I had someone perform a combustion safety test on my oven today and he discovered that it's producing an elevated level of carbon monoxide compared to average: 80 PPM. He said the best ovens he's seen produce about 10 PPM. He said that I could get somebody out here to "adjust" it to improve the combustion but wasn't too sure what this would entail.

What does this entail? Is there like a user-serviceable knob on the oven to adjust the air mixture or something that I can do myself? If not, or if it's not safe for me to do this myself, who do I need to hire and what do I need to ask them to do? Or is the oven itself simply totally defective and in need of replacement? It's not a fancy high-end unit but it's fairly new...

  • I don't know anything about adjusting ovens, but: are you sure this is worth pursuing? If 10 PPM is "the best," what is typical? What was the level in the rest of the kitchen (which is really the value that matters)? I agree with @SomeGuy, this seems like a casual test procedure. I would get a CO detector and keep an eye on it. If you get one with a digital readout it will tell you the PPM in the air. I'm surprised the CO specialist did not seem to have anything helpful to say about the result.
    – Hank
    Mar 29, 2015 at 4:35
  • Most CO detectors don't alarm until CO is high enough to make a healthy young adult sick - the UL standard requires they not go off until 80ppm - which is plenty to make senior citizens and young children VERY sick. Get a "low level" CO detector. Nov 24, 2016 at 6:00
  • I looked into that, but a low-level CO detector was expensive. Instead, I saved the money and replaced the gas range with an induction range, which produces no CO.
    – iLikeDirt
    Nov 24, 2016 at 16:18

4 Answers 4


Great questions can always be asked with only a few words.

But my answers never seem short.

The short answer is that the stove can not breathe. Give it more air. Problem Fixed.

What is happening, the chemistry answer:

Carbon Monoxide is made when too much natural gas is burning in too little oxygen.

Good -> Natural Gas + Lots of Oxygen + Spark = Carbon DIOXIDE + Water + 100% Heat

Bad -> Natural Gas + Not enough Oxygen + Spark = Carbon MONOXIDE + Water + 50% Heat

  • You now know how CO (carbon monoxide) is made, and that making it wastes energy.

    It also stops blood from working. That is a different lesson.

  • An oven burner while it is working. Gas Valve, Gas line orifice,and Venturi Tube. Flame Manifold.

Short rant about poor quality testing:

Breathing air with 10 ppm of CO is better than breathing air with 80 ppm.


I hate that you were told this by someone you were hoping could improve your safety, it is a case of a little knowledge is dangerous.

I think it is great that you had a test conducted.

People that put any effort into testing are almost always better off than those who do not. Just because they are people who at least think about such things.

It annoys me that the guy that did the testing was so unknowledgeable. I am sure he intended to be helpful. Sadly he left more questions than answers.

Much longer rant about bad test procedures:

If I tell you my car gets 0 miles per gallon, you might think that is bad.

If I add that I got this measurement after I was trying to climb Mt Everest in my car, It then makes sense. Well, 0 miles a gallon makes sense. Conducting a test like that, it makes no sense.

You have to know what you are testing, and you have to be testing the same thing.

I tell you 80 ppm of CO is high, and I have seen 10 ppm, who knows what that means?

Was the oven running for 5 minutes or 30, was it preheated to 400 degrees, or 100, was he 1 foot away or 3, was he using an in date calibrated meter, was the air in the room moving or still, was the room 68 degrees or 78 ?

I am not asking you these questions, but they are valid questions, and I am wondering if he took all this information into account when he gave you the number of 80 ppm.

If he takes me to his 10 ppm oven, I can get his meter to read 200, or 0, without 'adjusting' the oven.

  • I was standing there with him. The oven was set to 350 and he was reading it right at the vent under the control panel. His meter read 100 ppm initially and then after 10 minutes it stabilized to about 80 ppm.
    – iLikeDirt
    Mar 29, 2015 at 3:47
  • I agree, this procedure for testing sounds very non-specific. Another possible variant: the size of the vent on different ovens may allow more or less ambient air to mix with the exhaust, which would change the PPM reading.
    – Hank
    Mar 29, 2015 at 4:38

I work for a Natural gas co. for 20 years we suggest you have a hood vent and run it when ever you are cooking with your oven this will take care of the problem, The oven can be adjusted to help most of the time but, it's going to put out CO that's why we suggest hood vents we will red tag oven unsafe if levels get around 70 ppm please invest in a hood vent that vents to outside

  • And make sure your hood actually uses the outside vent. We had one once that leaked most of the air back into the kitchen because the installer didn't bother to seal the joints.
    – mrog
    Jul 6, 2018 at 21:41

There is no air mixture adjustment. If it's making CO then the airflow is simply blocked.

Check all the vents, perhaps insulation moved, or there is something there. Also possible for rodents to live in an oven, and they'll move insulation to make a nest.

There are vents on the bottom, and one on top behind the burners in the back (under the control panel).

What color is the fire in the oven? It should be blue. Too much red/orange is not good.

  • I think you just got a term mixed up. It is expected, to get carbon dioxide [CO2] from combustion. Carbon monoxide [CO] is the product of poor combustion. A small but important difference.
    – Some Guy
    Mar 29, 2015 at 3:40
  • @SomeGuy You are correct, I fixed my typo.
    – Ariel
    Mar 29, 2015 at 15:11

Yes you can adjust the air mixture. It’s called an air shutter. Gas furnaces, gas ovens, oil furnaces have air shutters you can adjust the amount of air to the burning process. Most manufacturers find anything under 100 PPM acceptable. I shoot for under 50. If you add too much air, the efficiency of the appliance drops. Always use your hood vent and if you can open a window as well even better. Especially on Thanksgiving or when your oven is on for a long period of time. Like he said a hood that vents to the outside is what you want. I think you can call your local gas company and they will come out and inspect your appliance for FREE.


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