Communications Cable Fire Performance Hierarchy
Fred Dawson
The Chemours Canada Company
Mississauga, Ontario, Canada
905-281-4577 · Fred.C.Dawson@Chemours.com
Gerald Lee Dorna
Belden Inc.
Richmond, Indiana
765-994-9963 · Gerald.Dorna@Belden.com
Stanley Kaufman, Ph.D.
CableSafe, Inc.
Dunwoody, Georgia
770-394-4152 · CableSafe@Bellsouth.net
The Code has a similar hierarchy for optical fiber cables. It only
has three levels since there are no limited use optical fiber cables.
Abstract
NFPA 70, National Electrical Code® (NEC) permits
communications and optical fiber cable substitutions based on a
fire performance hierarchy. The principle is that cable types
higher in the hierarchy are permitted to substitute for cable types
that are lower in the hierarchy. The Canadian Electrical Code
(CEC) and the National Building Code of Canada (NBCC) which
together specify communications cabling requirements in
buildings in Canada also have a similar hierarchy.
Figure 1. Communications Cable Fire Performance
Hierarchy
This paper reviews the fire tests used for listing communications
cables and optical fiber cables, and the rationale for the cable
substitution hierarchies. New test data are presented which show
that FT6 rated cables have superior results as compared to the
requirements of the FT4 test, thereby supporting the current
hierarchy in the Canadian codes.
Keywords: Wire; cable; symposium; fire, smoke; fire test;
hierarchy; NFPA; NFPA 70; National Electrical Code; NEC;
Canadian Electrical Code; CEC; National Building Code of
Canada; NBCC; plenum ; riser; general-purpose; FT6; FT4;
2. NEC Requirements
1. Introduction
Fire performance requirements for cables have been in the National
Electrical Code since the first edition in 1897; it had a requirement
that riser cables not spread fire from floor to floor. However,
without a requirement for listing, it is difficult to enforce such a
requirement. Listed products are certified by a recognized testing
laboratory as meeting a standard. Enforcing authorities, typically
electrical inspectors, rely on listings to assure that a product meets
code requirements.
Figure 1 illustrates the communications cable fire performance
hierarchy in the 2017 NEC.
Plenum cables are on top of the hierarchy; they are permitted to
substitute for riser, general-purpose and limited-use cables. Next
down in the hierarchy are riser cables, which are permitted to
substitute for general-purpose and limited-use cables. Next down
are general-purpose cables, which are permitted to substitute for
limited-use cables. Limited-use cables are on the bottom of the
hierarchy. The principle is that cable types higher in the hierarchy
are permitted to substitute for cable types that are lower in the
hierarchy.
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Plenum cables were the first communications cables to be listed as
meeting fire performance requirements.
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cable, not in conduit, outperformed the conventional cable, in
conduit, the candidate plenum cable earned a listing as a plenum
cable.
2.1 Plenum Cable Listing
In an office building, the space between a hung ceiling and the floor
above is a very convenient place for installing communications
cables. Since this space is commonly used as a return air plenum,
there are fire protection concerns that must be addressed. Moving air
can drive fire spread and circulate smoke through the building.
The first listings of plenum cables were in 1978. Since these listings
only addressed the fire properties of communications cables,
Underwriters Labs referred to them as “classifications”. UL uses the
term “Listed” to indicate a comprehensive safety certification.
Figure 2. Cables Installed in a Plenum
The fire protection requirements for listing plenum cables are in
NFPA 90A-2015, Standard for the Installation of AirConditioning and Ventilating Systems6. It requires that cables
shall be listed as having a maximum peak optical density of 0.50
or less, an average optical density of 0.15 or less, and a maximum
flame spread distance of 1.5 m (5 ft) or less when tested in
accordance with NFPA 262, Standard Method of Test for Flame
Travel and Smoke of Wires and Cables for Use in Air-Handling
Spaces. UL 910 has been withdrawn and replaced by NFPA 262.
