Engineering performance of water mist fire protection systems with antifreeze

The use of antifreeze in water mist fire suppression systems offers a potential alternative to the current applications of these systems in subfreezing environments. Design and development of these systems, however, requires quantitative data detailing the effect of antifreeze on factors, such as small droplet sizes and/or higher system pressures which is currently unavailable. This study investigates the use of antifreeze, of various chemical compositions and concentrations, in water mist systems by quantifying variables that affect spray characteristics, indicate the potential risk of system failure, and evaluate the interactions of the discharged agent with the fire. Extensive testing and analysis demonstrate that no tested antifreeze solution behaves ideally with respect to quantified variables. Some of the antifreezes tested should not be used above a certain concentration in high-pressure water mist systems due to solution flammability and the resulting contribution to the heat release rate of the fire. The impact of all other tested pressure and concentration combinations is less significant on the heat release rate of the fire. Therefore, solutions used at these respective pressures and concentrations are potentially suitable for use in water mist systems unless spray performance or the potential risk of system failure discourages their use. Ignitibility of the antifreeze discharge was proven to be a function of antifreeze solution concentration and droplet size. Future testing should determine the threshold droplet size for ignition of the antifreeze discharge and at what point changes in solution properties begin to significantly impact droplet size in subfreezing environments.