IIUC more than CO production, the greater consideration with alcohol stoves is the fuel being used. What is the methanol fraction and what other denaturing compounds are in the mix? Reportedly, certain alcohol formulations are vile-smelling and quite headache-inducing.

To piggyback on the Zen stove notes, a major factor re. CO production is the distance between pot and flame. Many stoves have responded well (lowered CO levels) to raising the pot above the standard support height. Fiddling with one's own stove to figure this out would require a lab setup and instrumentation, of course.

Cheers,