I heard a noise, looked over and was greeted with this

Isn't that a high end charger? What battery?
What kind of battery is that?
Looks like what remains of a Samsung25R.What kind of battery is that?
Looks like a samsung 25rWhat kind of battery is that?
This goes to show that electronic devices can fail, including protection circuitry in smart chargers. Also, any battery can vent, whether safe chemistry or not. Statistically, most battery incidents occur while or just after charging.
I always recommend that people charge their batteries on a flame-resistant surface: stove top, marble countertop, metal baking pan, pyrex dish, et al. I also always recommend to don't charge batteries when not physically present to monitor them.
I'm undecided about battery charging bags. These were designed for use with LiPo batteries/chargers for the remote control crowd. The batteries are not placed in a box charger like Lithium batteries are; the batteries are connected via wire connectors and placed in the charging bag, and the charger (the heat producing item) remains outside the bag. The negative thought is that placing a Lithium battery charger in a bag which is unventilated can cause heat and inadvertantly cause the charger or battery to catch fire or explode -- defeating the purpose of using the bag.