Flammability Testing
Pill Test: Since April 1971, Federal regulations have required that all carpet sold in the United States pass the Pill Test (1) +. The test will screen out carpet easily ignited by a small incendiary source; if measures the response of carpet exposed to a timed burning tablet in the absence of an imposed external radiation field. Carpet which passed the Pill Test will not spread flame during a Stage 1 fire. This was further demonstrated in a series of room tests conducted by the National Bureau of Standards (2). This series of experiments reconfirmed the conclusion that: "Carpet systems, used in rooms, will not normally spread fire provided they meet the requirements of the DOC ff 1-70 (Pill Test).
Tunnel Test: The ASTM E-84 "Tunnel Test" was originally developed to evaluate the fire hazards of wall and ceiling materials. When this method is used for carpet, a con- ditioned sample is mounted upside down on the "roof" of the tunnel. As a consequence this method does not provide meaningful real-life information for judging the relative fire hazards of carpet. There is agreement with the technical fire protection community that the tunnel test does not yield data which predict the probable performance of flooring systems in actual building fires.
Chambers Test: The Chamber Test (UL-992) was developed to evaluate fire behavior of flooring systems. The test is a variation of the Tunnel Test in that the sample is exposed to high intensity burner in a tunnel. The specimen is placed on the floor, enabling floor covering assemblies, including carpet with separate underlayment, to be evaluated in this apparatus. In this test the forced draft, suppling air to the flame, sweeps the carpet in the opposite direction to that observed on the floor in full-scale corridor fires.
This test has technical shortcomings (3, ll) in that:
a. The Chamber Test generates an index which has an undetermined relevance to fire hazard.
b. The degree of reproducibility of data resulting from the Chamber Test is not established.
c. Indices produced by tests conducted in the Chamber tend to divide materials into two polarized groups; therefore, a continuous classification scale is not provided to categorize materials.
Flooring Radiant Panel Test: Since neither the existing Tunnel Test nor the Chamber Test adequately evaluates flooring materials; a new test was developed, called the Flooring Radiant Panel Test (10). This test is designed to simulate a likely set of conditions which may lead to fire spread in a carpet. system. The Flooring Radiant Panel concept evolved from information obtained from the full scale corridor fire test programs. The full scale tests showed that the level of energy radiating onto carpet significantly affected whether or not progressive flaming occurred. This test method determines a critical radiant flux, measured in watts per square cent- imeter (watts/cm). Critical radiant flux is the lowest level of radiant energey necessary for a fire to continue to burn and spread.
The Flooring Radiant Panel Test is different from most other fire test methods in that it measures an actual property of the carpet system and is not based on an arbitrary scale. The test yields data correlated to the relative performance of materials in actual installations. In this test, the floor covering system is installed on the "floor" of the test chamber similar to a "real world" situation. The test can accomodate floor system assemblies, such as carpet with a separate underlayment.
The Flooring Radiant Panel apparatus involves a horizontally mounted floor covering test sample which receives radiant energy from a gas-air fueled radiant panel mounted above one end of the sample and inclined at an angle of 30 degrees. The sample and radiant panel are located within a test chamber. Air is allowed to flow in the bottom of the test chamber and exits via a stack located at the top of the chamber at the opposite end from the radiant panel.
The radiant panel generates a radiant flux profile along the length of the sample ranging from maximum of 1.1 watts/cm, immediately under the panel to approximately 0.1 watts/cm at the end of the test sample remote from the panel. A gas fired pilot burner is used to initiate the ignition on the floor covering sample immediately below the radiant panel and the test is continued until the flooring system ceases to burn. The distance the flooring system burns to extinguishment is converted to watts per square centimeter from a calibration graph and is reported as critical radiant flux.
Critical Radiant Flux: The result of the test is reported as the critical radiant flux (watts/cm). This is the minimum radiant energy a fire needs to sustain flame propagation in the flooring system. In this test, the lower the number, the greater is the tendency of the system to spread flame. Conversely, the higher the number, the more resistant is the material to flame propagation. This number is the average of the least three replicate burns. The test apparatus is capable of accommodation materials which have critical radiant flux values ranging from approximately 1.1 to 0.1 watts/cm. To relate these values to the critical radiant flux value of a traditionally used material, note that oak flooring has a critical radiant flux value of approximately 0.35 to 0.40 watts/cm. Carpet may have values from less than 0.1 to greater than 1.1 watts/cm. Data from the test have been shown to be both reproducible and repeatable, based upon a round-robin test series conducted under the supervision of the National Burea of Standards, involving ten carpet systems and twelve laboratories.
WHY TEST?
Experience has shown there is no way to predict the performance of a carpet system without conducting a test. The resistance of carpet to the spread of flame is a function of:
a. The generic type of face yarns used.
b. The type of construction, including yarn texture.
c. The density of the pile, and
d. The presence of an underlayment, attached or separate.
Also the presence of a separate underlayment may significantly affect the performance of carpet compared to test conducted on the same carpet without underlayment (10). Therefore, carpet tested without an underlayment may not be acceptable if used with an underlayment. Emphasis should be give to conduction tests based upon the type of assembly contemplated for use.
Recommended Criteria: The minimum critical radiant flux limits (based upon the average of three replicate tests) being recommended (11, 12) are:
a. 0.45 watts/cm within corridors and exitways of hospitals and nursing homes.
b. 0.22 watts/cm within corridors and exitways of other occupancies except one and two-family dwellings.
These values should provide a level of safety for the carpeted corridor which is equal to or in excess of that now required in the NFPA 101 Life Safety Code (13).
These limits are based upon:
a. Comparison to performance of traditionally used materials
b. Performance of flooring systems under full scale corridor test, and
c. Evaluation of carpet systems which have been reported as significantly contributing to flame spread in actual fires.
The higher level of critical radiant flux of 0.45 watts/cm, recommended for health care facilities, is based on the assumption that nonambulatory occupants (patients) require a higher level of protection that do occupants who are mobile and are capable of rapid escape.
Sprinklered Buildings: The radiant flux limits suggested for regulating floor covering are based upon the possiblity of a Stage 2 and Stage 3 fire. In a building completely protected by an automatic sprinkler system, the completely protected by an automatic sprinkler system, the likelihood of a Stage 2 fire developing becomes remote. The need for regulation of floor coverings under these circumstances diminishes. Therefore the criteria suggested above could be reduced or eliminated in the case where automatic sprinkler protection is provided (12).
|