Figure 3. NFPA 262 Test
The National Electrical Code has a long-standing requirement that
power cables installed in plenums must be in metal conduit or
metallic-sheathed cables be used1. However, there were no
requirements for communications cables installed in plenums until
the 1975 NEC edition.
The 1975 NEC added a new requirement that communications
cables installed in plenums be installed just like power cables, but
also provided an exception for cables with “inherent fire-resistant
and low-smoke producing characteristics2”.
The 1975 Code did not provide any guidance as to what a cable with
“inherent fire-resistant and low-smoke producing characteristics”
was. In order to establish requirements for these yet-to-be named
plenum cables, a fire test had to be specified for measuring the flame
spread and smoke producing characteristics of cables and then
pass/fail requirements had to be established. The development of a
test was reported at the 1976 IWCS in a joint paper3 by Bell Labs
and Underwriters Labs. The test became UL 910, UL Standard for
Safety Test for Flame-Propagation and Smoke-Density Values for
electrical and Optical-Fiber Cables Used in Spaces Transporting
Environment Air. Use of this test for measuring the flame spread
and smoke production of cables installed in a plenum was validated
by a series of large-scale fire tests4.
Since the National Electrical Code permits cables installed in
metal conduit to be a suitable installation method for installations
in plenums, risers and general-purpose spaces, and the listing
requirements for plenum cables are based upon their equivalency
to cables installed in metal conduit, it should be clear that plenum
cables should be permitted to be installed wherever cables in
metal conduit are permitted to be installed. That clearly puts
plenum cables on top of the cable substitution hierarchy.
2.2 Riser Cable Listing
In 1980, a joint project between Bell Laboratories and Underwriters
Laboratories developed a fire test for listing riser cables7, 8. The riser
cable fire test, UL 1666, Standard for Test for Flame Propagation
Height of Electrical and Optical-Fiber Cables Installed Vertically
in Shafts, simulates a cable installation in a building riser shaft. The
cables are ignited by a very large (495,000 Btu/hr) burner. To pass,
cables must not propagate flame to the top of the 12-foot-high
compartment during a 30-minute test.
Establishing a test was the first step in establishing a listing process
for plenum cables. The next step was choosing the pass/fail criteria.
Since it had been established that cables installed in metal conduit
are an acceptable and code-compliant way of installing cables in a
plenum, the listing concept was that plenum cable had to perform as
well as conventional (non-plenum) cable in metal conduit. Extensive
testing of cables in conduits was reported by Underwriters Labs,
Bell Labs and E.I. du Pont de Nemours5. Prior to the establishment
of pass/fail criteria, a manufacturer seeking the listing of a “plenum”
cable had to submit the cable in two versions, a conventional cable
and a candidate plenum cable. The flame spread and smoke
production of the conventional cable, in conduit, was compared to
the flame spread and smoke production of the candidate plenum
cable, not in conduit, in the UL 910 test. If the candidate plenum
International Wire & Cable Symposium
The 1984 NEC required that riser communications cables be listed.
It stated, “Communications wires and cables, both metallic
conductor and optical fiber types, in a vertical run in a shaft be listed
as having fire-resistance characteristics capable of preventing the
carrying of fire from floor to floor.”
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The 1984 NEC did not have a provision explicitly permitting
plenum cables to substitute for riser cables. Fire performance
requirements for top two cables in the hierarchy were established,
but there was no hierarchy yet.
The Fine Print Note, now called an Informational Note, for plenum
cables in the NEC correlates with the mandatory requirements for
plenum cable testing in NFPA 90A, Standard for the Installation
of Air-Conditioning and Ventilating Systems6.
The 1987 code referred to the Vertical Tray Fire Test in UL 1581
testing Type CM cables, and the VW-1 requirements in UL 1581
for testing Type CMX cables. The vertical tray test is often
referred to as the IEEE 383 fire test.
