Here is some useful information on Lipos which I think will help with understanding battery safety.
Informational page on all aspects of Lipo batteries.
http://www.rchelicopterfun.com/rc-lipo-batteries.html
The production process of Lithium-ion Polymer batteries.
http://youtu.be/6vBH6zlrXuM
Some burn testing of Lipos
http://youtu.be/VswaFOrVM6I