Hallo Alisha,

perhaps not your small battery, but car battery can be really dangerous. And people working all day long with cars have a much higher probability to be injured. Car batteries MUST be stored in a separate room, with guaranteed ventilation.
What makes things worse is, that lead acid battery can produce H2 gas even if it's not charged, at all. Older lead acid batteries have some mud at the bottom inside of enclosure, which is the origin of permanently produce of H2 gas! You often can see the bubbles and hear them when shaking the battery.
I have seen a broken car battery which was only hit by some hot particles from an abrade machine (you also call this 'flex' in english?), some meters away. Battery really exploded, looked like a broken egg and all the acid could be seen arround. Happily no worker was in close contact to this battery.

By the way, Alisha, how do you proceed?

Bye,
Kai