Confused about sealing around firestop

[MDfireplaceGuy]

Preparing to install my Quadra-Fire fireplace, and I'm confused by this statement in the manual:

Warning! Risk of Fire! Do NOT seal area between firestop opening and chimney pipe except where they enter the attic or leave the warm air envelope of the home (use 600° F sealant).

Based on my understanding of this statement, I'm not sure where I need to be careful to NOT seal...

My 2x4 framed chase runs outside the house from the first floor, past the second floor and attic space. The original fireplace installation had a piece of OSB between the first and second floors, with a firestop in between (no framing). I'm adding 2x8 framing with plywood on top and will insulate above. Is the area below this considered the "warm air envelope"? If so, then I should apply sealant between the firestop and the chimney pipe, right?

 

[webby3650]

That’s how I read it.

 

[MDfireplaceGuy]

So, what area are they warning me about NOT sealing?

 

[webby3650]

Often times the firestop is within the envelope of the home, in a multi floor interior chase. In this case, the firestop would not be sealed. If the firestop is your ceiling/attic, then it would be sealed to prevent air infiltration.