According to the Monster Manual the Balor should explode when they die.
Though by the book, this explosion would probably break the chests always, so maybe it can be made smaller.Death Throes (Ex)
When killed, a balor explodes in a blinding flash of light that deals 100 points of damage to anything within 100 feet (Reflex DC 30 half). This explosion automatically destroys any weapons the balor is holding. The save DC is Constitution-based.