Codes, especially building and fire codes, regulate the fire
properties that must be exhibited by interior finish materials that are
used in regulated building environments.
Interior finish, as regulated by codes in the U.S., can be subdivided
into four types of materials or products: interior wall finish,
interior ceiling finish, interior floor finish and trim. The International Building Code®1 defines as follows:
Interior floor finish: the exposed floor surfaces of buildings
including coverings applied over a finished floor or stair, including
Interior wall and ceiling finish: the exposed interior surfaces of
buildings, including but not limited to: fixed or movable walls and
partitions; toilet room privacy partitions; columns; ceilings; and
interior wainscoting, paneling or other finish applied structurally or
for decoration, acoustical correction, surface insulation, structural
fire resistance or similar purposes, but not including trim.
Trim: picture molds, chair rails, baseboards, handrails, door and
window frames, and similar decorative or protective materials used in
Not much has changed in terms of the basic interior finish
requirements for fire performance in the U.S, for many years. The
requirements are as follows:
Interior wall and ceiling finish materials (and interior trim) are tested using the Steiner tunnel test, ASTM E 84.2 The pass/fail criteria used by the codes for this test are:
Class A: Flame spread index: ≤ 25 – Smoke developed index: ≤ 450
Class B: Flame spread index: > 25 & ≤ 75 – Smoke developed index: ≤ 450
Class C: Flame spread index: > 75 & ≤ 200 – Smoke developed index: ≤ 450
Interior floor finish materials are tested using the flooring radiant panel test,
ASTM E 6483 or NFPA 2534 (which are equivalent). The pass/fail criteria used by the codes for this test are:
Class I: Critical radiant flux: ≥ 0.45 W/cm2
Class II: Critical radiant flux: ≥ 0.22 W/cm2 & < 0 .45 W/cm2
Once these basic concepts were set up, exceptions and clarifications
have gradually been added, because some types of materials are
considered to have unusual fire performance characteristics. Thus, for
example, exceptions were put in place for trim because there was very
little of it, and special requirements were put in place for foam
plastic insulation because testing in accordance with ASTM E 84 gave
misleading results. Also, very thin materials (< 0.9 mm thick) and
structural wood were exempt from testing.
In the 1990s, room-corner tests were allowed as alternate tests to
the Steiner tunnel test. The key room-corner test is NFPA 286,5
which is now applicable to all interior wall and ceiling finish
materials. Just like ASTM E 84 and ASTM E 648 or NFPA 253, the NFPA 286
test method itself does not contain approval requirements. The pass/fail
criteria U.S. codes apply for regulating materials that are tested
using NFPA 286 are: no flashover, peak heat release rate of 800 kW, no
flame spread to the corners of the ceiling, and a total smoke release
not exceeding 1,000 m2. If a material meets the above NFPA
286 criteria, it is allowed anywhere that a Class A material (in
accordance with ASTM E 84) is required. No definitive studies have shown
equivalence between the pass/fail criteria for both tests, but
consensus exists that materials which release little heat and smoke, and
don't go to flashover in the room-corner test are likely to exhibit
reasonable fire performance.
So, are trends flat? In fact, no, since a lot of improvements are
underway, principally in terms of tightening loopholes. The three key
examples of activity follow.
Specific requirements associated for certain materials or products
Textile and expanded vinyl wall and ceiling coverings have been shown
to give potentially misleading results (because the samples are very
thin). Therefore, if they are tested only with ASTM E 84, they normally
require sprinkler protection. Moreover, an alternate room-corner test,
NFPA 265,6 was designed for textile wall coverings, but
cannot be used for ceiling coverings (because the flame does not reach
the room ceiling). The screening test option (Method A) in NFPA 265 is
also being eliminated.
Foam plastic materials must be tested using NFPA 286 (even when they
have a textile or vinyl covering) or they must be covered with a thermal
barrier. The thermal barrier itself needs to protect the foam plastic
for 15 minutes and cannot contribute to the fire.
