Situation: a mage casts Demiplane to create a wood-walled plane, then torches it before pushing a target into it with the ending of the spell's duration. This essentially seals the poor target into an eternal fire dimension.
The 8th level spell Demiplane creates a small plane, 30×30×30 feet, made of wood or stone. When the spell's duration ends, the entrance disappears and anything within is trapped in this alternate dimension.
Obviously, in reality, such a situation couldn't last forever (the fire would run out of air and extinguish quickly). Is this possible in D&D, however, given the limits of the spell and the game's limited rules coverage of how fires work? Moreover, what would happen to the Demiplane once its walls were consumed (assuming they even could be, as I don't recall rules for wood being consumed!)?