Drawback of Lithium-Ion, page-14

This CSIRO report certainly is a great read, thanks!
Couple of quotes:-

There is currently no consensus on the appropriate method to extinguish a lithium battery storage fire in the event of an incident. Present suggestions... include use of sand, liquid nitrogen, water mist, lithium chloride or foam, or to simply do nothing.
(I guess doing nothing would be  within my capabilities.)

Compared to other battery storage types, there is less concern about the risk of fire with flow batteries.

Also I notice that they tend to call it thermal runaway, sounds so much easier to deal with than fire, or explosion.