Deep cycle battery charging ventilation
Without the 50 reputation I can't comment yet.

Yes as the commemnt by Brian Drummond suggested, the ventilation is not your biggest problem. This battery looks capsulated, that means there is 1% chance of gas leakage and the ventilation is only for cooling.

There are boxes designed for this purpose that will keep the battery safe, but if the tank explodes, the battery will be next.

The human factor, of spilling, tripping, touching and other things also is a problem.

The same battery is located in all cars in the same way, there is no danger, except the standard 1%.

The ones who want absolute security just put a gas sensor nearby, you might already have the same type of gas sensor in your room.

Make sure no one spills anything on it.