Hochiki FirePro Xtinguish, Installation And Operation Manual

Page: 12 / 113

Page 12 of 113
FirePro Xtinguish I&O Manual V1.05 UL
5 Condensed Aerosol Fire Extinguishing Action
Traditionally, there were three distinct elements assumed as necessary for combustion: heat, fuel, and
oxygen, popularly known as the “fire triangle”.
Typical fire extinguishment involves removing the fuel from the fire, limiting oxygen to the fire
(smothering), or removing the heat (quenching).
This physical theory had to be modified as halons became more widely used and better understood.
The halons, as well as other agents like the
FirePro Xtinguish
condensed aerosol, do not extinguish fire
in any of these ways, but instead break up the uninhibited chain reaction of the combustion process.
This extinguishing mechanism is not completely understood, yet there is definitely a chemical reaction
that interferes with the combustion process by removing the active chemical species involved in the flame
chain reaction.
Upon activation, the FPC (patented solid compound contained in the
FirePro
condensed aerosol
generators), immediately starts a chemical reaction that in few seconds produces condensed dry aerosol
in the discharge density defined by the system designer (i.e. potassium compounds, K
2
CO
3
, H
2
O, N
2
,
CO
2
, and other gas particles in small quantities). The condensed aerosol thus generated consists of
micro-sized particles of potassium compounds suspended in inert gases in an extremely high ratio
between the exposed surface and their reaction mass.
The
FirePro Xtinguish
condensed aerosol then remains in suspension for a relatively long time into the
protected volume, allowing its active inhibitor to flow into the combustion core transported by its own
natural convection currents and breaking the chain reaction upon flame contact with extremely high
efficiency.
Potassium is an alkaline metal and requires the least amount of energy for ionization because of its very
low ionization potential. Therefore a certain amount of energy is removed from the combustion itself to
eliminate the atom’s electrons during this ionization process. This is the physical action of the
extinguishing process of
FirePro Xtinguish
condensed aerosol.
The chemical process of the condensed aerosol fire extinguishment is characterized by certain reactions
in rapid sequence taking place between atoms and fragments of unstable molecules, which is called
“chain reactions of radicals”.
Since the radicals are unstable, they tend to reach a final stable condition. The stable final products,
among others, are carbon dioxide (CO
2
) and water (H
2
O).
The potassium atoms derived by the disassociation of the potassium compounds contained in the
FirePro Xtinguish
condensed aerosol, react during combustion with the free radicals of unstable
hydroxides forming potassium hydroxide (KOH), which is a very stable compound.
At this stage the chain reaction of the free radicals is halted and the flame is extinguished.
The reaction sequence is shown on the following page.