A mathematical model for estimating available safe egress time in fires

Abstract

A mathematical model for estimating the time available for safe egress from a fire is formulated. The model simulates the conditions which develop during the course of an enclosure fire. Since life safety considerations are primary, the simulation model which is adopted focuses attention only on phenomena which develop between the times of h e ignition and onset of hazardous conditions. This allows significant simplifications in modeling which may not be otherwise justified. Using computed variables of a simulated fire scenario of interest, times of fire detection and onset of hazard which are deduced from realistic detection and hazard criteria would be estimated. The Available Safe Egress Time (ASET) would be defined as the length of the time interval which separates these two events. Quantitative specifications for a variety of detection and hazard criteria are idensed. Results of exercising the model are presented, and ASET estimates are obtained for a wide variety of realistic fire scenarios. A comparison between experimental results of a multi-room fire test and prediction of the single-room model suggest that the model has potentid utility in providing practical simulations of multi-room fire environments.

Experimental and numerical study of furniture fires in an ISO-room for use in a fire forecasting framework

“…This fraction is assumed to be constant as in other fire models [16][17]. Cooper [18] suggests values for λ c in the range of 0.6 to 0.9 for most situations [19]. Mowrer [20] reported a value of 0.7 for a series of fire tests in a relatively large room.…”

A technical reference for CFAST :

“…It is intended as an aid in the fire safety decision-making process. b i coefficients for adsorption and desorption of HCl C flow coefficient for horizontal flow of gas through a vertical vent C LOL Lower oxygen limit coefficient, the fractional burning rate constrained by available oxygen, eq (39) C o characteristic flow coefficient C w wind coefficient -dot product of the wind vector and vent direction CO/CO 2 ratio of the mass of carbon monoxide to the mass of carbon dioxide in the pyrolysis of the fuel CO 2 …”

Fire Research At Nbs: The First 75 Years

“…In the 1970s, zone models involving a collection of coupled process equations began to be developed, notably at NBS and at Harvard University through an NBS grant. Basic CPR contributions in this field include the modeling of: quasi-steady flow in an enclosure [45,46], contribution of the combustible contents [47,48], estimation of safe egress time [49], smoke movement in high-rise buildings [50], and fire growth in multiple compartments [51,52]. An advanced zone model, designated FAST (fire and smoke transport) [53], has been used widely and has been incorporated into an overall "hazard" model which combines models for the movement of occupants and their tolerance to toxic combustion products, with models of fire growth and smoke generation [54].…”