Trim is allowed to exhibit poorer fire performance than interior
finish if it covers less than 10 percent of the wall or ceiling. Foam
plastic trim also has thickness and density limitations.
Interior floor-wall base, up to a width of 152 mm, is tested in
accordance with ASTM E 648 instead of using ASTM E 84 or NFPA 286.
Many surfaces, such as movable walls and partitions, paneling, wall
pads and crash pads, are being considered interior finish materials as a
whole and not decorations, nor is the top layer considered just a
stand-alone wall covering.
Steiner tunnel mounting practices
The standards that describe Steiner tunnel testing have tended to
leave broad discretion to the labs (and to the test sponsors) in how to
prepare test specimens and mount them during the test. This has resulted
in some excesses, including testing of individual components instead of
systems (when the fire performance of a system can be very different
from the combined fire performance of the individual materials, such
that each layer can meet requirements while the system does not),
allowing materials to melt and continue burning on the floor while
reporting ceiling flame spread (which of course would not happen of the
material is on the floor), placing materials in contact with heat sinks
(such as chicken wire), filling materials with water to minimize visible
flame spread, testing materials at less than full width and many
others. Committee ASTM E05, on Fire Standards, has now developed four
standard practices, to make testing of some materials fully
standardized. They are ASTM E 22317 (pipe and duct insulation materials and systems), E 24048 (textile, paper or vinyl wall or ceiling coverings), E 25739 (site-fabricated stretch systems) and E 257910
(wood products). Reference to all of these practices is being gradually
added to ASTM E 84, while relying less on the appendix guidance
sections. Work is underway on several other practices, including ones
intended to apply to reflective insulation systems and vapor barriers.
Materials in plenums
The basic requirements for materials in plenums are that the material
exhibit Steiner tunnel pass/fail criteria of a flame spread index not
greater than 25 and a smoke developed index not greater than 50.
However, special criteria need to be in place for some materials,
including foam plastic insulation, which cannot be tested properly in
the Steiner tunnel and require added criteria.
Interior finish materials are key components of the fire safety of a
building, and therefore, the more is known about the materials used, the
more efficiently and appropriately they can be tested, and regulated,
for better fire safety of the building's users.
International Building Code®, International Code Council, Washington, DC., 2006.
ASTM E 84: Standard Test Method for Surface Burning Characteristics of
Building Materials, ASTM International, West Conshocken, PA, 2007.
ASTM E 648: Standard Test Method for Critical Radiant Flux of
Floor-Covering Systems Using a Radiant Heat Energy Source, ASTM
International, West Conshohocken, PA, 2006.
NFPA 253: Standard Method of Test for Critical Radiant Flux of Floor
Covering Systems Using a Radiant Heat Energy Source, National Fire
Protection Association, Quincy, MA, 2006.
NFPA 286: Standard Methods of Fire Tests for Evaluating Contribution
of Wall and Ceiling Interior Finish to Room Fire Growth, National Fire
Protection Association, Quincy, MA, 2006.
NFPA 265: Standard Methods of Fire Tests for Evaluating Room Fire
Growth Contribution of Textile Coverings on Full Height Panels and
Walls, National Fire Protection Association, Quincy, MA, 2007.
ASTM E 2231: Standard Practice for Specimen Preparation and Mounting
of Pipe and Duct Insulation Materials to Assess Surface Burning
Characteristics , ASTM International, West Conshocken, PA, 2007.
ASTM E 2404: Standard Practice for Specimen Preparation and Mounting
of Textile, Paper or Vinyl Wall or Ceiling Coverings to Assess Surface
Burning Characteristics , ASTM International, West Conshocken, PA, 2007.
ASTM E 2573: Standard Practice for Specimen Preparation and Mounting
of Site-Fabricated Stretch Systems to Assess Surface Burning
Characteristics , ASTM International, West Conshocken, PA, 2007
ASTM E 2579: Standard Practice for Specimen Preparation and Mounting
of Wood Products to Assess Surface Burning Characteristics , ASTM
International, West Conshocken, PA, 2007.
Marcelo M. Hirschler is with GBH International.
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