"sonst explodiert es"

So check this out,
I have a coal oven in my bedroom (we burn wood briquettes- it smells better). These coal ovens work like this: you start the fire and, with good airflow, let the fuel burn down to a clean burning red hot ember. Then you close the doors and flue to block the airflow, and the red hot ember transfers all of its energy, over the course of about 6 hours, into the brick/ tile oven. The oven (basically just a big brick block with a chimney snaking through it) stays hot and heats the room for about 12 hours.

There is a rumor that these things can "explode" if you cut off the airflow too early, and I assumed it was because of the expansion, contraction of the brick and thought the "explosion" would be more like a big crack down the side, ruining the oven. Then I researched.

IF you block the airflow of a fire, as you may guess, it smokes a whole lot. That smoke is un-burned matter, ie still contains plenty of energy. If you close off the airflow too early, these ovens will fill with smoke. Hours and hours of black, putrid smoke coming off the wood or coal briquettes. Plus, its really hot. SO, you have a big brick box filled with a superheated, unburned fuel/air mixture. BOOM! When these things explode, it doesnt just ruin the oven, it usually takes out the whole building.
COOL!!!