Fire, like its real-life counterpart, is an immensely destructive force. In-game, entities on the map which are on fire flash red and yellow. In item lists, anything which is on fire will also be surrounded by double exclamation marks, like ‼THIS‼. Fire will burn grass, shrubs, logs, clothes, dwarves (and generally all creatures that are not composed of fire-safe materials), wooden furniture, wooden buildings and wooden roads, lignite and bituminous coal rocks, and bars of charcoal and coke. Except for dragonfire, fire won't burn rock, metal or trees. Constructions (wall, floor, etc) will never burn, no matter what.
A fire can stem from several sources, for example:
- Dragons breathe dragonfire, which can set things on fire and will melt most metals, at anything hostile they see. The dragonfire spreads out in a conical shape and burns anything it touches.
- A fire imp can throw fireballs, which may set things alight.
- Magma can and will burn anything flammable it touches. However, any item set alight by this method will likely just be doused in magma until it is completely destroyed.
- Magma mist burns stuff just as well as magma.
- Some titans, forgotten beasts, and demons can breathe fire/throw fireballs, too.
- Fire men and magma men, as well as other procedurally generated beasts composed of flame, have high fixed body temperatures, causing them to spread fires (and fun) in their path.
Note that it is currently difficult to safely start (and then control) a fire. Fire is most easily started by either magma or a fire breathing attack. An area enclosed by water, metal, stone or Z-level difference can be used to start a fire which can be used as a way of increasing FPS by removing objects or can be used as part of a complex trap, though this may lead to fun when something comes out burning which then sets the rest of the fort on fire. Players of modded DF can have fire-breathing (fire spell casting) goblin castes.
Fire will not spread across Z-Levels by itself. Walls with trapped passages block the fire too. Trees and shrubs will not catch fire, but you can set them on fire in Adventure Mode.
One thing to note is that dwarves that burn to death do not leave remains and will produce ghosts even if buried in a coffin. Be sure to engrave a memorial to all dwarves that burn to ashes, unless of course you want a ghost infestation.
Dragonfire is a very powerful form of fire that reaches temperatures much above regular fire, up to Buildings (but not constructions) receive the full effect of dragonfire, so it should easily burn or melt all buildings and items. Even nether-cap wood, with its fixed temperature, ignites in dragonfire. Metal objects, however, can withstand many rounds of dragonfire, which is probably a bug. Objects ignited by dragonfire burn at their standard combustion temperature - only the initial blast of dragonfire is hot enough to destroy fire-safe materials..
Dragonfire can only naturally be emitted by dragons.
Artifacts constructed from a flammable base material can burn. As Artifacts don't wear away fire does no damage. Artifacts will burn endlessly without being destroyed. So long as the artifact is not stored in a bin water will extinguish them. If a flammable artifact is used as part of a building it can still burn.
The main problem with fire is that dwarves tend to ignore fire, up to and past the point where they become ‼Dwarves‼. As such, typical dwarven activities will be carried out despite the fact the dwarf is both burning to death, and will spread the fiery destruction to his peers. This will not only kill your dwarves but also incinerate a good many useful items. Dwarves will not path through smoke reliably, so if you see a bunch of job cancellations due to pathing issues, a firey dwarf is probably running around (or other fun is afoot). And don't, for Armok's sake, let the flaming dwarves anywhere near the booze. Contrary to popular belief, it doesn't explode (and never did), but it will boil away into nothing, which is always fun.