Methods for extinguishing fire are generally classified into four types, namely, suppression, cooling, suffocation and removal, and fire extinguishing agents have been developed in accordance with the respective characteristics of the methods. Of these methods, the fire extinguishing by suppression is intended to terminate the chain reaction of combustion by capturing radicals generated in the combustion system, and has the advantage that the required amount of fire extinguishing agent is small as compared to the other methods. As the fire extinguishing agents for the fire extinguishing by suppression, those containing an ammonium salt of phosphoric acid, a halon or the like have been developed.
On the other hand, an epoch-making substance having a combustion suppression effect is reported, which is clearly different from the conventional ones. That substance is metallocene. Ferrocene, which is a type of metallocenes, is useful for the synthesis of various organic compounds; therefore, studies have been made so far as to the use of ferrocene mainly in the field of organic chemistry. Meanwhile, in recent years, it has been reported that ferrocene vapor (sublimate) has a combustion suppression effect (see Non-Patent Document 1). Moreover, it is reported that a filter paper to which a metallocene is attached using a solution of ferrocene or other metallocene in an organic solvent can suppress the combustion and exhibits an excellent combustion suppression effect with much less amount of metallocene than the conventional fire extinguishing agent (see Non-Patent Document 2).
Patent Document 1 discloses a fire extinguishing composition containing ferrocene or a derivative thereof in a content of 25% by weight or more. Further, Patent Document 2 discloses microcapsules containing a fire extinguishing composition comprising an iron-containing compound such as ferrocene and an inert gas source.
Thus, there is a growing expectation about the application of a metallocene to the fire extinguishing agent.