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Article 14


ACP ALERT - Fire Safety with certain Cat 5 Cables

Updated June 1, 1998

Potential Fire Performance Safety Problems With
Certain Types of Plenum Rated Category 5 Data Communications Cable

This alert is being issued because of questions concerning the long term fire safety performance of "hybrid" Category 5 plenum cables which use new insulation compounds as replacement for 100% FEP Constructions.


Data communications cable installed outside of metal conduit in concealed air handling spaces such as air return plenums must meet low flame and low smoke requirements as specified by the NFPA (National Fire Protection Association). Meeting these requirements means the cable can be listed as "CMP" (Communications-Plenum) and is acceptable for installation in building plenums. Until recently, all Category 5 CMP listed cable was 100% insulated with FEP (fluorinated ethylene propylene). You may be more familiar with the DuPont trademark Teflon® FEP.

The rapid growth of LANS and data communications cabling led to a temporary shortage of FEP resulting in the use of substitute insulations consisting of flame retardant polyolefin compounds (e.g. polyethylene and polypropylene). Cable designs using these substitute insulations are generally referred to as "hybrid constructions", in which only two or three of the four pairs are insulated with FEP. These are known as "2x2" or "3x1" designs, respectively.


If cable being installed is "CMP listed", what's the problem?
There are three potential problems:

  1. The cable may NOT, in fact, be code compliant.
    Certain hybrid cable constructions, such as "2x2", marginally pass fire safety performance tests but variability in insulation compounds and the cable manufacturing process could mean the CMP rating is not consistently accurate. UL (Underwriters Laboratories), the leading test and listing agency for the cabling industry, is so concerned about this potential compliance problem that a special meeting was called April 15, 1997 to review data and discuss the issue.

  2. The plenum rated (CMP) cable you install today may not be plenum compliant tomorrow.
    The long-term stability, or retention of fire protection properties of hybrid cables, is in question. Unlike FEP, the new substitute insulations are mixtures or compounds of various materials. Since these do not have a proven record of long term performance, aging and stability tests at elevated temperatures found in plenums are needed to ensure that fire protection properties do not change with time.

  3. More fuel load is building up in plenums due to hybrid cables.
    Although new olefin-based compounds may meet the flame and smoke requirements for installation in plenum areas, these materials have very high fuel load and are defined in NFPA 90A as "Combustibles". Expect fire safety engineers and codes authorities to rigorously examine what may be an inconsistency in the codes, possibly leading to code revisions.


  1. Specify Category 5 plenum cable insulated 100% with FEP. This cable construction is endorsed by the ACP.

  2. Use the ACP cable specification that requires 100% FEP insulation.
    A complete cable specification, including manufacturers and part numbers for Enhanced Category 5 (Level 6) plenum cable is available on this web site. The specification exceeds the minimum requirements of current TIA (Telecommunication Industries Association) and ICEA (Insulated Cable Engineers Association) standards.

  3. Stay informed. Routinely check this web site. ACP will load key educational and information materials on our web site from a variety of sources.


The ACP Alert dated 3/27/97 warned of potential fire protection problems with certain types of Category 5 (CAT 5) plenum cables. These cables use new insulation compounds as a substitute for FEP*. They are typically identified as "2x2" or "3x1" composite constructions since only two or three of the four pairs use FEP.

The Alert also reported that UL (Underwriters Laboratories), the leading test and listing agency for the cabling industry, was so concerned about this potential compliance problem that a special meeting was called on April 15th. Information presented at this meeting by UL, and others, confirmed there is a problem and that it is more severe than expected. This update is intended to provide you with a summary of the outcome of the April 15th meeting at UL; to provide you with market information to guide your procurement of CAT 5 plenum cable; and to assist you in avoiding potential fire protection and legal problems.


UL reported on follow up tests to check whether recent production samples of CAT 5 CMP listed cable met the requirements of the UL 910 test. (Initial production of these cables met the flame spread and smoke limits of UL 910 and qualified for CMP listing at the time.) Ten (10) of the Twenty-one (21) samples from 19 manufacturers failed the test, confirming the wide variability in fire protection of composite cable designs.

UL also proposed formation of two committees to study the problems affecting the fire safety performance of plenum cables. These committees will investigate such things as:

  • A "listing program" for insulation compounds
  • Improvement of the UL follow up testing program
  • Marking cables (i.e. "4x0", "3x1", "2x2" etc.)
  • Effects of aging on fire safety performance

It does not appear that UL plans to issue a cable "recall" or public warning at this time.

ACP strongly advises cabling contractors and end users to take action to avoid potential fire protection problems and possible legal and insurance problems.


Despite the absence of a public disclosure of the problem by UL, cable manufacturers and distributors are taking action to resolve it. Some cable manufacturers have responded by upgrading production to only "4x0" constructions that are 100% FEP insulated. Others are still producing "3x1" and "2x2" designs because of intense price competition in the low end of the market. Based on the variability in fire protection as reported at the April 15th meeting at UL, you should question the suitability of these cable designs for plenum installation. Producers of composite cables will also supply "4x0" cable upon request.

