I'm in the process of creating a plausible fire-breathing dragon, halfway through. As I don't want my dragon to have to eat stones to spit fire or light sparks because that could limit the dragon to certain regions, but as it will be used as a mount, this is impractical, I have made it have glands that allow it to produce a flammable oil from the fat of the animals it eats. Initially I thought of the dragon heating the oil so much that it would self-ignite when it was expelled, but the temperature needed for an oil to self-ignite varies, but is usually around 200º C. I thought the dragon could raise the oil's temperature through blood circulation around the oil bags that could accelerate until the oil is hot enough to self-ignite. However, according to L.Dutch, the blood temperature does not increase above the animal's body temperature, so it would not be possible to do that. He suggested using a mixture similar to the bomber beetle but in a stronger version as the mixture only goes up to 100º C. But I don't know of any more potent substance that an animal can produce biologically. So, to light the oil I thought of sparks, researched and saw that electric sparks are flammable ​​and then I thought of electric eels. My dragon may have organs responsible for generating enough voltage to create sparks. However, would an animal be able to produce enough voltage to generate sparks, and if so, what would be the complications for the animal itself?

Dragon information: When with the neck raised (like a quetzalcoatlus), the species can reach a maximum of 4 m in height, with a weight ranging from 250kg to 300kg. The wingspan varies from 16m to 19.50. These numbers are because, although the species is no taller than a quetzalcoatlus, it is larger because the neck is thicker which is where the flammable oil will be produced and stored, the tail is larger to help sustain stationary flight while firing (although it hinders flying straight as birds and bats do because the tail would sink and the nose would rear up), it has horns as it makes it more menacing and also helps to attract mates and it also has teeth (unlike quetzalcoatlus). It's a warm-blooded creature. It is carnivorous.

  • $\begingroup$ Unlike the last question, this one I added more details, more clarity. I'll delete the other one, although I can't... $\endgroup$ Nov 27, 2021 at 6:46
  • $\begingroup$ Title of question made me think you wanted to set a dragon on fire. $\endgroup$
    – Lemming
    Nov 27, 2021 at 7:21
  • $\begingroup$ @WizardKing, you can't delete a question once it gets answers. It's bad form toward whoever put effort in writing answers, and once it's posted, it belongs to the community. $\endgroup$
    – L.Dutch
    Nov 27, 2021 at 7:32
  • $\begingroup$ Puts, so my this new post will be closed as a duplicate... $\endgroup$ Nov 27, 2021 at 7:48
  • $\begingroup$ Agree with L.Dutch, I put an answer to the previous one worldbuilding.stackexchange.com/questions/217828/… ...... there are several options the dragon could use.. maybe you could put above text on top of the other one ? this opening text is better. $\endgroup$
    – Goodies
    Nov 27, 2021 at 11:51

1 Answer 1


Depends on how big you want those sparks

The voltage required to produce an arc of 1 meter is 3.4MV(30 000 000V). Unless you have a mechanical dragon this is ludicrous to even suggest a creature has the ability to produce this.

The voltage required to produce an arc of 1 centimeter is about 30 000 volts. Only about 38 electric eels at the same time. I don't know if the voltage of electrogenic organs scale with size but this might be more or less possible with a large enough dragon if they do. Perhaps a nice reason for why juvenile dragons can't breathe fire but adults can due to the inability to produce enough of a voltage to create the arcs/sparks if you want that sort of thing.

The voltage required to produce an arc of 1 milimeter is about a 1000 volts. A specific species of electric eels can go up to 860 volts. Not enough to produce an arc that can even be seen, but if it can be pushed up to 860 then it shouldn't be too unlikely for it to be pushed to 1000, maybe 1200 to be sure of a 1mm arc, perhaps many arcs if the two points between which the electricity would jump were numerous. I think this is the most likely to succeed in lighting a fire through a sprayed mist of oil ballpark, and once there is some sort of fire present the dragon can regurgitate the oil in a higher volume than the mist and produce a larger fire, perhaps producing a flame-thrower-like effect.


Forgot about the 'complications' section of the question with regards to an animal generating the required voltages.

Electric eels have been observed to sometimes shock themselves, either accidentally or because they can't help it. They have a layer of fat serving as insulation so they tend to be protected from their own electricity but as is observed this protection isn't always iron-clad. It's even possible for them to die from this but my understanding is that the mortality rate by self-electrocution of EEs is small. Should an animal generate even higher voltages, enough for arcs, that animal will more than likely require even greater fatty insulation to protect itself. Then again eels are in water and that might have to do with why they shock themselves so frequently. Maybe a land/air-based animal would not need this layer, but since we don't have an air-dwelling animal to compare with it may be prudent to assume they'll need it. Should they not require it but don't have it and try to generate their voltages underwater then they'll most likely kill themselves, not an ideal situation.

Since the dragon is intended for riding, might I suggest an appropriately designed seat and harness as far as materials are concerned, or rider's suit?

  • $\begingroup$ Wait, can a 1mm arc already ignite the oil? Because if so, then the dragon just fires up and continues to expel oil for a long breath equal to the movies and series. $\endgroup$ Nov 27, 2021 at 10:39
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    $\begingroup$ @WizardKing Electric arcs are some pretty hot things but an arc alone would probably not ignite a large mass of oil, which is why I suggested it first sprays an oil mist that is ignited into a flash of fire by the arc before it spews the oil in earnest which would then be further ignited as it is sprayed. I'm taking a page from grain dust explosions here. Most of the time it is not the fuel mass itself that first catches fire or causes an explosion but instead its vapor, gas, mist, or dust. $\endgroup$
    – Lemming
    Nov 27, 2021 at 10:52
  • $\begingroup$ What if the dragon threw the vaporized/pulverized oil, or whatever the correct term is, using the electric arc and then, when the flame ignited, released the jet of oil? All this in a matter of seconds. $\endgroup$ Nov 27, 2021 at 11:48
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    $\begingroup$ @WizardKing A properly timed sequence of this process, probably refined over millions of years into instinct, tells me there isn't anything obvious as to why it wouldn't lead to the effect of seeming to breathe out fire when it's more like a cough/spark/foomph and throwup in reality. The fun thing about an oil/grease fire is that it sticks and burns even worse when water is thrown onto it, so 'dragon fire' would have its associated increased effectiveness over normal fires against pretty much anything. Hope the people putting out the fires have a lot of sand. $\endgroup$
    – Lemming
    Nov 27, 2021 at 11:59
  • $\begingroup$ Good to know that this sequel would work... I'll make one more post asking about it just to make sure it's plausible, but I'll leave it for another day, I've already asked a lot of dragon questions. $\endgroup$ Nov 27, 2021 at 12:04

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