Title:
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Chemically enhanced water mist fire suppression
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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.
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