Hmmm... It just occurred to me: The back of our battery switch is in the starboard lazerette, just above the (possibly) hydrogen-gas-producing batteries, said lazerette of which is separated from the engine compartment (gasoline-powered engine) by painted peg-board.
Catch-22 situation, here: Have to turn on the switch to activate the blower. I imagine these switches are designed to minimize sparking, but still...
I think I'm going to add: "Open the starboard lazerette before turning on switch and blower" to my first-start-of-the-day routine. That will both vent any over-abundance of hydrogen (lighter than air) and give me an opportunity to sniff the compartment, all in one go.