Some scientists believe that dragons make fire through a process of digestive acids, the oxygen in the air and the minerals they get from rocks they ingest with their food.

Dragons will sometimes swallow their food whole, taking in both muscle and bone in large pieces. Their stomachs are similar to those of birds in that they have a separate compartment called the gizzard. Dragons will swallow rocks and grit which reside in this rough part of their stomach, acting like a grinding machine and breaking large bones into smaller pieces. During this process, bits of minerals in the rock flake off, creating the mechanism by which hydrogen and methane burst into flame when the dragon releases gas through its mouth and nostrils.

Other scientists believe that dragons are similar to some poisonous snakes in that they have a sac in their head which contains an acid. Dragons can obtain sulfuric acid by eating the plants in the permafrost that thaw out each summer. When they drink salty ocean water, they take in sodium chlorate. This sodium chlorate, in combination with glucose (sugar) from its food, will ignite when it is combined with sulfuric acid.