Has to be a spark somewhere to set off the out gassing. Might make sure the battery terminals are tight...
I guess I have been fortunate as the only time I was close to a battery explosion was back in the day when the gas stations would offer a quick one hour charge by sending a battery around 50VDC and having a capacity of a couple hundred amps of current available. This was the way batteries were charged way back then. This one blew the battery top up over the gas station and spewed battery acid everywhere..
When I was in the service you always had to have the batteries in a steel cage when being charged haha... Times changes everything...
Roy Ken