I'd concur. Hydrogen is the smallest, lightest, and most "slippery" of the elements, comprised of a single atom. It's difficult enough to keep it in a sealed container, any hydrogen released under the hood of a vehicle will immediately dissipate without the help of a fan. What you really want to avoid is the accumulation of hydrogen, or, more correctly, hydrogen sulfide gas, from the charging of the batteries. As long as your batteries aren't under some type of enclosure that could cause the gas to "pool up" in an inverted hollow, you can just as well forget it.