blue flue

[kenny chaos]

The top six inches or so of my stainless steel flue pipe has recently turned blue. I got to thinking that this flue may be thirty years old and I wonder if it could breakdown (?) in that amount of time. It was existing and I'm only guessing when I say it's double wall insulated.
Any reason for concern?
Thanks-
Ken

 

[n6crv]

If it just started turning blue now that you are burning, it is from the smoke getting some downdraft. I also have some just starting to show. Last year I had about the top 4 in. blue but it washed off this summer.
Don