more questions about my gas furnace - CO leaks

After poking around the vents today, doing more work to insulate and clean up before winter I noticed that the vent stack on my furnace is for the most part coated in a white fine powder material, as well as rust flakes. I understand from reading about CO, that the white powder indicates CO problems.
But what does that mean, does it mean that the vent is leaking CO, or does it indicate the furnace is venting excessive CO (maybe burning inefficiently due to age)? The powder is only forming on the joints between pipes, which to my mind says exhaust gas leakage.
Just for reference my furnace is 23 years old, and none of the venting joints are sealed.
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The "white powder" is residual salts left from the water vapor that condenses within the flu [chimney] pipe. This water vapor is the result of burning natural gas. An abundance collects inside the flu piping, and condenses to water. When the water finally dries, it will leave a residual salt. Which by the way has the relative same pH as a glass of red wine [generally not exactly.] It does not mean you are leaking carbon monoxide, although, there is some carbon dioxide leakage occurring and is likely minimal.
What you don't want, is the flu piping to rust through, and allow excessive amounts of "products of combustion" leaking under your home or in your attic.
Seek the advice of your friendly neighborhood licensed furnace repair guy and have your heating unit inspected annually.
--
Zyp
"Eigenvector" <m44 snipped-for-privacy@yahoo.com> wrote in message
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Eigenvector wrote: ..

Any qualified professional should be able to do it.
If you don't already have them, now is a good time to add CO detectors in you home.
--
Joseph Meehan

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I will,
BTW: I'm gonna have to start talking to my buddies at the gas company more often. I mentioned the white powder to them and first thing out of their mouth was - furnace is short cycling, too large a unit for the house. I mentioned calling in an HVAC person, which I still am, and they cautioned me that the HVAC person will use the white powder as an excuse to sell a new furnace. They still recommended putting a CO detector at the thermostat.
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Eigenvector wrote:

They gave you good advice.
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Joseph Meehan

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Eigenvector wrote:

Let me add to my last response. A good professional would not use anything for an excuse to sell you something, but there are plenty that are not good who would.
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Joseph Meehan

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