has also added fuel to the fire in the meantime or hid explosives or other dangerous material which makes it too dangerous to get close or use standard methods to extinguish the fire.

Let it start in multiple locations at once Even the largest fire brigade can be spread out thin until help arrives.

Let it smolder Maybe it is something wrong with the gas supply which leads to smoldering, undetected fires in multiple locations. Or electric transformer stations have been serviced by a company who made multiple mistakes that also lead to smoldering which at some point breaks into a fire. This scenario also somewhat "helps" with the fire breaking out at multiple locations at once. A smoldering fire can already be spread far before it is breaking out or detected. And situations in which there is smoldering are often harder to extinguish as well.

Of course, not all of this works when "someone accidentally dropped a candle". But from the beginning, this is a hard start, as that someone obviously sees the candle fall and can act immediately.

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  • $\begingroup$ You'd need a very old district for that -- i.e. something predating all notions of fire code. Fire-resistive party walls will stop what you're talking about pretty much dead cold in their tracks. $\endgroup$ – Shalvenay Jun 22 '17 at 22:11
  • $\begingroup$ Might I mention that in Europe a lot of cities do have districts that would fit the description? Just because it does not exist in an American metropolis it is not something unheard of. $\endgroup$ – skymningen Jun 27 '17 at 6:24
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This is actually more plausible than it seems. I remember reading an article (will try to find it later and add a link) dealing with modelling of a large fire in a certain modern city (can't recall which one exactly, but I think it was Moscow). The surprising result was, above a certain size/intensity, the fire was self-sustaining, with concrete burning and immense winds fanning those flames and spreading them over hundreds of meters. It had something to do with regular layout of buildings directing winds in a special way.

Of course, that study was assuming the "candle" dropped was a medium-sized nuke, which isn't exactly what you were looking for. However, I find it quite plausible that, if you pick the point (or points) right (and modern computational resources can help you find the winning setup), you could start a similar self-sustaining fire on a smaller scale at first. Such a fire could grow to envelop few building blocks within an hour, which is fast enough to avoid being extinguished too soon. After that, regular firemen would be unable to do anything, while extraordinary measures will take some time to get approval — time that the fire will use to engulf the whole city (and millions of civilians trying to flee in panic won't help either).

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Bruce Sterling had a short story in Wired back in 2000 called "Newer York, New York" that started off with a brief scenario for a modern great fire.

Essentially hot summers from climate change enhanced by the heat island effect cause the neglected electrical grid to overheat and eventually catch fire which took out the gas mains.

New York was versatile and tough, sure, but it had never been designed for week after week of blistering tropical heat.

People were used to the occasional burning car at rush hour. That's why emergency helicopters routinely hauled two-story-high sacks of water out of Jamaica Bay to the Long Island Expressway. But then the insulation on the old electrical mains started burning beneath the streets. Finally the DC current lines blew - and took the gas mains with them.

Sudden explosions ripped up Broadway, Fifth Avenue, 42nd Street - great flaming trenches that had once been the principal thoroughfares of Manhattan. New York autoincinerated. Fire leached into tenements, tourist traps, infotainment stores, and expressionistic corporate towers.

Source: https://www.wired.com/2000/01/futuretekture/

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  • $\begingroup$ Welcome to WorldBuilding.SE! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$ – Secespitus Jun 23 '17 at 13:03
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Wildfires near big cities are a probable trigger for such an event. Recent example, which fortunately has been rapidly under control, is Sand Fire in 2016 near Los Angeles, CA.

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No I would say the probability is near 0. When is the last time a fire destroyed an entire city? A loooong time ago.

That fact alone shows you that modern cities cannot be ENTIRELY destroyed by a single source of fire.

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It would be exceedingly unlikely but it could happen. Combine hot, dry, windy weather with a fire in something like a refinery. Under normal conditions the fire brigades will stomp on any fire but if the fire gets too big too fast they will be overwhelmed. At that point a fire could get out of control.

Yes, modern cities are far less combustible than the cities of old but that won't stop a big enough fire.

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Overground? Probably no, unless there was a severe gale passing through (essentially disabling the fire service and letting the fire jump gaps) but that might count as a second disaster.

An underground fire is another matter. A city built over a coal seam isn't impossible and those can catch fire in ways that can't be extinguished.

If your entire city suddenly loses structural integrity, it would be destroyed. This is a natural version of a medieval siege tactic.

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Another scenario comes to mind, it would require some laxness with safety for it to come about:

You need a city with a LNG (Liquid Natural Gas) terminal either in the city or placed such that the tankers must pass by it to get to the terminal.

A tanker is going past and the helmsman suffers some sort of medical incident that causes a major commotion. In the chaos nobody (modern ships can have very small crews) notices the tanker has turned towards the city until it's too late. One of the tanks suffers a major breech when it runs into something. The broken tank makes a decent boom on it's own, when the gas detonates (it will disperse and at some point find an ignition source) you've got a boom up there with a backpack nuke.

Start enough fires and the firefighters won't be able to stop them, especially if the boom takes out a major water main. (A big part of what lead to the loss of WTC 7--when the twin towers came down they seriously damaged the water system there and the firefighters didn't have much to fight the WTC 7 fire with.)

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  • $\begingroup$ Would that really start enough secondary fires to be an issue though? (See Buncefield for an example of a similar incident IRL) $\endgroup$ – Shalvenay Apr 6 '18 at 11:49
  • $\begingroup$ @Shalvenay Note that that blast occurred at an oil terminal--a place designed from the ground up to deal with catastrophic fire. Little outside it was burning. I'm talking about the detonation occurring someplace not set up with that degree of fire engineering. $\endgroup$ – Loren Pechtel Apr 7 '18 at 0:53
  • $\begingroup$ I mean -- the buildings surrounding Buncefield were quite badly damaged, but they did not catch alight all the same -- I suspect that it was because that the flamefront (detonation front even) didn't have enough dwell time to heat things up to ignition...and I don't think that'd be the case in your hypothetical wide-scale NG blast, either $\endgroup$ – Shalvenay Apr 7 '18 at 2:01
  • $\begingroup$ @Shalvenay Explosions do not directly light stuff on fire for the very reason you state. Do enough damage, though, and fire would be expected. $\endgroup$ – Loren Pechtel Apr 7 '18 at 2:04
  • $\begingroup$ From what fuel and ignition source combination though? I can come up with a list of fuels on one hand, and a list of ignition sources on the other, but it seems like you wouldn't get a reliable meeting-in-the-middle (I can think of many cases where you had a gas explosion in a building and that was more or less it, with no secondary fire there either) $\endgroup$ – Shalvenay Apr 7 '18 at 3:04
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Is the city allowed to be a modern third-world city? If so, much of the city outside the CBD could plausibly still be very flammable, with lax enforcement of fire codes (bribing the code inspectors can do wonders for getting them to look the other way) and little access to public services (like, say, the fire department).

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