Originally Posted By: ajalowsky
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Originally Posted By: Aimee Jalowsky
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Ok, I know the answer but I’m not sure how that works. Anyone care to explain a little?
Originally Posted By: bkelly2
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I’m thinking in my all electric home CO won’t be a problem either way.
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“I used to be disgusted, Now I try to Be amused”-Elvis Costello
Originally Posted By: rlind
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Aimee,
In a house with forced air heat, for example, there is a dischrage for the carbon monoxide produced by the heating fuel (typically a chimney). If there is negative air pressure, the air pressure in the house is lower than outside the house. Since air pressure seeks to be stable, the carbon monoxide filled air from the chimney will be drawn back into the house.
It is a potentially deadly situation.
In new construction where the house is sealed tightly from air infiltration (for example), excess air discharge from a house due to exhaust fans being on is one possible cause.
Is that a clear reply?
Originally Posted By: kelliott
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air flow situation, the air pressure inside the house is less than outside, so air is flowing into the house, instead of being constantly forced out. Two things happen. Exhaust air no longer flows UP the furnace and water heater flues, but is forced back down into the basement, or furnace closet, where it is circulated throughout the house.
This “backward” pressure also means that the air does not flow over the burners properly, so there is an imbalance of air pressure in the burn chamber, resulting in a flame that is being robbed of oxygen, so it is not burning the gas completely. This is what creates the carbon monoxide. Carbon monoxide isn’t just any and all fumes off the burner, but it is fuel that is not completely burned. A furnace or water heater should not normally produce carbon monoxide in the exhaust. IF there is carbon monoxide present in the exhaust, it is because the furnace isn’t burning properly. So when you have backpressure, you not only are forcing the exhaust back into the living area, but you are also creating an improper burn, so that carbon monoxide is created in the exhaust, making it a dangerous house!
So there always needs to be a way to balance the air so that the pressure inside the house is always a slight pressure, or positive air flow, forcing combustion air to flow out of the house. If you have a CO tester with a tube, you should put it up into the exhaust bonnet and take a reading. You shouldn't have a carbon monoxide reading. If the furnace is producing CO, it's not burning right and should be written up. If your CO tester doesn't have the tube however, don't try to take an exhaust reading, as I understand that the exhaust heat will burn out the sensors on some of the handhelds, and I'm told that most of them void the warranty for that.
Does that help?
Originally Posted By: kelliott
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For more CO info: http://www.cdc.gov/co/faqs.htm
Originally Posted By: Aimee Jalowsky
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Wow, Thank you for all your explanations. I can only imagine what happens when an inspector needs help! You all are great!
Negative is obviously the answer. 
Originally Posted By: pbolliger
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To add to Keith’s excellent info.
The ratio of air to natural gas for a "complete burn" is a 10:1 ratio. Ten parts air for every one part natural gas. The products of combustion are also moisture and heat. If an inspector sees heavy rust around a natural draft appliance draft hood along with particles and that funny Aldehydes smell, the evidence is pointing to a problem. An orange flame is a major sign of a lack of combustion air for a natural gas burning appliance. Lack of combustion air is one of the biggest problems I see with some home remodels and some basement DIY'ers finishing off and closing up the FAU /WH in a closet.. 