Release Rate Tests for a Mathematical Model

Abstract

A standard ASTM Test Method for Heat and Visible Smoke Release Rates for Materials and Products (E906-83) is used to provide the basic reaction kinetic information for a mathematical model of a developing fire in a compartment. The model, which is a true predictive model, was designed to utilize experimental release rate data in a simple and straightforward manner without assumptions regarding the ideality of burning, the change in release rate with time, or heat flux to the solid surface or the plane of decomposition. The premise on which the model is based may be stated: if (1) release rate characteristics of a material or product are known for the range of conditions to which it is exposed in a real fire situation; and (2) its exposure as a function of time is known or predictable, then the real fire performance of the material or product can be predicted. The fire performance of materials and products are found from release rate tests; the exposure conditions are calculated as a function of time and position using the model. Interpretation of the basic release rate data and reduction to the format required by the model is described. Methods are given for deriving the instantaneous values of release rate from data obtained during the progressive involvement phase of the specimen. Importance of good release rate data to the accurate prediction of a fire's development is illustrated. Several assumptions made in formulating the model have been examined. The flux-time product (FTP) concept, as defined and used in this model, has been tested experimentally and, for the materials checked, has shown to be a useful and reliable indicator of ignition. Cumulative (total) heat release (THR) has also shown to be a good parameter for correlating changes in heat release rate for char-forming materials with changes in flux and time.