Extinguishing agents today have to meet many different requirements for aircraft protection. Fire extinguishing agents must be effective on fuel spill fires, engine fires, cause no ‘collateral’ damage to components not involved in the fire and finally, must be environmentally safe.
NFPA 407 Standard for Aircraft Fuel Servicing and NFPA 410 Standard on Aircraft Maintenance has requirements for wheeled extinguishers with a minimum capacity of 57kg of agent and a minimum UL rating of 80B:C.
First let us look at a brief history of fire extinguishing agents for use around aircraft. Since the start of aviation, the search for fire extinguishing agents that are suitable for use around aircraft has been extensive.
Just as aeroplane design and materials have changed greatly, so has the options for fire protection. Starting with water, water fog and then high pressure water mist, chemical foam and foam pellets were all used to have a greater effect on fuel spills involving aircraft. Carbon dioxide became a standby for ramp protection because of its effectiveness on engine fires and its quality of leaving no residue. Chemical foam gave way to protein foam, fluoroprotein foam and then AFFF. Now environmentally-friendly fluorosurfactant-free foams are available for use around aircraft. Foams were found to be useful for spills, but did not answer the question of engine fires or fuel fires in more than two dimensions.
Dry chemical, originally sodium bicarbonate, was found to be effective on spill fires, engine fires and three dimensional fires. Purple-K (potassium bicarbonate) dry chemical took the forefront in the 1960’s after being developed by the U.S. Naval Research Lab in the late 1950s because of its superior effect on flammable liquid fires, when compared with regular dry chemical. It still has the best “knock-down” on a spill fire compared with any other agent, but concerns regarding the powder residue, and detrimental effects on jet engines left many users looking for an alternative. ABC or multi-purpose dry chemical became available in the 1960s but since, has not been used around aircraft because of its corrosive nature to aircraft components.
Enter the Halons, specifically Halon 1211 (bromochlorodifluoromethane), a streaming or vaporising liquid agent that leaves no residue. Similar to dry chemical in its ability to be used on spill fires, three-dimensional fires and engine fires are still in use today using recycled agent. Its harmful effects on the environment, specifically, its ozone depletion potential (ODP) and its global warming potential (GWP) has caused the use of the agent to be curtailed or ceased all together. After the Montreal Protocol, substitutes for Halon firefighting agents were developed. These agent formulas looked to find something that was effective on fire and yet did not have any, or very little, ODP. Many agents of both the streaming and non-streaming types were developed but none of them were as effective on Class B fires as Halon 1211 leaving some end users to hold out for a “drop-in” agent that would be just as effective, kilogram for kilogram as Halon 1211.
The Kyoto agreement turned the ecological impact concerns to global warming potential and atmospheric lifetime of any substitute agents in light of global climate change. Some of the substitute agents were found to have little or no ODP but had atmospheric lifetimes measuring in the thousands of years. All of this brought questions regarding the sustainability of some Halon replacement agents.
Now there is a new firefighting liquid agent, 3MTM NovecTM 1230. The agent is newly available in a UL Listed 3A:80B:C rated wheeled extinguisher using 68kg of 3MTM NovecTM 1230. This agent has an extremely low atmospheric lifetime – in the order of not years or even months, but days (approximately one to two weeks). Studies show that it has zero effect on the ozone layer or zero ODP. The GWP of 3MTM NovecTM 1230 is comparable with CO2, making a case for the agent’s sustainability.
The newest option for meeting the wheeled unit requirements of NFPA 407 and NFPA 410 is now available with both firefighting effectiveness and environmental sustainability. Amerex Corp. is the first fire equipment manufacturer to provide this wheeled extinguisher containing 68kg of 3MTM NovecTM 1230, with a 3A:80B:C listing, readily available for aircraft ramp protection.
For more information, go to www.amerex-fire.com