If a person wishes to argue for rock people or fire people, they can do so, but not on a scientific base. Life is generally defined as having the characteristics of moving, breathing, reproducing, and responding to outside stimuli. Things like viruses and anaerobic bacteria are hard to fit into any definition, but Fire people would be even more of a problem. The reason that there is no other way is because of the chemical restraints on all of life's processes. In order for an animal to breath, for example, it is necessary that a gas be used that supports combustion.
Some gases burn like methane, hydrogen, propane, and the like.
Some gases smother like carbon dioxide, carbon monoxide, helium, and the like. Only a very few gases support combustion. When a piece of coal burns, the carbon combines with oxygen, producing heat and light. The process is unique because energy is given off in large amounts quickly, and we call it burning. When we breathe, the same thing happens, but not as rapidly.