17.1.1 Introduction

The progress of a fire is often divided into three phases consisting of:

1. ignition and early development,

2. total involvement, and

3. fire recession and extinguishing.

The temperature profile of such processes is depicted schematically in Figure 17.1.

Figure 17.1: Temperature/time fire profile (a) Fire development phase; (b) Fully developed fire; (c) Receding fire. ( Source Author's own files)

The fire characteristics of a material are characterised by ease of ignition, contribution to flame spread, and heat contribution, as well as other factors generally associated with fires, including smoke density and toxicity and corrosiveness of the combustion by-products. Fire behaviour, however, cannot be considered a material property because it is markedly affected by both material and environmental factors. These include the distribution of material in the room, material geometry and other physical factors, temperature history, thermal conductivity, intensity and type of ignition source, exposure time to the ignition source, integration of the material, and ventilation effects [1 3]. The varying nature of the fire risk situation and the influence of materials and environmental factors make it very difficult to establish tests and ratings criteria that would be generally applicable. That is, no doubt, one of the main reasons that many different tests have been developed in research and industry and by regulatory agencies. Many of these, in part material-specific, procedures serve well as quality control or developmental guideposts. The results obtained from within the regime of a test standard are, at best, of...