I am concerned that HandiFoam, and other Fireblocks rated to Type V Residential Fireblocks are being used as high temp silicone caulk. I spoke with Becky at Customer Service for Handifoam (Fomo Products).  POLYURETHANE FOAM (Fireblock) is NOT RATED for continuous heat exposure above 240 Degrees F.  This was Verified by its MSDS sheet (see attached Doc and highlighted notes).  There is a bit of a discrepancy between FOMO Customer Service, and the MSDS. The MSDS states above 200 Degrees F product will decompose, but Customer Service Stated 240F. 

Fireblock is designed to provide an air barrier between spaces in case of fire, to ensure a certain burn time of the product before compromising the adjacent spaces. It is NOT designed to seal air spaces between single wall and B-Vent venting configurations where clearance to combustibles is of concern.

Here is a link that explains the purpose of the product.
Its a fancy label, that wrongly portrays a product to do something that it doesn't, coupled with the influence of Home Depot's knowledgeable home professionals, and the ignorance of John Q Public, the product took off beyond its expectations.
And just because I used FOMO PRODUCTS as the example, doesn't mean other like products are acceptable.  Polyurethane foam is polyurethane foam, IT BURNS.

I did leave out pg 6 of the MSDS because of the 5mb restriction on file size.  There was not any relevant information.

Just sharing my Research...
Let me know your thoughts,

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"The MSDS states above 200 Degrees F product will decompose, but Customer Service Stated 240F. "


The 240F is probably a slip by the rep. If the MSDS says 200, then that is what the company is prepared to support. The 240 may have been a test number achieved and discussed in house, but the company may want some tolerances to cover themselves, or they want to go with the worst of the tests that they conducted.

If someone is using the foam to bridge a gap larger than what fire resistant caulk can fill, then they are not doing themselves any favors. They need to mechanically or physically reduce the gap, and then use the caulk.

And a reminder about caulk-it is not designed for 3-sided adhesion. Only 2-sides are to be "stuck to". Be sure to use backer rod (or sand in floors) to fill a gap to the proper depth before using the caulk.

Even though retrofits are not new construction, it can be instructive to look at how the latest codes handle this.  Since the 2003 IECC and IRC the word 'fireblock" was re-defined.  So here are the three categories you should know about:

First is a Firestop.  A firestop is a material that has a set of directions, and if applied using those directions, has a fire rating for a certain amount of time - 1 hour, 2 hour, etc.  Cinder block, taped drywall, even cellulose insulation, have certain fire stopping applications, but they have to be used properly.  Firestop caulk requires the ASTM E814 certification.

Second is a Fireblock.  A fireblock is used to "impede the movement of smoke and flame", not to stop them.  There are no instructions that need to be followed to a "T" because these will never be firestop with a fire rating.  Each fireblock material is tested and assigned a number for how much fuel it contributes to a fire (how fast it burns) and for the smoke that is generated while it burns.  If the material has numbers that make it better than framing lumber, it may be allowed to be a fireblock.  All of the single part pressurized foams made in the US, regardless of color, is a fireblock.  Dow was the first manufacturer that hit on the fireblock idea about 2004, and they had the idea that making it orange would allow building inspectors to identify it better.  At the same time, their "Great Stuff" was also designated a fireblock through the code testing procedure.  Remember that the biggest hole the foam is allowed to fill is 1-5/16", this is because the expensive testing was done on this thickness, not any thicker.  

Third is a non-cumbustible fireblock.  This is the material that is put into areas that may may get hot, like next to a flue, but are not a firestop.  While not specifically spelled out, the basic non-combustibility certification is ASTM E136.  Silicone is also heat resistant, and the clear has the highest temp rating.  If it is colored, it goes down approximately with the darkness of the color, but only by a little.  Find out what your inspector likes if you think that this will be an issue.  He should not require E814 for fireblock - but as usual, pick your fights. 

Free standing single family homes have no code requirement for a firestop anywhere.  So single part foam and E136 caulk is all you will need to sleep well at night.  Extruded styrofoam, like Dow blue board, is not listed as a fireblock, however, once you cover it with fiberglass of cellulose, it is.

In town houses - attached houses with a common wall - the common wall must be a firestop with a specific rating.  If I beat a hole with a hammer in the common wall, I must fix it with firestop material with the same rating as the rest of the wall.  So a hole in a gypsum common wall might be fixed with a certain thickness of gypsum pieces, sealed with E814 caulk.  However, there is no firestopping required on the interior,inside the common wall, so fireblocks (even wood) are allowed to touch it.  So you can use fireblock foam touching the common wall - note that this is virtually ALL foams, but best to get a copy of the icc-es report for the foam you use.  In new construction

In multi-family with no property line - apartments and condos - you must use an E814 material as the units must be firestopped from each other.

We work in both new and existing homes and have standardized on these 3 material for both - single part foam, E136 caulk, and E814 caulk.  We also use plenty of  plain old acrylic latex for areas that need to be sealed that do not need fireblocking or firestopping

Hope this helps.

Very Much Thank You



I'm the Marketing Department Manager for Fomo Products and I would like to clear up the confusion on the temperature differences. Handi-Foam Fireblock Foam Sealant is for use in type V residential construction in vertical and horizontal penetrations between rooms and floors. Fireblock Foam Sealant is not intended for use in hourly rated assemblies. We do not promote our product as a firestopping product.


Whomever you spoke to in our Customer Care department was most likely quoting the technical data sheet when they said 240F degrees. This is the temperature for the cured foam product, whereas the MSDS is for the chemicals in the can and their boiling point is 200F degrees.


The Technical Data Sheet states that cured foam should not be exposed to temperatures above 240F. The MSDS is for the ingredients in the can as they are being shipped and during use. The 200F is the boiling point of most of the ingredients in their liquid form.


All of our products are for professional use only and not sold in big box stores. We agree that education and training are very important when handling and using these products.


I would be happy to discuss this with you further or answer any other questions you might have.



Leba Lualdi

Marketing Department Manager

Fomo Products



Thank you for your input, and the clarification.


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