I edited a typo.

I don't own a gas oven, but I'm not surprised.

but I would take a look at the burner and flame color to make sure things look correct.

THE OVEN IS DEFECTIVE

The byproduct of properly burning natural gas is heat, water vapor and carbon dioxide. Carbon dioxide, what people exhale when we breath.

Carbon monoxide byproduct is usually when the oven is getting too much natural gas and there is not enough oxygen in the combustion to properly ignite all the natural gas. It a defect from the factory.

It is not normal for Thermador or any natural gas oven. Sometimes the orifice that feeds the oven natural gas is over drilled, the holes are too big, and the oven gets too much gas and there are trace amounts of carbon monoxide. But making your carbon monoxide detector go off reaches the point of the oven being defective.

This is interesting and might be a complicated issue.

First thing is that your CO detector is supposed to go off (I think) when it detects CO concentrations of around 70 parts-per-million (70 ppm). But they are not precision instruments and it might be reading a lot lower or giving false alarms (good news) or reading levels higher than 70 ppm (bad news.) Have you tried the dectector in different location or tried a different CO detector? Detectors can give false postive readings and UL had to come up with a standard for avoiding those. How old is that CO detector?

Second, both Weed and Deeageaux suggested you check the burner and flame. Do you know if either of the repair techs did that? If gas flow is not properly adjusted --- or if the flow system is badly designed or defective --- then not all gas gets burned and that flow can elevate CO levels. IIRC, about three or four years ago this kind of problem turned up in some Electrolux and Kenmore ranges, and CPSC order a pretty big recall.

Third, you say the oven has been doing this since your got the stove four years ago. Just to clarify for other readers, the fact that it has been going on for four years should rule out fumes from manufacturing oils and solvents that are supposed to go away during the initial oven burn-in. Also, the CO detector is going off when pre-heating the oven, right? IIRC. the Thermador gas stoves did not have self-cleaning ovens so I have to ask that you are pretty sure that old cooking spatter/stuff is not burning off the interior walls or floor?

Fourth, where abd where did the tech take the CO measurement that gave a 50 ppm reading? Was the reading taken during warm-up or after the oven had been operating for a few minutes? (You likely will get some CO as the burner starts up but it should go away within four or five minutes.) If he was measuring in the oven vent, he would be getting a concentration different from the room air. Apparently, the standards allow up to 100 ppm at the oven vent at least according to this source:.

http://www.homeenergy.org/show/article/nav/kitchen/id/1152

I suspect that Thermador is thinking that the gas concentration in the room, in general, will be below the max indoor air qaulity (IAQ ) standards so they don't pay much heed to the levels measured at the oven vent. Don't know this for a fact, but that's my guess as to why they said the tech's reading was "normal."

Fifth, the fact that the CO detector is going off suggests that Thermador's assumptions may not be correct. As I said, I think detectors are (theoretically, anyway) supposed to trigger at around 70 ppm. My memory is that the U.S. EPA standards for indoor air quality (IAQ) are that CO levels must average below 9 ppm over any 8 hour period and not exceed more than 35 ppm in any one of those hours.

That leads me to ask where your CO detector located in relation to your stove? Have you tried other detectors in other locations to see if the alarm goes off there, too? If so, you may be getting places in the room where CO is collecting if you do not run the hood, and that is a bit scary.

FWIW, I just tried an experiment with a known (and recently verified to be) good CO detector. Put it outside and hit the reset button and let it sit for half an hour to clear its sensor and give a good clean baseline. Then propped it up on top of the oven vent on my NXR gas stove. Ran the oven for half an hour. Then switched on the convection fan (which increases the flow of air and heat from the oven vent). Not a peep from the alarm.

I'll see if I can scrounge a CO meter and take some measurements.

This post was edited by JWVideo on Sat, Jul 20, 13 at 17:31

Thank you for the information. I'm interested to see what numbers you come back with on your range, JWVideo.

Yes, the techs took a look at the burner and flame. They also checked under the "floor" of the oven, as the tech once had an experience where the floor was bent and not allowing the gas to vent correctly. My oven floor is good. My oven is extremely clean, so the tech ruled out splatter.

It's only one CO detector that goes off, and it's the one closest to the kitchen. The detector is located approx 10 feet from the oven. It's through an open doorway at the base of my staircase.

It happened one time in the middle of Thanksgiving. I was hosting 30 people, so you can imagine my horror. We opened all the windows and doors. The oven had been on for a few hours. My tech informed me that to maintain the temperature, the oven cycles on and off. I'm wondering if too much CO built up with all the re-igniting.

I've gotten used to running the oven with my hood on. But it's just so noisy to have to do that...and scary to know that too much CO may be coming in.

PS. I just called Thermador and they said that since I am outside my manufacturers warranty, they couldn't help me. Thankfully, I bought an extended warranty from my appliance store. I'll speak with them again. Frustrating, but they don't seem to think there is a problem since Thermador told the tech that his reading was within normal range.

Umm, I don't see any mention of checking that detector. Detectors are relatively cheap warning devices and not precision instruments. They wear out, break down, come defective from the factory, etc. I've seen CO detectors signalling alarms where a CO meter says there is zero CO. Happened to me last winter. Alarm going off and CO meter right next to it read zero CO.

If you are running natural gas, your gas utility company may check it for you for free. Our rural area's fire department will do that for us, too.

This post was edited by JWVideo on Sat, Jul 20, 13 at 18:46

Are you on natural gas or propane? And is the oven configured correctly for the gas that you are using? If your flames are orange and you are getting CO1, then I'd suspect that to be the source of the issues. That goes back to installation, since you say it's done this since you first had it.

My sister's put out dangerous levels of carbon monoxide. After fire department confirmed it and company didn't take care of it..she returned it and bought a different brand.