# Has anyone used the the "Great Stuff" "Fireblock" for sealing around their pipes?



## eyeaml337 (Jan 3, 2009)

So my uncle (who is a general contractor and a smart guy) used this stuff to seal the air gaps around his wall thimble and said that its the best stuff he has ever used.  He then used it on mine.  It occurs to me after ... maybe I should have done some research.  It does say its fireblocker and the guy at Home Cheapot (read: unreliable source of information) says that not only has he used it on his stove but that its is "the best dang stuff for sealing around the pipes because it is also a fireblocker so the wood doesnt absorb that heat and will close all the gaps!"

So, anyone used it?


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## eyeaml337 (Jan 3, 2009)

he can does say that it is combustible but so far (out of paranoia) i have been checking every 20 minutes to make sure there is no smoke or anything around the pipe.  i also took some and laid a 6" long bead on the pipe and then another big globby one on another section of pipe just to make sure.  pipe gets hot but i have no idea how hot.  so far its been a whole bunch of nothing.  i have some other stove "issues" so im keeping it running as long as i can and as hot as i can.  and checking it constantly.

i mean logically if it doesnt ignite within 4-6 hours ... it shouldnt period right?


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## crausch (Jan 3, 2009)

I used this spray stuff in my install also. I was going through an existing 8" hole in my wall from a previous wood stove install. I installed the thimble for the pellet stove and used the Fireblocker spray foam to fill in the gap that was left between the thimble and the 8" hole. So far there has been no problem and I don't expect any.

The outer ring on the thimble is your heat shield. It retains the proper clearance from your actual pipe so that combustionables can go against the outer ring. You should not have any problem as the heat shield should not get hot enough to cause any problems. If it does, then you have a definite problem with your stove. Also, even if your outer thimble ring managed to get very hot, your in good shape because you have fire retardant material behind it.


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## GVA (Jan 3, 2009)

The original would flash if in direct contact with a pipe.
Had a friend who was a firefighter/hvac guy he told me about someone putting that stuff around a furnace pipe and it degrading and combusting creating a fire.....
Now that said I would think it's alright around the thimble but not on the pipe directly.  They do not give the flash point of the cured stuff on the MSDS but it did say that if it does catch fire it will release some nasties into the air like isocyanide....


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## eyeaml337 (Jan 3, 2009)

i shut it off overnight (damn im cold now) and fired it back up this morning at about 10am EST.  Even holding a lighter to a chunk of the stuff it will catch and then go right out.  so i think its all good.  I have also talked to a few people who did the same thing and had no problems.  Fun times!


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## Devo (Jan 3, 2009)

You should know how fire block caulking works in order to know where and when to use it. When exposed to extreme high temperatures, such as a fire, it expands and seals any gaps even though the caulk may have been used to seal the gaps. It's just the way it works though. It expands so that it is highly unlikely that gaps exist during a fire.

If you wanted to prevent a flame from spreading from one sealed location to another, such as a pipe penetrating one space to another, I'd use it in a non-visible location, because it's typically red or orange. For example, the attic side of a penetration. 

On the other hand, if it was just a typical penetration and I was caulking the pipe at a visible thimble joint, I'd use black high temperature caulk.


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