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Cable trays and blazes

In the complex world of firestopping, the term "approved system" can mean different things to different people. Such ambiguity could end up causing inordinate grief for both contractors and structured cabling installers.


April 1, 2005  


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Any commercial building that is properly designed and constructed has fire-retardant security features. As an example, a one-hour rated fire wall in perfect condition will withstand the effects of a raging fire long enough for the people inside to get out with time to spare.

The problem is that the barriers have been compromised and sometimes damaged for many years by unregulated structured cabling installers across North America. They are directly responsible for negating the value of a building’s most important security asset.

It is a large problem and the time has come to repair past mistakes and make amends by learning more about fire-rated barriers. Contractors should seek out training on firestopping, establish a standard operating procedure (SOP) to avoid violations and get to work repairing fire rated barriers.

They should also:

Take pictures. If bidding on a cable installation, take digital images of the barriers you will penetrate and all violations as well. After presenting your cabling bid, ask for a consideration (as an addendum) of your SOP for firestopping the new cables.

Show images of what the barriers will look like when finished. Present the images of any violations and offer to repair the damaged fire rated barriers. You have, in effect, limited your liability with respect to the previous damage as well as made a good impression.

There are many new systems that have recently been developed specifically for sealing penetrations in fire-rated barriers made by installers as they route the latest in high speed communications cables.

With respect to how they work, these devices are essentially the same in that the two principal elements of a typical penetration system for the installer are the “intumescent” and the method of “bounding” the intumescent.

Intumescent caulk and putty are the active material of a firestop system. It will expand to form a type of insulation within the system to prevent passage of the smoke as well as the flame.

All intumescents will work about the same way. The key to a successful system is the method selected for “bounding” the intumescent.

As the term implies, bounding the intumescent can be done with sleeve systems, square or triangular metal boxes or even chicken wire for bounding putty pillows in a large cable tray penetration.

To be sure, installers will need to know a little more than firestopping theory.

Remember, if a blaze occurs in a building that you were involved with and there is loss of life or property, the lawyers of the victim’s families and the lawyers representing insurance companies will be calling on you.

The steps listed above are a culmination of issues derived from meetings with inspectors, architects, engineers, project managers and installers. Firestopping by the Numbers will work with any manufacturer-tested product.

My involvement in firestopping began when I developed a mechanical penetration system for structured cabling installers. During the development phase, I was amazed by some of the penetrations encountered in commercial buildings, schools and hospitals.

Consistently, the most difficult firestop issue always revolved around the cable tray.

It seemed to run continuously through fire rated barriers with reckless abandon. The holes created by passing the tray through the wall or floor varied in size and shape. It was as if a different person had planned and executed each and every hole, even in the same building, or on the same floor. There was no method to the madness.

So much so that it was decided that the cable tray penetrations were going to be too tough to handle as far as coming up with a unique offering. A decision was made to abandon R&D efforts on this type of penetration.

For the next three years, our company developed sleeves for retrofitting penetration violations and penetrators for new installations.

The systems are the accumulation of ideas and solutions from the cable installers’ perspective. All were well received by the cabling industry, but what about those pesky cable tray penetrations?

Firestopping employs methods that are tested and classified in the amount of time before a fire will pass through a rated barrier.

When our small company developed systems that passed through fire-rated walls, we had to send them to an independent testing laboratory to be tested. The cable tray industry has managed to sidestep firestop issues by just saying and doing, “nothing.”

The average architect or engineer will spec a cable tray and leave it up to a contractor to install it, most of the time with very little or with no reference to firestopping.

From what I have seen first hand in the field, the term “approved system” can mean many different things to many different people. Quite frankly, the term is ambiguous and often controversial when the time comes for the work of a low voltage installer to be inspected as cables are routed through fire rated walls and floors.

Many people think a tube of caulking is an “approved system.” The cabling industry has responded with new and innovative products. New methods need to be integrated in to the standard operating procedures of our craft. The practice of cable trays running through firewalls is, in my opinion, not a good method.

A simple and effective alternative would be mechanical systems that will allow cable trays to be stopped a few feet short of the fire barrier, the system installed and the tray picked up again on the other side of the barrier.

It is a little known fact that there are no proactive cable tray penetration classifications for trays to go through a fire barrier. I did not say “illegal,”I said proactive. In other words, the cable tray manufacturer did not go to Underwriters Laboratories Inc. or another recognized testing laboratory and say, “test this tray penetration for two hours, make the hole this size, use these pillows and compress this amount.”

Instead, they left it to the end user to retrofit whatever they ended up with. Those large holes will be a nightmare for the life of the building.

Maintaining them will be expensive and time consuming. The point is, we should stop it.

Mike Tobias is the founder and CEO of Unique Fire Stop Products, Inc. based in Robertsdale, Ala. He can be reached via e-mail at mtobias@uniquefirestop.com.

Firestopping by the Numbers

1. Establish the hourly rating of the wall: All barriers are tested in increments of time. Be sure to check the barrier for all applicable ratings such as F – T – L. Once the rating of the barrier is established, seek a tested penetration system to match or exceed the barriers rating. Manufacturers will help you with this task.

2. Select and acquire the systems listing: Pay close attention to the cable load limits, the fill procedure and packing requirements if any. Place a hard copy of the listing in the job file for future reference. Have it on hand for inspection.

3. Plan the Installation: Refer to cable load charts based on the allowable percentage of cable load allowed in the system you have selected. You might consider the possibilities of adding cables at a later date and future-proof the penetration. However, do not make a hole any larger than necessary as a large hole is much more difficult to seal than a series of smaller holes.

4. Seek pre-approval from those who have authority to enforce compliance: Do not skip this step and do not roll your eyes, just do it. Find out who you will be inspected by and submit your systems information for pre-approval. Remember, it is not “approved” unless the inspector says it is.

5. Follow the manufacturers’ assembly instructions: Cable load limitations are the most commonly violated portion of a through penetration system installed today. Pay close attention to the limitations in the tested system and consult with the manufacturer when the situation requires a deviation. Many manufacturers can perform an Engineering Judgment (EJ) to cover you.

6. Digitally document your installed system: Label and alpha-numerically identify each penetration system. Many systems will come with documentation and warning labels for you to fill out and adhere to the wall next to your system. Be sure to take a digital photo from a short distance away as well as a close up of the label. Submit these photos to your customer as their Firestop Certification and always keep an electronic version.