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|Trends in Interior Finish Requirements|
Issue 16: Trends in Interior Finish Requirements
By Marcelo M. Hirschler, Ph.D.
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:
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:
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
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.
Marcelo M. Hirschler is with GBH International.
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