Chemically enhanced water mist fire suppression

Abstract

Since the phasing out of halons, water mist systems have gained attention as a possible alternative form of fire suppression. These ultrafine sprays have both advantages and disadvantages compared to conventional water sprinklers. It has been suggested that one way to improve their performance would be to produce the mist from an aqueous solution of a chemical fire suppressant.

Two small-scale experiments were devised to quantify and compare the suppression efficiency of the mists of chemical solutions. Twelve potential chemical suppressants were selected from a review of the literature and delivered into the fires as mists of their solutions at 3-10% m/v concentration; their effect on the time taken to extinguish the flame was recorded. In addition,90 full scale fire tests were conducted to identify how suppression might best be improved with chemical additives, and a mathematical model was constructed to estimate optimum droplet parameters for various conditions.

In the small scale experiments, solutions of KHCO3, other compounds of alkali metals, and seawater showed excellent improvement to the extinction time. On the large scale, a body of research on the comparatively under-studied wood crib fires was compiled, and it was concluded there was scope for using chemically enhanced water mist to provide effective room coverage with fewer nozzles.

This research was original in that it studied a range of chemical suppressants which had largely not been tested in the form of water mist additives; it had an emphasis on the application of the results on real fires, quantifying suppression efficiency by the time taken to suppress a flame; the large scale experiments centred around class A fires; it attempted to provide a wide-ranging and systematic approach to the question of chemically enhanced water mist systems by looking at small scale screening tests, full scale fire tests, and modelling.

Date of Award	Jul 2010
Original language	English
Supervisor	VASILY NOVOZHILOV (Supervisor) & Paul Joseph (Supervisor)