Halon 1301 is installed and used in fixedflooding systems for extinguishing flammableliquid fires. Halon 1211 is not used in totalflooding systems. Its lower volatility, plus a highliquid density, permits the agent to be sprayed asa liquid and therefore propelled into the fire zoneto a greater extent than is possible with othergaseous agents. Halon 1211 will replace Purple-K-Powder (PKP) in twin-agent systems installedon mobile fire-fighting apparatus on aircraftcarriers.Steam. Steam smothers a fire by reducingthe concentration of oxygen or the gaseous phaseof the fuel in the air to the point that combustionstops. As long as the steam blanket is maintained,it will prevent reignition.Since steam is a vapor when applied, itprovides little cooling. Additionally, steamcondenses when its supply is shut off. Its volumedecreases rapidly and combustible vapors and airrush in to replace it. A fire can reflash if it hasnot been completely extinguished and cooled. Thetemperature of steam itself is high enough toignite many liquid fuels. Steam is hazardous topersonnel because the heat it carries can inflictsevere burns.Dry Chemical Extinguishing Agent. PKPis a dry chemical principally used as a fire-extinguishing agent for flammable liquid fires. Itis used in portable extinguishers and handheldhose-line systems aboard ship.Various additives are mixed with PKP basematerials to improve their storage, flow, andwater-repellency characteristics. The most com-monly used additives are silicones, which coat theparticles of PKP to make them free flowing andresistant to the caking effect of moisture andvibration.When PKP is applied to fire, the dry chemicalextinguishes the flame by breaking the combus-tion chain. PKP does not have cooling capability.When PKP is applied, an opaque cloud is formedin the combustion areas. This cloud limits theamount of heat that can be radiated back to theheart of the fire. Less fuel vapor is producedbecause of reduced radiant heat.PKP attacks the chain reaction required tosustain a fire. It is believed that PKP reduces theability of the molecular fragments to recombine,thereby breaking the chain reaction.PKP is primarily used to extinguish flammableliquid fires but can also be used on electrical fires(class C). PKP is highly effective in extinguishingboth flammable liquid pool fires and oil sprayfires. Although PKP can be used on electricalfires, it will leave a residue that may be hard toclean. PKP can be used in the galley for fightingfires on such items as the cooking hood, ducts,and ranges.WARNINGThe ingredients presently used in PKP arenontoxic. However, the discharge of largequantities of PKP may cause temporarybreathing difficulty during and immediatelyafter discharge and may seriously interferewith visibility.The following is a list of limitations for PKPuse.1.2.3.4.5.6.PKP is not effective on materials that con-tain oxygen.PK should not be used in installationswhere relays and delicate electrical contactsare present.PKP is not effective on combustible metalsand may cause a violent reaction.Where moisture is present, PKP may com-bine with the moisture to corrode or stainsurfaces on which it settles; when possible,PKP should be removed from all surfaces.PKP does not produce a lasting inert at-mosphere above the surface of a flammableliquid; consequently, its use will not resultin permanent extinguishment if ignitionsources such as hot metal surfaces orpersistent electrical arcing are present.PKP is not effective on fires involvingordinary combustibles (class A). However,it can be used to knock down a flamingfire, keeping it under control, until hoselines are advanced to the scene.Aqueous Potassium Carbonate. Aqueouspotassium carbonate (APC) is used aboard shipsfor extinguishing burning cooking oil and greasein deep fryers and galley ventilation exhaust ducts.An APC solution consists of 42.2 percent K2CO3and 57.8 percent water. Alkaline solutions suchas APC are often used in combating liquid greasefires involving unsaturated animal fat and7-13
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