Mathematical analysis and possible application of the two-layer zone model FIRM

With the possibility of implementing engineering performance-based fire code, it is important to select a design tool for estimating the fire environment. A simple two-layer zone model such as the ASET model should be a good candidate for quick estimation of fire environment. However, there is no opening in the model and air is supplied through leakage. Another model, FIRM was upgraded from ASET to include a vertical opening. It is believed that it is useful for fire hazard assessment. Mathematical derivation of the key equations in FIRM is reviewed in this paper. Possible application is demonstrated by referring to full-scale burning tests in the new PolyU/HEU Assembly Calorimeter.