There is only odor when the toilet is flushed. When we are driving down the road the odor fills the entire vehicle when someone flushes. At times we have needed to open all the windows to get rid of the stink. We've had passengers almost vomit from the smell before.
Yes, I've checked to be sure the vent is not plugged. I put on a vent cover that is kinda like a weather vane and that has helped somewhat. This past trip we were parked out in the desert in 105 to 110 degree heat that didn't help things. We dumped the tank both right before and right after we left the desert.
I think I'll try the GEO method to see if it helps.
