As many cart owners know, lead acid batteries generate hydrogen gas as a by product of the charging process.
And hydrogen gas was used as the lift gas in the Hindenburg ... that airship that exploded in 1937.
Here is an interesting video on "What Happened to the Hindenburg?" that may help some BGW members to understand why proper venting is required when we charge our lead acid batteries.
https://www.youtube.com/watch?v=VJy17qZmhjE