Firestopping, Part 2

The design of firestop systems is quickly becoming a highly complicated and highly specialized area. A particular building design may have the need for several different firestop systems to cover all the possibilities. One often sees plan sets that contain one or more sheets dedicated to firestop system details.

The construction side of the equation is getting equally complicated and specialized. It used to be that if you as the subcontractor made the penetration it was your job to firestop. Increasingly, this model is no longer working. Greater numbers of general contractors are beginning to look for specialty subcontractors who can handle a project’s firestopping needs.   

The 2015 edition of UL’s Fire Resistance Directory contains a complete listing of all of their listed firestop systems in Volumes 2A and 2B of the set. Each listing is provided with a detail containing call-outs for each required component in the system. There are approximately 3,000 pages dedicated to through penetration firestop systems in the two volumes. 

If you are not inclined to purchase the hard copy, you can find information on any of the thousands of listed firestop systems at Though the database is extensive and can be searched, it may be difficult to find what you need unless you are able to narrow the search. To do this it would help to have some information on the UL numbering system for through penetration firestopping. Let’s take for example the UL system number C-AJ-1002. The first letter indicates the general type of penetrated item: W-  Wall Penetration; F – Floor Penetration; and C -  both Floor and Wall.

The second letter of set of letters provides more specific information on the penetrated construction:

A - for concrete floors less than or equal to 5 inches thick (minimum)
B - for concrete floors greater than 5 inches thick (minimum)
C -  for framed floors
D - for deck construction
E to I – not used
J - for concrete or masonry walls less than or equal to 8 inches thick (minimum)
K - for concrete or masonry walls greater than 8 inches thick (minimum)
L - for framed walls
M - for bulkheads
N to Z - not used

The numbers describe the general type of penetrating item:

0000-0999  None
1000-1999  Metal pipe, conduit, or tubing
2000-2999  Non-metallic pipe, conduit, or tubing
3000-3999  Cables
4000-4999 Cables in a cable tray
5000-5999  Insulated pipes
6000-6999  Miscellaneous electrical penetrants
6000-7000  Miscellaneous mechanical penetrants
8000-8999  Groupings of penetrations containing any of the above
9000-9999  Not used

So, our example system, C-AJ-1002, would be a through penetration fire stop system that can be applied to a wall or floor penetration, penetrating  concrete floors of 5 inches or less, or penetrating a concrete or masonry wall of 8 inches or less, penetrated by metal pipe, conduit or tubing.  
I do find the website helpful when reviewing designs or submittals to confirm that the correct systems are being applied. As a design aid, the UL directory and website are a bit too cumbersome for me.  

If you are looking for a firestop system for a specific application, a good place to start is with the firestop product manufacturers. Several of the major manufacturers have websites with firestop system selection guides that can help you find a system that works best for your needs. 

Another valuable service offered by some of the major firestop manufacturers is the engineering evaluation. In the event your particular application cannot be met by a specific listed system, the product manufacturers can develop a system, which though not listed as a system, can be deemed to meet the requirements based on engineering judgment. This usually involves using listed components to make up a complete system.  

Certain jurisdictions now require that firestopped penetrations be provided with identification labels. These labels provide information to facilitate firestop maintenance, repair and inspection. Information would include date of installation, listed system number, hourly rating, and the name of the installer.  

Starting with the 2012 edition, the International Building Code requires special inspection of firestop systems for high-rise buildings and buildings with an assigned Risk Category of III or IV (Section 1705.17 of IBC 2015). Section 1705.17.1 requires that these inspections be conducted by an approved inspection agency and that these inspections be performed in accordance with ASTM E2174, Standard Practice for On-Site Inspection of Installed Firestops. This standard requires the inspector to observe the installation of at least 10 percent of each type of firestop system. If the installation cannot be observed then destructive testing of 10 percent of the completed installations shall be performed.

Seems like gone are the days when the plumber carried a tube of red firestopping in the tool chest. 


Samuel S. Dannaway, P.E., is a registered fire protection engineer and mechanical engineer with bachelor’s and master’s degrees from the University of Maryland Department of Fire Protection Engineering. He is past president and a Fellow of the Society of Fire Protection Engineers. He is president of S. S. Dannaway Associates Inc., a 15-person fire protection engineering firm with offices in Honolulu and Guam. He can be reached via email at

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