Safe Cabling Through Firewalls

The need for fire stopping is said to have started back in the early 1970s and ’80s from a nuclear plant and a large Las Vegas casino fire that caused many fatalities. Today, new technologies have been invented and designed to help system cable installers with the running of cabling through fire barriers.

Mike Tobias, CEO of Unique Fire Stop Products in Robertsdale, Ala., comments, “The single most important fire-stopping issue today is apathy. Increased training and AHJ inspections are needed. An improperly sealed barrier has the culprit’s name attached to it for the life of the building. If the building should burn down 10 years after XYZ company blew holes in the firewalls, they will be after XYZ.”

This month, I will give you some fire-stop cabling strategies and techniques to help keep you on the straight and narrow. Simply put, fire-stop techniques are not being practiced. Additionally, the inconsistency of code compliance inspections by authorities having jurisdiction (AHJs) has compounded the problem.

Remember, It’s the System
One of the most important things an installer needs to remember is that when applying a fire-stop method they are applying more than just some caulk or putty to fill the annular space around a cable. The technician is applying a proven containment system in which all components (putty, mortar, sleeves, pillows, etc.) have been tested together in simulated fires by organizations such as Underwriter’s Laboratories (UL 1479).

These fire-stop systems are specified to provide protection for a specified number of hours per ratings for fire (F), temperature (T), air/smoke leakage (L) and even lately water (W) penetration. Remember: It is very important that these fire-stop systems by applied per the specific instructions of the manufacturer.

Where to Install a Fire-Stop System
While new systems will often have fire stops specified, what is a dealer to do on a retrofitted cable run? Sometimes you can check to see if the doors are fire rated or, better yet, get the building owner to sign off on identifying the walls you will be going through. Make sure you know where and what you are going through. Give serious consideration to having a preinstallation meeting with the local AHJ.

If you find yourself having to install a fire-stop system after a cable installation, check out products like the “Split Sleeve” systems from Unique Fire Stop Products.

What Fire-Stop System to Install
“What type and size of system do I install?” First, you must determine the rating of the firewall to be penetrated.

Some guidelines are: a 5/8-inch-thick gypsum dry board equals a half-hour fire rating; cinder block is typically two hours; block with concrete is three hours and rebar is four hours. Some walls with a single sheet of fire resistant sheet rock may be classified as a smoke barrier, but they should be treated as a firewall to seal from smoke penetration.

When running cables through a fire stop, one important specification is cable load. Installers may have run across similar specifications when figuring how much cable to run through conduit per the National Electrical Code (NEC). Cable load will vary slightly per fire-stop manufacturer, but the rule-of-thumb is less than 50 percent for a two-hour-rated penetration.

The formula for estimating a cable load is (cross area of cables) X (number of cables) divided by (area of opening). So if we had a 4-inch opening with 21 5/8-inch cables, we would have (0.307 square inches) X (21 cables) / (12.57 square inches) = 51 percent cable load.

This may mean that you have slightly exceeded the UL specifications for the fire-stop system chosen and would have to make two openings for the cabling to penetrate the firewall or floor. Don’t forget to allow for future cable as well.

Many different types of materials are specified for filling up the annular space around each cable. They include caulk, putty, wrap strips, seal bags or pillows and loose batting. They are typically made of either an intumescent or mineral wool material.

Intumescent sealants expand when applied to the heat from a fire. This allows the sealant to compensate for the shrinking and destruction of cable jacketing caused by a fire, and maintain the integrity of the fire-stop seal for the fire time period specified.

Important Fire-Stop Sealant Facts

  • Sealants are not generic; each manufacturer has tested them with labs like UL for specific in stallation and ratings.
  • Many sealants are actually smoke sealants and are to be used only as part of an overall fire-stop system.
  • Confirm sealant elasticity, espe cially in earthquake regions such as the southwest U.S. Sealant should withstand building move ment without causing any cracks.

Many of the fire-stop system manufacturers referenced in this article have calculation tools and instructions for figuring the correct fire-stop system per the number and size of cables being run, and the rating of the wall. This being said; it is always important to remember that even specified systems are not truly approved until the AHJ says so.

Key Steps to Fire-Stopping Cables
Recently, Unique Fire Stop’s Tobias outlined some important steps for fire-stopping cables in a Building Industry Consultants Service Int’l Inc. (BICSI) newsletter.


  • Establish the hourly rating of the firewall
  • Reference the thickness and type of wall or floor
  • Select and acquire the systems listings
  • Pay attention to cable load limits
  • Have documentation, including MSDS, for inspections
  • Plan the installation
  • Use manufacturer specification calculations
  • Allow methods for additional future cable
  • Seek preapproval from AHJ
  • Follow manufacturer’s assembly instructions
  • Cable load violations are the most common
  • Check specs when adding cable to an existing fire stop
  • Manufacturer may be able to per- form an “engineering judgment” to cover you
  • Digitally document your in stalled system
  • Label and alphanumerically identify each penetration system
  • Take a time-dated digital photo of your finished fire-stop installa- tion to prove your original config- uration as others may add cable and modify it; may also help es- tablish residual work

Many Training Resources Available
Fire-stop training is still seriously needed for many installation companies. While industry standards have been developed through the years, nationwide consistency of installations and inspections is still a big challenge. Additionally, organizations such as the Fire Stop Contractors Int’l Association ( and BICSI have committed to major programs to train AHJs across the U.S.

Listed below are some fire-stop product manufacturers that provide valuable product and training information. I was especially impressed with Unique Fire Stop Products’ free online training video and certification program.


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