what i dont get is how hot does the cell have to be to explode? my crazy mate had a small fire going, he then thru his old rc plane battery pack in the fire

and left it there! i said he was a crazy f***, but he just walked away and the fire was still burning away. we came back 10min later and the fire had just gone out and the cells hadnt exploded or popped! not one, only damage was the cell's heatshrink covering melted away and thats all. he tried the pack out and they worked, abit
so how in the hell did they not blow up after being put in a damn fire!?