Explain why active opening of windows can mitigate fire spread in modern building compartments

Abstract

Modern buildings are now usually designed of large open-plan space and large glass windows. Differing from the conventional small compartment fires of limited ventilation, compartment fires in modern buildings are likely to exhibit a localized fire travelling along the floor plan without flashover. Noted that windows were assumed as initial openings in such fire tests aiming for travelling fire behavior, which is justified by early-stage glass breakage in fires. In this paper, the effect of window glass to fire development has been questioned and investigated, which is followed by the data analysis to understand the fire mitigation mechanisms of a novel ‘active opening’ strategy. It is a counter-intuitive strategy to actively open glass windows after detecting a fire, with the purpose of mitigating fast fire spread. Two scaled compartment fire tests have been conducted, as the first ever experimental evidence pointing out the strikingly different fire development paths due to glass existence and active opening. The corresponding CFD fire models have been established with validation to provide more comprehensive information for understanding the interaction mechanisms. By analyzing the histories of heat release rate, smoke characteristics, and floor heat fluxes, it is found that the localized fire at early stage could not create fall-off of the window glass to form ventilation, and the expected smoke venting occurs until the fire flames rapidly spread. Through the analyses, it has proved that actively opening windows could effectively reduce the smoke thickness and temperature, reducing the heat radiation to the adjacent floor fire load. While not intensifying the growth of localized fire, the active opening strategy could immediately reduce smoke accumulation, and successfully prevent fire spread. These would ultimately ensure the safety of people, reduce the damage to building structures, and facilitate firefighting.