Wait. But surely this is a joke, right? You are certainly aware of this phenomenon. I’ve been whooshed, yes?
And inasmuch as ignition usually destroys the (chemical) parties to the combustion, I’d say that a few more matches in the office environment would definitely enhance that environment (as if anything could).
A quick internet search turns up phosphine (PH3) and diphosphine (P2H2) as the substances charged with making the Will o’the wisp burn. This is consistent with my memory – I originally got this info out of Mellor’s Comprehensive Treatise.
This site says William Corliss claims that no satisfactory mechanism has been demonstrated for this effect:
http://en.wikipedia.org/wiki/Will_o’_the_wisp
I’m not sure what to make of that. The phosphorus compounds definitely ignite spontaneously in water and damp air – there are plenty of references for that (and Jules Verne used the effect in his often-overlooked book “Tribulations of a Chinaman”). Maybe he means that no one has demonstrated that rotting matter could produce phosphines that will spontaneously burn. Corliss stated in a much earlier book that some meteorological phenomena were unexplained that had, in fact, been well-understood for a long time (and I corresponded with him about this). I know other scientists have been looking over his shoulder, and suspect he’s gotten better, so I’ll give him the benefit of a doubt on this one.
Well, you wouldn’t really have any flames untill the chemicals reached the air outside the body. Or they could be mixed to exit the body in seperate but converging streams. The streams would converge some distance from the body.
I think the most likely scenario is that any animal that engages in this type of defense would invariably end up burning down the forest, ergo, their home and offspring would perish. But don’t let that foolish logic detract from continued insightful thought.
CC, certainly, YouTube is our friend 
Extremely unlikely? Yes. Impossible? I don’t think so. Our stomachs are shloshing with acids that would be no fun to have on bare skin. Skunks, venomous snakes, Portuguese men-of-war, wasps and stingrays (RIP Steve Irwin) all carry and deploy unpleasant substances. It’s not too great a leap of the imagination to think of critters that could exhale fire.
An enormous dragon taking to the skies under its own power, though, seems farcical.
There was a novel by Thomas Page called The Hephaestus Plague, about insects which caused fires by rubbing their hind legs together. Crickets already exhibit this behavior (minus the fire-starting), so it’s not that much of a stretch to imagine such a beast coming into being. OK, so it’s not exactly “fire breathing”, but neither is the above mentioned bombardier beetle.
Howzabout a firefly? Instead of a controlled chemical reaction that causes light maybe that could be sped up to induce a spark?
Or they’re desert, arctic or deserted mountaintop dwellers without flammable substances nearby.
Animal Planet network had a show called Dragon’s World: A Fantasy Made Real in which they tried to come up with a mechanism for fire-breathing.
Their idea was bacteria in the gut producing hydrogen gas. The hydrogen would be stored in a bladder until needed. The hydrogen bladder also helped them fly, by providing buoyancy.
Their dragons would chew on platinum-bearing rocks. Bits of platinum stuck in their teeth would provide a catalyst for igniting the hydrogen.
This is assuming one would use the oral cavity. I’d propose that the nostrils would work better. Firstly, contact with the atmosphere could better be controlled, secondly, separate nostrils would allow for seperation of reactive chemicals. Also, I’d think one could “aim” the fire stream more accurately using the nostrils. One thing we haven’t considered, ignited methane being expelled under pressure creates a blowtorch effect, useful for offencesive tactics. However, wouldn’t a substance such as phosporus create more of an explosion rather than controlled combustion. Forestfire fighters use a liquid based kerosine torch to leave behind a trail of fire, wouldn’t that be more useful than a blast of flame? I can quickly pass my hand under a blowtorch without harm, but being doused with flaming kerosine produces a less desirable effect.
You typed it that way on purpose, didn’t you?
No, not at all. The static charge developed by a nylon t-shirt is more than sufficient to produce a spark which will ignite methane. Such a charge is totally useless as a means of defence.
As for fire ‘breathing’ itself, I think a two step process along the following lines is plausible:
STEP 1: The development of a workable flame weapon.
*) A creature spits to defend itself. There are already plenty of creatures that already do this, from snakes to camels.
*) The spit becomes increasingly noxious by the addition of volatiles: ketones, alcohols, terpenes. Once again, the addition of noxious volatiles to defensive body secretions is widespread, from skunks to bombadier beetles.
*) At some stage the addition of volatiles produces a flammable mixture. Not a huge leap.