According to our sources, Anixter and Accu-Tech have been proactive and will soon be stocking an all FEP cable (insulation and jacket) for those looking for the highest level of fire protection. We may see more demand, and stocking by distributors, of "4x0" cable as "2x2" and "3x1" cable inventories are cleared out through aggressive pricing. There are signs that some "dumping" may already be occurring.

The allure of low price could spell trouble. The modest premium for "4x0" constructions is a small but valuable investment in protection. We recommend you shop for price but require quotes on "4x0" design. The ACP endorsed model specification for Enhanced Performance CAT 5 (Level 6) plenum cable with limited combustible wire insulation is based on a "4x0" design. It is recommended for CAT 5 plenum cable procurement and is available on this web site.

Check this site regularly for further updates on fire protection and information on high performance cabling systems.

* FEP is commonly known by the Dupont Trademark Teflon®


The fire safety problem discovered with certain plenum rated cables appears to be under control. This problem, and what to do about it, was discussed extensively in the ACP Fire Safety Alert and subsequent Update. In summary, the above ACP Alert reported that UL found an unacceptably high failure rate (48%) in their follow up test program for "CMP listed" (plenum-rated) cable. The majority of cables failing flame and smoke tests were constructions using insulation substitutes for FEP.

Since our last Update (May 2, 1997), UL has responded by suspending CMP listing of cables which fail and have tightened their quality assurance programs. In a June 10th, 1997 letter from UL to cable manufacturers using their follow up testing service, UL stated:

"Authority to label product with the UL Mark will be suspended immediately in the event that the product samples tested under UL's Follow-Up Service do not conform with the UL 910 Standard. This measure is also applicable to those products for which samples have previously been tested, and have not currently been found to comply with the requirements. In all instances, labeling shall resume only after the manufacturer submits and acceptable explanation for the nonconforming results, and additional production samples are tested and found to comply with ULs' requirements."

As a result of UL's actions on this fire safety issue, and other developments, most cable manufacturers formerly producing cables using substitute insulations for FEP have changed most, if not all, of their plenum cable production to 4x0 100% FEP insulated designs.

ACP will continue to track this issue and provide further updates as necessary.

Check this site regularly for further updates on fire protection and information on high performance cabling systems.

ACP Fire Safety Alert UPDATED June 1, 1998

The plenum cable fire safety issue, reported in ACP's Fire Safety Alert, generated widespread attention throughout the cabling industry and fire science community.

Many mixed pair insulation cable designs have been taken off the market in favor of returning to the industry standard 4x0 100% FEP. FEP and 4x0 cable are available in good supply for CAT 5, Enhanced CAT 5 (CAT 5e) and Anixter Levels 5, 6, 7 performance requirements.

UL (Underwriters Laboratories) and major fire safety agencies have responded with very active programs to assure stringent testing and compliance procedures are followed. Following is a brief synopsis and update.

  1. UL's March 20, 1998 bulletin proposes... "...a program of analytical tests to characterize commercial and proprietary jacket and insulation materials used in the construction of plenum cables listed by UL. The information obtained is for use in periodic materials testing at UL to ensure the consistency of these materials. Improved consistency is the aim." Also, to strengthen it's relationship with the wire and cable industry and deal with fire safety and other issues, UL announced the appointment of Mr. Steve Galan as Coordinator for UL's Wire and Cable Sector and Associate Managing Engineer of the Wire and Cable Department.

  2. In their May 8, 1998 Bulletin, UL proposed "...a revised description of the plenum flame test to update the UL 910 standard. There are no changes in the test, just in the wording and illustrations to more completely and accurately describe the test as it is conducted at UL Northbrook." This revision would provide a more detailed reference documentation of UL 910 test equipment, operating conditions and requirements, and maintenance procedures. UL 910 is the test procedure used to qualify cable for CMP listing which allows installation in plenum areas.

  3. The NFPA (National Fire Protection Association) Fire Test Committee met on April 30 and May 1, 1998 to develop a revision to NFPA 262 to align it with the above mentioned UL 910. The objective is to have uniform test methods and procedures.

  4. At a May 21, 1998 meeting, the NFPRF (National Fire Protection Research Foundation) instituted a program to harmonize the fire testing of plenum communications cable on an international scale. A $300,000 "round-robin" program was initiated. Dr. Tom Chapin of Lucent was appointed Technical Director. Participating in the round-robin test program are:

        • UL Northbrook
        • ETL Testing Laboratories (ITS/ETL)*
        • Loss Prevention Council (LPC), UK
        • British Research Establishment/Fire
        • Research Station (BRE/FRS), UK
        • Japan Electric Cable Technology Center, Inc.
        • (JECTEC)

These intense testing and harmonization programs are positive developments but in the meantime... "caveat emptor." Let the buyer beware is prudent advice.


For those of you who procure or install cable - be wary of substitute insulation materials. We recommend the following:

  1. Know what you are buying. Insulation materials make a difference.

  2. Ask for 4x0 100% FEP designs for plenum cable for fire safety protection and proven performance.

ACP will continue to track this important fire safety (LIFE) issue and bring you updates when important developments occur that you should know about. Stay tuned and be sure to check this website regularly!

*The ETL mark is owned by Intertek Testing Services (ITS)


  Friday, July 18, 2003
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