Figure 5. Vertical Tray Flame Test
Figure 4. UL 1666 Test
Figure 6. VW-1 Flame Test
2.3 Listing of all Communications Cables
The 1987 NEC required that “Communications wires and cables in
a building shall be listed as being suitable for the purpose9”, thereby
expanding the listing requirements beyond “classification, to a
complete safety listing. Listing plenum cables “as having adequate
fire-resistant and low-smoke producing characteristics” and riser
cables “as having fire-resistant characteristics capable as preventing
the carrying of fire from floor to floor” was no longer sufficient; the
cables now had to also “be listed as being suitable for the purpose”.
The 1987 Code also required that plenum and riser cables be
marked CMP and CMR respectively.
It introduced two new cable types10, Type CM general-purpose
communications cables and Type CMX limited-use communications
cables. With four different types of communications cables, each
with a different level or fire resistance, it was necessary to clarify
what fire performance was required of each cable type, and to do so
without violating the NEC prohibition on mandatory references to
other standards.
The cable fire performance fire hierarchy has its origin in the
1987 NEC which explicitly permitted certain cable substitutions.
In the section on vertical runs it required riser cable (Type CMR)
and states “Type CMP wires and cables listed for use in ducts,
plenums, or other air-handling spaces in accordance with Section
800-3(b)(3) shall be permitted to be used to meet the requirements
of this section13”. In the section on (general) wiring in buildings it
states “Type CMR wires and cables listed for use in vertical runs
in accordance with Section 800-3(b)(2) and Type CMP wires and
cables listed for use in ducts, plenums, or other air-handling
spaces in accordance with Section 800-3(b)(3) shall be permitted
to be used to meet the requirements of this section14.”
The 1984 Code referred users to the test requirements for plenum
cables with a Fine Print Note that stated “One method of defining
low-smoke producing materials is by establishing an acceptable
value of the smoke produced per the UL 910 test to a maximum
peak optical density of 0.5 and a maximum average optical density
of 0.15. Similarly, fire-resistant cables may be defined as having a
maximum allowable flame travel distance of 5 feet (1.53 m) in the
UL 910 test11.”
An exception to the use of Type CM for general wiring in
buildings covered the use of Type CMX cables14.
“Exception No. 3: Listed Type CMX communication wires and
cables that are less than 0.25 inch (6.35 mm) in diameter and
installed in one- and two-family or multifamily dwellings.”
The Fine Print Note in the 1987 Code stated: “One method of
defining low-smoke producing wires and cables is by establishing
an acceptable value of the smoke produced per the NFPA 262-1985
test to a maximum peak optical density of 0.5 and a maximum
average optical density of 0.15. Similarly, fire-resistant wires and
cables may be defined as having a maximum allowable flame travel
distance of 5 feet (1.53 m) in the NFPA 262-1985 test12.”
International Wire & Cable Symposium
Until the development of the 1987 NEC, only the two fire
scenarios of greatest concern, cables in air handling spaces and in
risers, were addressed. There were no requirements for cables run
in other building spaces. Proposal 16-15515 for the 1987 NEC
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Figure 7. Vertical Tray Flame Tests
stated, “It is permissible under the present code to use
polyethylene-jacketed outside plant cable anywhere except the
plenum or riser shaft, for example in hung ceilings not used for air
handling.” NEC Panel 16 agreed to require that communications
cables used in buildings be listed, but not without first debating
which test should be used for general-purpose cable, the IEEE383 test or the VW-1 test. The Panel choice of the IEEE 383 test
was opposed by comments16 that stated the IEEE 383 test was for
“extremely high risk application involving nuclear power
generating plant” and recommended VW-1 which was already in
use for “low voltage computer cables”. The Panel rejected the
comment with the statement “The Panel believes that the
requirements of UL VW-1 are not severe enough to meet the
Panel’s intent.”
An explicit cable substitution table and a cable substitution figure
were introduced in the 1990 NEC.
2.4 Optical Fiber Cables
As per NBCC requirements, buildings required to be of
noncombustible construction must have communications cables
rated to FT6 in plenum spaces and FT4 elsewhere in the building.
