I fretted for many months about installing home built Lifep04 batteries in my basement, on a rack next to a cement wall. Did my investigation of the risk and reached a conclusion.
My conclusion is that as long as you connect them correctly and the device they are connected to is fused, or has a circuit breaker (Sol-Ark 15k inverter in my case).
The risk of fire is no different vs any other electrical appliance in my home, and not as much risk as the large wood stove in my basement that I use in winter months.
Of course a squirrel could decide to pick up a wrench, sneak into basement, climb onto the battery bus bars, and then create a cell to cell short circuit...and possible fire.
But I can live with the likelihood of that event, and not lose any sleep at all about the 32 280ah LifeP04 cells sitting on shelves in my basement, next to my Sol-ark, and my cut off switch, and my main 200A panel, no "critical needs panel" runs the entire house, (4 ton Heat-pump, Well pump, and everything else) and I don't even notice if the grid disconnects.
The setup just works, and makes me happy to have installed same.
Of course I grew up in the day's when children played outside without supervision, rode bicycles without helmets, and adults smoked cigarettes in small meeting rooms for meetings that lasted 90 minutes with little or no ventilation.
Thank god we have cigarette's under control today.