There is an underground city in a multi-level cave with two entrances; it is otherwise enclosed. It's shaped more or less like an inverted pyramid, getting narrower with increasing depth. A fire breaks out at the top level, which contains a wide, open area and is also where the first entrance is. The second entrance is at the bottom. The volume is around 50 million cubic meters, half of it air and half of it cave walls. The fire has quickly grown to a degree that the locals cannot contain it, and they must evacuate.
Most real-life fire safety manuals are written with the assumption that only the ground floor can be used to escape, which is not the case here.
My main questions are: Which entrance (if not both) does the smoke go toward? Which entrance (if not both) does the carbon dioxide go toward? If carbon monoxide is generated, which entrance (if not both) does it go toward? What other byproducts can be expected here?
Details that may affect the answer:
- Atmospheric pressure is 5x sea level atmosphere, but composition is the same as regular air.
- The lower part of the cave contains chemosynthetic fungi that recycle carbon dioxide into oxygen with a combined capacity of around 100 tonnes per day. However, these fungi are themselves very flammable, and if the fire spreads downward (which it can) it will quickly consume them.
- The primary material being burned is not exactly wood but a dried fungus-derived material of similar flammability; although the "wood" is an omnipresent building material in the inhabited areas, the high ceiling of the top layer is bare rock.
- The upper and lower entrance are about equidistant from the source of the flames.
- Each entrance has an area of around 10 square meters, which is not enough to evacuate the population in time.