Buildings permitted to be of combustible construction require
communications cables with an FT4 rating in the plenum and FT1
elsewhere in the building. Note that the Province of Ontario requires
that FT6 rated communications cables must be used in plenums of
all buildings regardless of construction type (combustible or
noncombustible construction).
Article 770, Optical Fiber Cables, was introduced into the 1984
edition of the NEC. The fire performance requirements for optical
fiber cables installed in plenums and risers were identical to the
requirements for communications cables. The 1987 edition has three
levels of fire performance, plenum, riser and general-purpose. Since
there are nonconductive (all dielectric) optical fiber cables and
conductive optical fiber cables which have a non-current-carrying
metallic member, and three levels of fire performance, there are
three types of nonconductive optical fiber cables, Types OFNP,
OFNR and OFN, and three types of conductive optical fiber cables,
Types OFCP, OFCR and OFC. The fire performance hierarchy is
the same as the hierarchy for communications cables.
The CEC allows the following substitutions to be used as per
footnote 21 in Table 19:
a) Communications cables, under-carpet communications
(CMUC) cables, and cross-connect wires (cables) marked CMP,
CMR, CMG, CM, CMX, CMH, FT6, FT4, and FT4/IEEE 1202
have been found to meet the standard criteria for FT1.
3. Canadian Electrical Code
Requirements
The Canadian Electrical Code (CEC) works in tandem with the
National Building Code of Canada (NBCC) to define what fire
rating is required for communications cables in different spaces in a
building and in fact, the requirements differ depending on whether
the building is of combustible or non-combustible construction. The
CEC also uses different designations than the NEC for fire test
ratings.
(b) Communications cables, under-carpet communications
(CMUC) cables, and cross-connect wires (cables) marked CMP,
CMR, CMG, and FT6 have been found to meet the standard
criteria for FT4 and FT4/IEEE 1202.
(c) Communications cables, under-carpet communications
(CMUC) cables, and cross-connect wires (cables) marked CMP
have been found to meet the standard criteria for FT6.
The CEC and NBCC use three different fire test (FT) ratings to
classify communications cables. The FT6 test is the NFPA 262 test
which is a horizontal test. The FT4 or FT4/IEEE 1202 test is a
vertical test17, and the FT1 test is also a vertical test, but less severe
than the FT4 test. The FT1 test is similar to the VW-1 test. Figure 7
shows the significant differences between the US vertical flame test
(on the left of Figure 7) and Canadian FT4 (on the right of Figure 7)
vertical flame tests. The FT4 test is more severe because the burner
is tilted up 20o, and the maximum char length is less, only 150 cm in
the FT4 test versus 244 cm in the US test.
4. Fire Tests
Recent research has been done to support the substitution of FT6
rated cables (Types CMP, OFNP & OFCP) where FT4 rated cables
(Types CMG, OFNG & OFCG) are required. Three different FT6
(Plenum) rated cable types were tested, 1) Cat 6A UTP, 2) RG-11
Coax, and 3) a Composite Communications/ Optical Fiber. All were
subjected to the FT4 test at UL Laboratories18.
Figures 8, 9 and 10, show that all three cables passed with a very
wide margin. The char on the Cat 6A UTP cable was 53 cm, on the
RG-11 Coax char was 51 cm and the char on the Composite Optical
Fiber Optic cable was 65 cm. The maximum char length allowed for
FT4 is 150 cm.
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Figure 8. CSA FT 4 Vertical Tray Flame Test Results, CAT
6A, Type CMP Cable
samples provided by Belden. We thank UL for carrying out the fire
tests professionally and quickly.
Dr. Kaufman, who is a consultant to CCCA, thanks CCCA for their
support.
7. References
[1] NFPA 70-2017, National Electrical Code, Section 300.22(C).
[2] NFPA 70-1975, National Electrical Code, Section 800-3(d).
