I used this RecPro RV Antifreeze -50Ā°F Protection Non-Toxic which is Ethonal-free, assuming it is the Ehtonal that triggers this. So far, knock on wood, no alarming for me. And I have had it alarm a few times with three of us sleeping. It still has propylene glycol in it. It seems ethylene glycol, which some types of antifreeze use, can produce carbon monoxide when it decomposes at high temperatures.