Odorlos is an excellent product
And often works in systems that aren't well-enough ventilated for K.O. to work. WM's description of HOW it works is way over-simplified and not QUITE accurate (they tend to edit what the mfrs give 'em to fit the space without really understanding it)--the nitrates actually help to release oxygen in the tank contents to create an aerobic condition so the waste can convert to CO2 (which is odorless) instead of coverting to noxious gasses...but the important thing is that, instead using toxic chemicals to kill bacteria (which also prevents solids and paper from breaking down), it works with the naturally occurring bacteria in waste to eliminate odor and break down solids and paper. If K.O. doesn't work for you, try it. If Odorlos doesn't work, NOTHING will until the ventilation in the tank is increased.