The transport and remote oxidation of compartment fire exhaust gases

Abstract

The majority of deaths and injuries in compartment fires result from inhalation of the toxic gas, carbon monoxide (CO), especially in locations remote from the burning compartment. This causes the transport and oxidation of CO in burning buildings to become an important topic. Studies have been conducted to determine the toxic environments produced inside, and in locations remote from, a burning compartment; however, no studies have investigated the composition of the exhaust gases during transport to remote locations. The goal of this study was to investigate fire exhaust gas transport through a hallway to determine the important parameters affecting the efficiency of sustained external burning in oxidizing toxic gases, including the hydrodynamic effects of different hallway configurations.

Underventilated compartment fire experiments were performed with a compartment exhausting along the axis of a hallway. The design of the compartment allowed direct measurement of the global equivalence ratio which was used as a main correlating parameter. Characteristic global equivalence ratios and an ignition index concept were investigated to determine when sustained external burning would occur. Gas sampling was performed downstream of the hallway to determine the overall efficiency of sustained external burning, and in the hallway to provide detailed data on the processes occurring in the hallway.

The oxidation of the exhaust gases traveling through the hallway was determined to vary among different species, and also to be very sensitive to the hydrodynamic mixing between the rich exhaust plume and the cooler ambient air in the hallway. In general, the overall oxidation of hydrocarbons was much more complete than for CO or soot. The gas temperatures in the hallway and fuel vaporization rate were also determined to affect oxidation in the hallway. Variations in the hallway inlet and exit soffits affected the hydrodynamic structure of the exhaust plume and oxidation efficiencies, with the inlet soffit exhibiting the strongest effect.