Black tank deodorizers

I don't see the need for chemicals of any kind in the black tank for odor control or to aid breakdown except for when a deep cleaning is needed. The toilet is only open to the tank for a very brief moment and you shouldn't normally be smelling much of anything and if you do, it could be for another reason. I make sure it's well flushed after each dump of the tank. A vent fan can draw more odors into the bathroom.

I spent every summer in my youth at my parent's cabin and it had a very stinky outhouse, especially in the summertime. An RV toilet is like perfume in comparison. (Then there was all the mosquitoes, spiders and wasp nests.)