[3] J. R. Beyreis, J. W. Skjordahl, S. Kaufman, M. M. Yocum, "A
Test Method for Measuring and Classifying the Flame Spreading
and Smoke Generating Characteristics of Communications
Cable," Proceedings of the 25th International Wire and Cable
Symposium, 1976, pp. 291-295.
[4] S. Kaufman, M. M. Yocum, “The Behaviour of Fire-Resistant
Communications Cables in Large-Scale Fire Tests,” Plastics in
Telecommunications 11, p. 8-1. Also published in Plastics and
Rubber: Materials and Applications, 4, No. 4, Nov. 1979, pp.
149-155.
Figure 9. CSA FT 4 Vertical Tray Flame Test Results, RG11 Coaxial Cable, Type CMP Cable
[5] S. Kaufman, L. J. Przybyla, E. J. Coffey, M. M. Yocum, J. C.
Reed, D. B. Allen, “Low Smoke and Flame Spread Cables,”
Proceedings of 28th International Wire and Cable Symposium,
1979, pp. 281-291. Also published in Journal of Fire and
Flammability, 12, 1981, pp. 177-199.
[6] NFPA 90A-2015, Standard for the Installation of AirConditioning and Ventilating Systems, section 4.3.4.4.
[7] S. Kaufman, J. L. Williams, E. E. Smith, L. J. Przybyla,
"Large Scale Fire Tests of Building Riser Cables," Proceedings of
the Thirty-First International Wire and Cable Symposium, pp.
411-416 and Proceedings of the International Conference on Fire
Safety, pp. 105-117, Journal of Fire Sciences, I, January/February
1983, pp. 54-65.
Figure 10. CSA FT 4 Vertical Tray Flame Test Results,
Composite Communications/ Optical Fiber Cable, Type
CMP/OFCP
[8] L. J. Przybyla, T. J. Guida, J. L. Williams, S. Kaufman, "Fire
Testing of Riser Cables," Proceedings of the 33rd International
Wire and Cable Symposium, 1984, pp. 5-13, Proceedings of the
International Conference on Fire Safety, 10, 1985, pp. 120-133,
Journal of Fire Sciences, 3, 1985, pp. 9-25.
[9] NFPA 70-1987, National Electrical Code, Section 800-4.
[10] NFPA 70-1987, National Electrical Code, Section 800-3(b).
[11] NFPA 70-1984, National Electrical Code, Section 8003(b)(3).
[12] NFPA 70-1987, National Electrical Code, Section 8003(b)(3).
[13] NFPA 70-1987, National Electrical Code, Section 8003(b)(2).
5. Conclusions
[14] NFPA 70-1987, National Electrical Code, Section 8003(b)(1).
The fire test data support the long-established fire performance
hierarchy in the NEC and the CEC.
[15] NEC-TCRA-1986, Proposal 16-155
6. Acknowledgments
[16] NEC-TCDA-1986, Comment 16-20
The fire tests were conducted by Underwriters Laboratories for the
Communications Cable & Connectivity Association (CCCA) on test
[17] Provisional Specification- Tests to Determine Fire
Retardancy and Acid Gas Evolution of Insulated Power and
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Control Cables (No. L-891SM-77). Ontario Hydro, Canada
(1977).
focus on wire and cable products and their fire safety and
performance since 2001.
[18] UL 1685 FT4.IEEE 1202,Vertical-Tray and FlamePropagation and Smoke-Release Tet for Electrical and Opticalfiber Cables,2015
Fred is a member of several fire safety related ASTM
Subcommittees, and was a member of the Canadian National
Research Council’s Task Group on Plenum Cables. Fred is the
Chair of the Wire and Cable Section of the Plastics Industry
Association (previously the Society of the Plastics Industry-SPI)
Fluoropolymer Division as well as a US TAG member on IEC TC
89 and a member of the Canadian IEC TC 111 Mirror Committee.
