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Flammability Test method for carpet
This work established that the performance measured in and regulated by the Flooring Radiant Panel is complementary to that measured in the Cone. While the Early Fire Hazard Test and Cone provide information to assess the fire performance of materials for upward flame spread, the Flooring Radiant Panel (and LIFT) gives a suitable complementary measure (critical heat flux) of flame spread on horizontal surfaces. While The Flooring Radiant Panel does not currently measure smoke generation nor is it suitable for determining upward flame spread for floor coverings used on stairs or ramps, the Cone Calorimeter can provide the additional data needed for these predictions.
VERTICAL AND HORIZONTAL FLAME SPREAD:
The Early Fire Hazard Test (EFH) is a medium-scale test that is currently called up by the Building Code of Australia (BCA) to control the use of building linings (floors, walls and ceilings). We include a brief description of the test, as it might not be familiar to those outside Australia. A specimen of floor covering 600 x 450 mm is clamped in a vertical holder which faces a gas-fired radiant panel. The specimen holder is moved towards the radiant panel in a series of programmed steps over a period of 20 minutes, or until the specimen ignites, at which time the movement is stopped. Ignition is promoted by a gas pilot flame mounted 15 mm clear of the centre of the exposed face of the specimen, triggering the decomposition products rather than the specimen itself. If ignition occurs the radiation and smoke production of the specimen are monitored for 2 minutes (or more in certain cases) (Dowling and Blackmore, 1998).
EFH is a medium scale test for predicting flame spread on vertical surfaces. Under the current Australian Standard, data obtained can be used to derive indices that are generally suitable for application in deemed-to-satisfy regulations. However, the data is not suitable for use in fire engineering calculations, and the test method itself is not without problems. Its applicability for predicting performance of horizontal surfaces is not appropriate. In addition, certain materials, especially those that melt and drop away from the backing when exposed to heat, give low indices because of the lack of burning material at the point of most intense radiation. This does not reflect their behaviour in a horizontal orientation, where molten material will stay in place until it is burnt.
Other materials that have a high critical radiant flux and thus do not ignite easily can produce high flame spread indices in the EFH because these indices are calculated from measurements taken from the time of ignition, regardless of the incident radiant flux at which ignition occurs.
The Early Fire Hazard test was originally developed to overcome difficulties experienced in the use of BS476.7, Surface Spread of Flame Test, for vertical flame spread. BS476.7 measures lateral flame spread on a specimen exposed to a decreasing radiant field. John Ferris of the Commonwealth Experimental Building Station, where the test was developed, was aware that vertical flame spread was different from horizontal flame spread, and that BS 476.7 did not take into account the heat release rate that was necessary to predict vertical spread. He developed the EFH to overcome these difficulties. In the EFH the radiation levels as the panel approaches the burner simulate the radiation levels measured by Ferris in the ASTM or ISO room corner test. EFH became an Australian Standard and measurements in the form of indices for spread of flame and smoke developed were subsequently invoked in regulations to control the use, not only of vertical linings as originally intended but also of horizontal linings.
Figure 1 shows a comparison between Flame Spread as measured in accordance with BS 476:1953
and Time Interval (defined as the time from ignition to that for flames to reach a height corresponding to a 9ft high ceiling, which is related to the Flame Spread Index in the current EFH standard) measured in the Vertical-spread-of-flame Apparatus (as EFH was then known). The comparison shows that there is little or no correlation between the two values. This early observation, taken from a paper written by Ferris in 1955, showed clearly that the Vertical-spread-of-flame Apparatus (as EFH was then known) is suitable for measuring upward flame spread for wall linings, but it cannot characterise horizontal flame spread. Unfortunately the detailed work of Ferris was subsequently overlooked when the EFH was adopted for control of flame spread on horizontal surfaces.
2019-03-15 17:10
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