Myth #8 - CO
is only caused by incomplete fuel combustion. (Wrong!)
Well, technically I guess Myth #8 is "correct", sort
It's really like arguing about whether you got 12
or 14 inches of rain. If there's a foot of water in your basement, what difference does it
Here's a scoop for you.
While there is NO such thing as perfect combustion, natural and
LP gas come pretty close.
Gas furnaces and gas stoves run for decades without building up
much soot or ash. Their products of combustion might include some unsavory gasses, but that's NOTHING
compared to what comes out of your vehicle's exhaust pipe, or some factory chimneys.
Natural Gas Burns Clean
For the sake of argument, let's examine an atmospheric vent gas
Atmospheric vent means the furnace
depends on warm air to rise and carry the products of combustion through the flue and out of the
house. There's no powered draft inducer to push or pull air through the heat exchanger. In the
vernacular they call this a "positive draft in the flue".
If you misadjust the flame on the gas burners by closing
down the primary air shutters, you'll see an increase in carbon monoxide in the flue. If you crank
the gas pressure to the burners way up, you'll over fire the furnace and see more CO in the flue gasses.
At any stage along the way you can say that the CO was caused by "incomplete" combustion. But, because the CO
levels are relatively low (still under 400ppm) and they are being carried out of the structure by the flue, there
is NO immediate reason for alarm. Putting it another way, incomplete combustion does not necessarily lead to
CO poisoning or CO health problems.
Now, with a perfectly adjusted furnace (with 0ppm CO output)
there is almost complete combustion. But, if a roofer rests a stack of shingles on your flue cap
(on the roof) and crushes it, guess what! (Same situation if the bird screen on the flue cap is clogged with
cotton wood, or birds build a nest in an open flue cap during the summer.) You're well
adjusted furnace will soon start producing very high levels of carbon monoxide because the flue is
blocked. Given some time, the CO will migrate into the home and that's when real problems can
Is it the furnace's fault? Nope! Is there
"incomplete" combus-tion? Yep! Did the "incomplete combustion" cause the
"Incomplete combustion" is a symptom!
It means go find out what's really wrong!