Normal Fire
Normal fire is a natural phenomenon resulting from the rapid oxidation of material, producing heat, light and flame. It consumes fuel such as wood, oil or cloth, spreading according to available material, airflow and environmental conditions. Normal fire is affected by wind, dampness and lack of oxygen; it can be extinguished through smothering, dousing or isolation from fuel. It does not discriminate in its damage, affecting all creatures, objects and terrain equally within its reach.
In combat or dungeon settings, normal fire poses a persistent hazard, igniting flammable materials and potentially spreading if not contained. It typically burns at a temperature between 600°C and 1,100°C, depending on the fuel and oxygen availability. In the context of a combat round, 12 seconds, a fire at this intensity is enough to ignite paper, dry cloth, straw, parchment and other tinder almost instantly. Light wood shavings, dry wood splinters and pitch or oil-soaked materials may catch in that same window if directly exposed.
To sustain a plain, open wood fire — such as a campfire or contained blaze — the rate of fuel consumption depends on flame size, wood type, airflow and arrangement, but general medieval-style fires burn through fuel at a fairly predictable pace. A steady, moderate fire used for cooking or heat consumes roughly 2-3 lbs. of dry hardwood per hour. This amount keeps a fire hot enough to boil water or cook meals but without producing large flames or excess smoke. This would be a small fire occupying less than a full combat hex, sufficient for a party at rest or a guarded encampment.
Signal Fires
For a larger fire — something meant to be clearly visible, offer strong heat or begin spreading — consumption increases to about 5 to 9 lbs. of wood per hour. This is closer to a blazing signal fire or the early stages of a structure beginning to burn. To maintain full flame across an entire 5-foot hex, the rate rises further. Softwoods burn faster and with more flame but produce less heat per mass and require more frequent feeding. Wet or green wood smokes heavily and may fail to burn efficiently at all. Charred wood left behind from earlier combustion burns more slowly and with less heat, meaning a fire must be restoked with fresh fuel to maintain maximum effect.
A fully engaged fire covering one 5-foot hex, burning brightly with sustained flame and heat sufficient to ignite adjacent materials, would typically consume 22 to 33 lbs. of dry hardwood per hour, possibly more. If fuel is not replenished at this rate, the fire begins to lose intensity, first dropping to embers, then coals, then cooling entirely over the course of 10 to 15 minutes.
Alighting Wooden Structures
Standard hardwood of approximately an inch thickness, begins to char and smoke within 2-3 rounds, with ignition occurring after 5-8 rounds. With pieces two-inches thick, charring requires 3 rounds, with full ignition occuring between 8-10 rounds. Four-inch pieces char within 5 rounds and ignite after 15-25 rounds. Finally, 8-inch pieces char after 15-20 rounds, with ignition not occurring until 40-60 rounds. Moisture, coatings, airflow and shape (logs vs. planks) can alter ignition dramatically. Dungeon environments with dank, stagnant air that lacks oxygen, can delay ignition further.
Flat vertical surfaces like walls and doors tend to resist ignition longer than horizontal or enclosed spaces where heat can pool and build. External walls exposed to open flame will begin to char more quickly due to the supply of oxygen. Roofs made of thatch, shingles or tar-treated wood are far more vulnerable. Thatch can ignite in under 2-3 rounds and burn through entirely within a 15 rounds. Shingled roofs may resist open flame for a minute or more, but once caught, the fire can spread laterally and down into the rafters quickly, especially with wind.
Interior spaces behave differently. Fire beginning inside a structure — whether from a torch, oil flask or deliberate sabotage — gains heat rapidly in the confined air, accelerating ignition. Rafters, furnishings, curtains, floorboards and support posts all serve as fuel. Within 10-15 rounds, a room can become fully engulfed. Doors and windows become outlets for heat and flame, sometimes drawing the fire through the space violently.
Load-bearing elements, especially if exposed, are usually the first to compromise. Joists and floor supports may collapse within 25-40 rounds, bringing down upper levels or walls. Buildings constructed with wattle and daub, or plank over frame, can fail within a similar time, especially if fire enters wall cavities or attics. Once a structure is substantially involved, firefighting without magical aid becomes nearly impossible. Water must be abundant, targeted and continuous to reverse progress. In gameplay, structural fires often render the environment unusable within 30-50 rounds, unless actively suppressed or magically contained. The fire then becomes not just a hazard, but a transformative force — cutting off escape, removing treasure and altering terrain.
Fire Spreading through Vegetation
Assuming a typical combat hex that is already substantially on fire, the rate of spread into adjacent hexes depends heavily on fuel type, density, moisture levels, terrain slope and wind. Assuming average wind and ambient conditions, and ignoring magical influence, the following estimates describe natural, mundane fire behaviour across standard terrain types in 12-second D&D rounds.
In a normal, temperate woodland or taiga, where vegetation is generally moist and undergrowth is moderate, fire spreads more slowly. It may take 3 to 5 minutes — 15-25 rounds — for a fully involved hex to ignite a neighbouring one, assuming no strong wind. In tightly packed undergrowth or with accumulated deadfall, this could drop to 1 to 2 minutes. The fire tends to creep across the ground and smoulder before flare-ups. Snow or wet moss can delay ignition significantly, potentially halting spread altogether without sustained heat.
In macchia, maquis or dry steppe conditions, fire moves quickly due to oily shrubs, grasses and thin-leafed trees. Spread can occur in under 1 minute, often 3-5 rounds, and faster still if the wind is strong. Low, resinous plants like rockrose and juniper ignite rapidly and sustain flame well. Fire in this terrain may leap gaps, igniting patches not directly adjacent to the burning hex, especially if sparks or embers are carried on the wind.
In a jungle, the surface is humid and dense with vegetation, and while the volume of fuel is vast, moisture slows ignition. Surface fires may take 5 to 10 minutes — 25-50 rounds — to spread from one hex to the next under average conditions. However, if the fire reaches the canopy or climbs via lianas and dry bark, spread accelerates dramatically, jumping hexes vertically and horizontally within 1 to 2 minutes. Still, the overwhelming humidity often means that unless the fire is already advanced or artificially boosted, its progress is choked by steam and smoke before it can race outward.
These rates assume the fire spreads without active interference, and that no firefighting or magical suppression occurs. Strong wind, slope or fuel continuity will hasten spread in any biome.
