If your waste drain/plumbing system is working correctly NO odors will come in side your rig regardless off how dirty your tanks are.....
Black tank odors will only come from toilet (and some bathroom sinks if plumbed to black tank)
Bowl seal holding water.....vapor barrier
Floor flange...mechanical barrier
Grey tank odors can be from 'p' traps not holding water....vapor barrier
Air Admittance Valves......spring loaded/flapper....mechanical barrier
Grey tank odors can be as nasty smelling as black tank
Check under the kitchen/bath sink for a stub pipe. On top of stub pipe is an Air Admittance Valve. They just screw on/off. If they fail to close you will have direct access to grey tank for odors to get inside rig.
IMHO chemicals just mask odors....water is all I use.
No odors inside rig because MY odor barriers are working.
I don't even smell anything when dumping because my sewer hose/fittings are threaded and/or have seals...which provide mechanical barriers when dumping.
IF you can smell waste tanks inside your rig.......other than an occasional whiff when flushing toilet......your 'barriers' are faulty. Find/fix....no odors
Toilet seals
'P' traps
Air admittance valves
AND any loose/broken drain/vent fittings/pipes
