Boiler flue connection to chimney

[jtfoxman]

It seems like I've been living on these boards lately with all my questions but here is another.
My gas fired boilers flue pipe connects to my chimney but I noticed tonight that i can move the flue in and out of the chimney and 1/8" or so. The seal around the flue when it connects to the chimney is not air tight which allows the flue to move. Should I seal this connection up with something? It looks like they used some type of concrete spackle to seal this joint the last time they cleaned the chimney last year. I read that this is ok since it creates some type of updraft so it doesn't have to be airtight, but i'm a little concerned about this. I do have CO2 detectors in the house.

[paul52446m]

It seems like I've been living on these boards lately with all my questions but here is another.
My gas fired boilers flue pipe connects to my chimney but I noticed tonight that i can move the flue in and out of the chimney and 1/8" or so. The seal around the flue when it connects to the chimney is not air tight which allows the flue to move. Should I seal this connection up with something? It looks like they used some type of concrete spackle to seal this joint the last time they cleaned the chimney last year. I read that this is ok since it creates some type of updraft so it doesn't have to be airtight, but i'm a little concerned about this. I do have CO2 detectors in the house.

In most cases the air would go into the chimney around the pipe, but we usually seal it up because it could cause the chimney not to draft as good.
If you go to a hardware or wholesale house, you can buy some furnace cement to put around the pipe. Furnace cement take the heat with out cracking out so bad. The boiler can be fired right away , it dyes slow.
Later Paul

[jtfoxman]

Thanks Paul! Appreciate the help.