He is also a member of the IEEE (Institute of Electrical and
Electronic Engineers) 802.3bt Task Force which is developing the
most current PoE (Power over Ethernet) standard as well as the
TIA (Telecommunications Industry Association) 42.7 Copper
Communications Committee. Additionally, he is a member of
IEEE 45.8, practice for selection, application and installation of
electrical power, signal, control, data and specialty marine cable
systems, shipboard.
8. Authors
Fred is also the American Chemistry Council (ACC) Principal
Representative on the NFPA National Electrical Code (NEC)
Code Making Panel 16 (CMP 16).
Fred holds a Bachelor of Mechanical Engineering degree from
Concordia University (Montréal) as well as a Graduate Diploma
in Business Management from McGill University (Montréal).
*Effective July 1, 2015 the chemical businesses including the
Fluorine businesses of DuPont were spun off to become the
Chemours Company. At that time Fred became employed by
Chemours.
Fred Dawson
The Chemours Canada Company
2233 Argentia Road, Suite 402
Mississauga, Ontario
L5N 2X7
Since 1992 Fred has had responsibility for Regulatory Affairs
within DuPont Canada’s Fluorine Products business (now
operating as Chemours*), and expanded his role to include
Regulatory Affairs for DuPont’s Fluoropolymer Solutions
Business in the U.S. in 2005. Fred has over 40 years’ experience
in sales and marketing in DuPont Canada’s Electronics and
Fluoroproducts businesses. He is currently the Regulatory Affairs
Manager for the Fluoropolymer business and has had a primary
International Wire & Cable Symposium
Gerald Lee Dorna
Belden
5200 U. S. Highway 27 South
Richmond, IN., 47374
Gerald Lee Dorna received is BSEE degree from Memphis State
University in 1973. He has been employed by Belden for over 44
years and is currently the Technical Relations Manager. He has
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most of his professional career at Bell Labs/AT&T/Lucent
Technologies in Norcross, GA.
been involved with the National Electrical Code (NEC) since
1989 and became a member of Code Making Panel 16 (CMP-16)
in 1995. Gerald currently is a member on UL’s Standard
Technical Panel (STP) 13, 62, 83, 758 and 814. He is a member
of CSA Technical Sub-Committee on Control, Instrument,
Communication, and Marine Cables C231 (ICWC05). He is also
a member of ASTM, CANENA, ICEA, IEEE, and NEMA and
serves on different committees within these organizations.
He was a frequent contributor to the IWCS since he presented his
first paper at the 21st IWCS in1972 and won the best speaker
award. His involvement with the National Electrical Code started
when the 1975 NEC introduced rigorous installation requirements
for cable installed in plenums. That change required a test for
certifying the fire performance of plenum cables “as having
adequate
fire-resistant
and
low
smoke-producing
characteristics”. Stan and his coworkers at Bell Labs and
Underwriters Labs presented a paper on the development of the
plenum cable fire test, initially UL 910 an now NFPA 262, at the
25th IWCS in 1976.
At the 35th IWCS in 1982, Stan and his coworkers at Bell Labs,
Underwriters Labs and from Ohio State University presented a
paper on the development of the riser cable fire test, UL 1666. UL
1666 is the test used for listing of riser cables as “having fireresistant characteristics capable of preventing the carrying of fire
from floor to floor”.
Stan remained active in the codes work after retiring from Lucent
Technologies. He currently serves on four National Fire
Protection Association Technical committees:
NEC Panel 16: alternate representative to Gerald Dorna
representing ICEA
NEC Panel 12: representing the PLASTICS Industry Association,
(formerly SPI)
Dr. Stanley Kaufman
Technical Committee on Electronic Computer Systems (NFPA
75): representing PLASTICS
CableSafe, Inc.
P.O. Box 50082
Technical Committee on Telecommunications (NFPA 76):
representing PLASTICS
Atlanta, Georgia 311150-0082
Stan Kaufman has a B.S. in Physics from City College of New
York and a Ph.D. in Chemistry from Brown University. He spent
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