Finding and Understanding the Limiting Oxygen Concentration for Oxygen Reduction Systems

Abstract Automated storage systems and large-scale freezers can be challenging for conventional fire protection systems. Instead, an oxygen reduction system (ORS) could be a suitable option. In an ORS the design oxygen concentration is the key parameter for the level of protection achieved by the system. However, current methods for determining this concentration yield varying results and either require large and complex test setups or arrive at overly optimistic levels for protection. In this paper, an experimental method for using the controlled atmosphere cone calorimeter (CACC) to find the limiting oxygen concentration at extinction (LOC ext ) is proposed. The results from the CACC showed good agreement with limiting oxygen concentrations (LOC) determined by large-scale; indicating that the CACC could serve as a cost-effective alternative for determining the LOC of ordinary combustibles for ORS applications. Furthermore, thermal analysis and experiments using both nitrogen and carbon dioxide highlights that the thermal properties of the diluent gas, rather than oxygen displacement and chemical quenching, are the primary factors influencing the LOC. Hence, the findings in this paper increase the understanding of ORS systems and offer a way to determine the LOC for ORS based on small-scale testing.