how easily do Lithium Polymer (LiPo) batteries catch fire? 3. shorted

A safety video showing just how easily these common Lithium Polymer batteries catch fire and explode. I do this so you don't have to.
These batteries are in phones, drones, cameras, laptops etc etc they are the standard small grey packs ...these had puffed so although showing 4.2V carried far less actual current. (and due to puffing gaps between plates unable to deliver a high "C"). I used the small vice to bridge the contacts and hold the cell in place.
(these are 1 cell from a 3S 2000mAh drone battery pack)
All that any I tried did was to get a bit puffier and a little warmer - i expect a fully charged healthy cell would puff and burst into flames if the short was sustained long enough. I gave up on these after 15minutes as they weren't even hot to the touch.

The magic rule with LiPo: low charge = low risk.