Limits to the Effectiveness of Metal-Containing Fire Suppressants. Final Technical Report.
Limits to the Effectiveness of Metal-Containing Fire
Suppressants. Final Technical Report.
(1916 K)
Linteris, G. T.
NISTIR 7177; Final Technical Report, March 1, 2004-July
31, 2004; 64 p. October 2004.
Keywords:
metals; fire suppression; additives; iron;
effectiveness; halons; ozone; halon alternatives;
reaction rate; premixed flames; diffusion flames; flame
extinguishment; condensation; flame retardants;
ignition; combustion; nozzles
Abstract:
This report reviews the literature on metal inhibition
of flames and identifies metal species with potential as
fire suppressant additives. To provide a basis for
discussion, the detailed mechanism of inhibition of iron
is reviewed, and the reasons for its loss of
effectiveness are described. The demonstrated flame
inhibiting properties of other metals is then discussed,
followed by a description of the potential loss of
effectiveness for these other metals. The production ban
on the widely used and effective halon fire suppressants
due to their ozone depletion potential, has motivated an
extensive search for replacements. Metal containing
compounds have attracted attention-especially for
unoccupied spaces-because of their extraordinary
effectiveness in some configurations. For example,
Fe(CO)5 has been found to be up to eighty times more
effective than CF3Br at reducing the overall reaction
rate in premixed methane-air flames, when added at low
concentration. Unfortunately, it has also been found to
produce condensed-phase particles which reduce its
effectiveness for co-flow diffusion flames. Hence, it is
of interest to identify other metal compounds which may
be strong flame inhibitors and then to assess their
potential for loss of effectiveness through
condensation. To achieve this goal, the present report
provides background on current understanding of metal
inhibition of flames, identifying metals with fire
suppression potential. The inhibition mechanism of the
iron is described, and the followed by a description of
the reasons why it losses its effectiveness in some
flame systems. The equivalent flame inhibiting species
of other metal agents is then discussed, and evidence
for any potential loss of effectiveness for these other
metals is assembled and discussed.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899