The only thing I can add to this conversation to those, beyond all logical reasoning, that still think they need chemicals, is to ask you to try just using water. Rinse your tank out real good (soap, water and a little highway movement will do the trick), keep the over head vent closed and fan off when flushing and just see if you still have a problem. If you do, try to locate exactly where the odor is coming into the rv, as there will be a seal or something amiss and you'll need to correct it.
And to Tinstar, if you think this post was over a long time ago, why are you still here?
Ron