Odors, and getting rid of them.
Bene odors? Haven't a clue, but if it's the head, here's the deal. Don't flush with saltwater. Use only a freshwater rinse, a cupful from the head faucet after a pee and pump the bowl dry. To take a dump, fill the bowl halfway with fresh water from the sink/shower faucet. Do your business, and pump the bowl dry. Rinse with freshwater again, pump dry again. Use a granulated deodorizer, not the liquid kind. As for diesel, don't fill the tank so full that fuel comes up the fuel hose and rests in it, it will seep an odor into the boat. That's how we do it on our boat.