Fyre

There are many different theorys about how dragons breathe fire. One is that they have a spark pouch in their jaw and their breath ignights the flint in the spark pouch, and so creates the flame.

Another theory is that they have different gasses or chemicals in their stomache and mouth and when they mix when the dragon breathes that creates a flame.

Yet another theory is that they have two stomaches. One they fill with meat and other food, and the other, they fill with bones or flamable substances so that when they make FYRE, their gasses in their stomaches catch the substances on fire and create a flame, which the breath blows out through the nose and mouth.

Yet another is that they have methane in their stomachs and when it mixes with another chemical it creats a flame, (its very like the second theory)

And yet another is that in their lungs there is a special type of bacteria that turns food into helium, this mixed with platinum licked off of deposits causes the helium to ignite and create a flame.

Like I said, there are many different theorys about how a dragon creates its flames. I dun know which ones are true or if any are, or if one theory only applies to one breed of dragon, and another, another. These are just theorys.