Mason Knowles
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All building materials can burn and release heat and toxic gases, causing injury or death. All building materials react differently
in a fire situation. And while the history of testing interior finishes for fire characteristics goes back to the early part
of the 20th century, it took a series of disastrous fires in the 1940s for the public to raise concerns sufficient enough
to take action.
The infamous fires at the Coconut Grove nightclub in Boston, the Chicago LaSalle Street Hotel, and the Atlanta Winecoff Hotel
killed more than 670 people and prompted the public to demand a reliable test to determine the flame spread and smoke development
of a building's interior finish in a fire situation and to classify them for use in buildings.
ASTM E-84 (Steiner tunnel test)
The predominant test accepted was the Steiner tunnel test, developed by Albert Steiner of Underwriters Laboratories (UL) from
the early 1920s to the '40s. Steiner used red oak as a baseline material because of its common use as a flooring material.The Steiner tunnel is a furnace chamber 25 feet long that measures flame spread and smoke development. The test compares the
surface flame spread and smoke generated to that obtained from tests of mineral fiber cement board and select-grade red oak.
The test procedure was first published by UL in 1950 and became an American Society for Testing and Materials (ASTM) standard
in 1961. How well your material performed against the baseline determined the classification of your building product.
The test is conducted with the specimen in the ceiling position, with the surface to be evaluated exposed face down to the
ignition source. The furnace is calibrated when a 10-minute test of red oak decking will pass flame out of the end of the
tunnel in 5 minutes 30 seconds (plus or minus 15 seconds). Mineral fiber cement board forms the zero point for flame spread
and smoke-developed indices, while the red oak flooring flame spread is typically around 90 and smoke developed index is set
at 100.
Flame is reported numerically from 1 to 100. Smoke generated is reported numerically from 1 to 1,000. From the flame spread
and smoke ratings, the material or product is listed in three classes: Class I (or A), Class II (or B), or Class III (or C),
or unrated:
- Class I: Flame spread 0-25; Smoke developed 0-450
- Class II: Flame spread 26-75; Smoke developed 0-450
- Class III: Flame spread 76-200; Smoke developed 0-450
Foam plastics and FTC consent decree
For the next 20 years, the Steiner tunnel test became the predominant method of determining if an interior finish was an acceptable
risk for use in construction. In the late 1960s to early '70s, foam plastic was becoming a popular alternative insulation
in buildings. Many companies advertised the foam based on the Steiner tunnel test as non-burning, non-combustible, and self-extinguishing.
Most foam plastics could achieve Class I and Class II ratings on their products, but the flame ratings did not accurately
predict the relative safety of their use in construction. Thermoplastic foams, such as expanded polystyrene (EPS) and extruded
polystyrene (XPS), would melt during the test, generating misleading low flame-spread values. Thermoplastic materials, such
as polyurethane foam, could generate flame or flashover conditions if large surface areas became involved in a fire.
After a series of fires involving foam plastics, the Federal Trade Commission (FTC) stepped in and demanded the foam plastics
industry address the issue. In 1974 the FTC entered into a Consent Decree and Order with the foam plastics industry (as represented
by the Society of the Plastics Industry [SPI]) that prescribed specific marketing and sales practices of foam plastics. The
Consent Decree and Order stated that all parties selling or installing foam plastic:
- Cease and desist from using, publishing, or disseminating (or encouraging others to use, publish or disseminate) descriptive
terms, such as 'non-burning,' 'self extinguishing,' or 'non-combustible' in connection with cellular foam plastics products
unless they perform as described under actual fire conditions;
- Refrain from referencing numerical flame spread ratings in connection with cellular foam plastic products, based on small-scale
flammability tests without a detailed disclaimer noting that the ratings are not predictive of the hazards presented by these
products under actual fire conditions;
- Implement a notice and reporting program on the terms and conditions of, and compliance with, the order;
- Establish and fund a research program on the safe and effective use of cellular foam plastic products.
In the 1970s SPI, working in conjunction with downstream industry groups, such as the Urethane Foam Contractors Association
(UFCA), the polyurethanes division of SPI, and the polystyrene foam groups, conducted extensive large-scale tests on foam
plastics and various coverings. From this research new fire-performance tests were developed that more accurately demonstrated
the behavior of wall and ceiling assemblies under realistic fire situations. Specific thermal barrier materials were identified,
such as half-inch gypsum drywall and 1-inch-thick masonry/cement/plaster along with the development of specific room corner
fire tests that could determine what designs, materials, and/or assemblies could be acceptable in construction (such as UL
1715, Factory Mutual [FM] 4880, Uniform Building Code [UBC] 26-3, National Fire Protection Association [NFPA] 286, etc.).
The foam plastic industry established safe-use guidelines adopted by the various building codes that remain substantially
unchanged to this day.
MASON KNOWLES has more than 37 years of experience in the polyurethane industry as a contractor, material supplier/manufacturer, equipment
manufacturer, and trade association professional.
