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
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
Seek the advice of your friendly neighborhood licensed furnace repair guy
and have your heating unit inspected annually.
"Eigenvector" <m44 email@example.com> wrote in message
Click to see the full signature.