In the now-locked thread about altered stoves dbailp wrote: That's always the case with pellet stoves, if your stove could put out CO it wouldn't be produced by itself because the stink of burning wood would accompany it. The kind of stove that can produce lethal amounts of CO is a gas heater, unvented to the outside. That's why they're illegal in California (and other states as well I'd guess). I'm not familiar with oil furnaces but assume they're even worse. Smokey wrote: The above link with take you to "English Handbook for Wood Pellet Combustion" -the definitive work on the subject, translated from Danish. It's a scientifically complete analysis of the subject. What stands out in the section that I read about combustion follows: "Gasification (pyrolysis) With further heating, the wood pellets start to emit gases. At approximately 270 Â°C gasification will produce the heat necessary to continue the process. Carbon monoxide (CO), hydrogen (H2) and methane (CH4) are created along with other hydrocarbons Gas combustion If there is sufficient oxygen present the gases will be ignited when they reach their ignition temperature. The hydrogen will react with oxygen and create water and the carbon of the hydrocarbons and the carbon monoxide will burn into carbon dioxide and water vapor. If the temperature is not high enough or there is not enough oxygen to feed the combustion, the gasses will be seen as smoke that will burst into flames, when the temperature or the inflow of oxygen is increased." It states that Carbon Monoxide is converted into CO2, so I guess that would mean that a stove that isn't vented to the outside may poison you from it's fumes but one of them isn't CO. It would be like sitting near a campfire and breathing its awful smoke, something that few can tolerate (unless they smoke 3-4 packs a day). I'd say that's some good news.