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KatieAK 04-12-2010 12:24 AM

Can I use this sealant (3M FD150+) on Class B flue?

I'm air sealing in the attic around the Class B furnace vent/flue (currently an open chase), which will include using roll metal flashing to create a 'block' around the pipe. I know that I need to use special fire-rated caulk to seal the seam between the sheet metal and the pipe. I have a tube of 3M Fire Barrier FD 150+ Sealant on hand (got on clearance before I knew I was doing this project) -- and am wondering if I can use it for this application. I'm no expert on fire code, so thought someone here might be able to help me decipher the product description, which follows:

[From the 3M website:]
3M™ Fire Barrier Sealant FD 150+ -- Acrylic latex caulk used to firestop metal pipes and cables through concrete or gypsum and for use in dynamic head-of-wall systems.

Designed primarily for sealing penetrations for non-combustible penetrants. 3M™ Fire Barrier Sealant FD 150+ has been tested and approved for single metallic pipe penetrations, common electrical and communications cable penetrations, as well as multiple penetrants through both masonry and gypsum wallboard constructions. 3M™ Fire Barrier Sealant FD 150+ has also been tested for use in fire rated construction joints.

Here's a link to the product spec PFD:

Now, I know I wouldn't be using this for concrete or gypsum, which are the materials referenced in the product description... but, the actual tube says "Bonds to most common construction materials." -- I'm wondering if this would likely apply to sheet metal?

The description above says it is "for non-combustible penetrants". Does a Class B duct (meaning, as I understand it, that we have two smaller pipes running inside the larger/outside duct - it's not the direct flue/vent pipe on the outside) fall into this category?

Any knowledge out there as to if this is the correct/code-compliant product for our application? I'd love to not have to run back out for other stuff (and save the $, as this was a great deal), if this would work.

Thanks much!

COLDIRON 04-12-2010 05:35 PM

You might want to post this under HVAC the guys over there know all about that kind of stuff. RE: Chimneys, class B pipe, heat, etc.

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