Buy some self activating fireballs. I have one on top of each of my metal wire racks, and also tempered glass between each shelf and miner to prevent one from killing them all. If the heat and fire actually spreads the fireball takes care of the shelf and the room.
What is a self activating fireballs?
They are just normal balls, which you throw in a fire and they splash open or something, thus extinguishing the fire.
Its a better alternative to the fire extinguisher. And you could just leave it aside the miner, and it will extinguish it itself.