*) The addition of acids from the stomach produces an exothermic reaction capable of igniting the mix. Such reactions aren’t instantaneous, but if you pour a strong concentated acid onto a wad of grass or paper it will combust within seconds. Since the stomach is already handy to the mouth and already produces a nicely noxious acid this step would seem almost to obvious NOT to evolve.
*) Our animal now has the equivalent of naplam in it’s armoury: a wad of sticky, flammable material that bursts into flame a few seconds after it leaves the animal’s mouth.
All the steps so far are easy to produce by simple evolutionary development. Far simpler than what we see with the bomabadier beetle. And we now have a camel that spits napalm. From that point we have a workable basis for developing classical fire breathing.
STEP 2: The devlopment of true fire breathing
*We have a basis for the evolution of the ignition system (the napalm system is more effective if there is no delay while waiting for a chemical ignition). Something as simple as a row of hairs could provide a static spark that could ignite volatiles.
*We have a workable basis for development of a flammables production system. The salivary glands in ruminants like camels have already been modified to store and secerete nitrogenous wastes, and the glands in various reptiles store and secrete numerous non-salviary enzymes as venom. It’s a plausible step to develop glands to store and secrete alcohol.
At this point we can actually discard the precursor system of producing napalm. Our animal can spray alcohol directly at a target and then ignite the stream mid burst. The alcohol will immediately vapourise and hey presto:
WE HAVE ACHIEVED FIRE BREATHING.
Well actually we have achieved a primitive flame thrower, but the practical distinction betwen this and fire breathing is non-existent.
How about getting the flammable material from it’s diet - something like Lycopodium (Lycopodium - Wikipedia), used frequently in fireworks and explosives could do the trick. The animal eats this plant, but can’t digest it, and it somehow gets stored and dried inside the body. On command, it can spit this right back up (I’m imagining something like rabbit pellets, but still in powder form, not compressed). As for ignition… I don’t know. Some sort of fire striker in the mouth, I guess.
http://www.chembio.uoguelph.ca/chemclub/images/04_college_royal/04cr04.jpg
That’s a picture of our “real” fire breathing dragon at a chemistry show at the university I went to. Originally designed for “Pyrek” (loosely based on “Shrek”), he/she/it has pretty much had a role in the show ever since, AFAIK. A loose pile of lycopodium was placed inside it’s mouth, and a lit candle in front of it (the inside of the head is a large paint can). A long rubber tube led down the neck and into the mouth of the person acting as the dragon. Simply blowing through the tube blew the powder through the candle flame, and a large burst of ignited powder would emerge, lasting a second or so. If that didn’t blow out the candle, you could often get another shot or two at it.
Truly a popular show character. Scared the crap out of some kids nearly every year!
Lycopodium burns really rapidly, so we could also use it to throw “fireballs”. Similar idea - pile some powder into your hand near the base of your fingers, place a lit match between some fingers (which are curled up to hide the match), raise your hands slowly (for dramatic effect) and then swing them down quickly - POOF! Very impressive.
I need to see if I can get my hands on some of this stuff now… 
You’ve all missed it.
Look at all the posts discussing probability and likelihood. If we just alter probability, we can change the statistical likelihood of dragons until they actually exist. Mathematician Stanislau Lem said so in The Dragons Of Probability. He also hints that by “juggling the matrix” we can make the dragons grand.
In Anne McCaffrey’s “Dragons of Pern” series(Dragonflight, Dragonquest, The White Dragon and about a dozen others, but notably Dragonsdawn, the most scientific/technologically advanced book in the series) the dragons breath was powered by “chewing phosphine-bearing rock” called “firestone” which the riders would carry in bags and the dragons would chew before breathing fire. The dragons chew it an hour before their first flame and continually chew it during periods they need to sustain flame. The firestone is diverted into a second stomach where the gas is released and belched forth on demand. The dragon trains with their rider to lean to control the gas flow and build the duration of their flame breath. Also there is a massive regurgitation of all the leftover stone material from the specialized stomach later on.
Enjoy,
Steven
Are you asking whether it’s likely to happen given our current environment?
Or are you asking, given any environment possible, is it possible?
It seems to me an interesting related question would be, in what niche of our current environment would this be an advantage? It would probably have to be a comparable or more efficient method of achieving some goal that is already being satisfied in that niche.
With a long-burning product, a creature in a suitable environment could use the thermals to make flight easier. Hence, our dragon—althought, this wasn’t really about dragons. A mountainous rainforest, perhaps, where the plants are wet enough to prevent wildfires (or a medieval city on Discworld ), a flock might produce enough updraft to achieve height in flight. Just a thought. I just finished Guards! Guards!