- Author
-
Babrauskas, V.
|
Richardson, L.
- Title
- Determining Non-Combustibility Through Heat Release Rate Measurement.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
Forintek Canada Corp., Ottawa
- Book or Conf
- Interscience Communications Limited. Heat Release and Fire Hazard. 1st U. S. Symposium. Abstracts. December 1991,
San Diego, CA,
11-12 p.,
1991
- Keywords
-
heat release
|
fire hazard
|
heat release rate
|
noncombustion
|
tests
|
cone calorimeters
|
test methods
|
building codes
- Identifiers
- ISO 1182; ASTM E136
- Abstract
- Non-combustibility has typically been determined by procedures such as ISO 1182 and ASTM E136, and supplemented by additional building code provisions intended to pass some known-to-be safe materials which otherwise fail the standard test. These non-combustibility tests have been designed rather artitrarily, and their measurements do not correspond to any of the rational engineering variables used to describe fires. Thus, in ISO and in a number of individual countries the desire was expressed to progress on to a newer generation of test concepts for non-combustibility. For doing this, it became clear that demanding non-combustibility should be interpreted as a way of insisting on a low heat release rate (HRR). Thus, in the long term, the entire concept of non-combustibility could be appropriately discarded, just as "fireproof" is already deprecated. In the short term, however, it was considered appropriate to find a better measuring technique, while not yet demanding an immediate removal of the concept from regulatory documents. Thus in several laboratories as started to characterize non-combustibility by doing HRR tests and devising appropriate criteria for acceptance. The goal of this work is to classify materials into the same classes as traditionally done, except that any materials which are currently known, from an engineering point of view, to be mis-classified should, if possible, be brought into line. Work is reported here that was done at NIST (US) and Forintek (Canada) using the Cone Calorimeter. At NIST and BASF, the test conditions for all specimens involved an irradiance of 75 kW/m2. A classification criterion was then sought which was based on either the peak HRR or the average HRR taken over a certain time period. The data obtained at NIST did not lead to definitive conclusions, but did suggest that the value at which the cut-off criterion could be based was uncomfortably tightly circumscribed. The work undertaken at Forintek was more broadly based. The design was to amend the National Building Code of Canada not merely by re-defining non-combustibility, but rather, by defining "degrees of combustibility". Thus, for example, a logical HRR based category should emerge for rating fire-retardant treated woods (which are currently defined in the codes as a special use category). The work at Forintek involved an exposure level of 50 kW/m2, although some other fluxes were also explored. More materials were included in this study than in the others, and it was possible to carry the conclusions further. The Forintek work showed that while it may be impossible to classify based on a single cut-off value, a satisfactory classification results by considering two variables. The two variables examined are the peak HRR and the total heat released over a 900 s period. Based on such a compound criterion, it was possible to establish classifications which were acceptably consistent with current building code practice.