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Aqueous Film-Forming Foams

The US Naval Research Laboratory initiated research and development of firefighting foams in the 1960s to improve fire-suppression performance and increase safety following a devastating fire on the USS Forrestal in 1967. Since this time, the most common means of aviation fire protection involves use of aqueous film-forming foams (AFFFs). Optimized to extinguish jet-fuel fires, AFFFs are water-based foams containing surfactants, substances that reduce the surface tension of liquids in which they are dissolved. When an AFFF is applied to a flammable liquid, a water-based film forms, isolating and cooling the liquid fuel, suppressing formation of flammable vapors, and effectively smothering the fire.

AFFFs work – no doubt about it. Since their deployment and widespread adoption, hangar fires have significantly decreased in frequency. Unfortunately, the foam agents’ undeniable efficiency comes with an array of undesirable side effects. Ironically, the rarity of hangar fires has allowed aviation stakeholders, environmentalists, and insurers the luxury of analyzing and criticizing the many drawbacks associated with use of foam-based firefighting systems.

The most significant risk of AFFF use is, of course, the potential engulfment and asphyxiation hazard to hangar personnel, as illustrated in the Eglin AFB tragedy mentioned above. Fortunately, only one such fatality has been reported to date. The two risk issues most frequently cited by aviation personnel are:

• Frequent accidental discharge of the fire-protection system and subsequent damage to aircraft and equipment
• Environmental hazards from the chemical composition and disposal of the foam agents themselves

Accidental Discharge

There’s no way around it – dousing your sensitive equipment and aircraft in tons of foam will cost you, both in damage to aircraft, maintenance equipment, and other delicate systems, and then in the subsequent cleanup costs. This is true even when the foam successfully extinguishes a fire. You’ve avoided the worst, but you’re still going to take it in the pocketbook. In addition to cleanup costs, a company will experience flight cancellations and reputational damage from an event that will make at least local news. And by “expenses,” we’re talking a lot – one 2018 accidental discharge cost the hangar owner more than $25 million. 

This might be bearable if false-alarm foam accidents were extremely rare or if hangar fires were widespread. The good news, as mentioned, is that actual fires are increasingly rare (though not nonexistent). The bad news is that false alarms are not especially uncommon – some studies suggest about a dozen accidental discharges occur per year. A combination of poor initial design, improper maintenance, and inadequate testing are leading to a rash of false-alarm discharges. The ratio of necessary to unnecessary foam discharges has reached the point that some experts advocate revising NFPA 409 to eliminate automatic foam fire suppression systems altogether, considering the risk of fire not worth the cost of the seemingly inevitable accidents.

Environmental Issues

Attention to industry’s effects on the environment has grown exponentially since AFFFs were first developed more than half a century ago. As you can imagine, AFFF manufacturers have had to evolve their products considerably to keep pace with changing regulations – and, frankly, they’re losing the race.

The first few generations of AFFFs produced significant amounts of perfluoroalkyl substances (PFAS) – hazardous chemicals that:

• Are tough to clean or remove from foam-contacted surfaces,
• Linger a long time in the environment following drainage or other disposal
• Can contaminate soil and drinking water

As environmental consciousness grew over time and more stringent regulations were set, widespread use of PFAS-generating foams became increasingly intolerable. Environmentalists were particularly alarmed by the prevalence of PFOS (perfluorooctane sulfonate), a particularly virulent variant of PFAS, in firefighting foam.

In 2009, the United Nations’ Stockholm Convention on Persistent Organic Pollutants was revised to restrict most use and production of PFOS. This ruling led to modernization of the manufacturing process and the creation of a newer formula that does not contain or break down into PFOS, does not accumulate in the environment, and is nontoxic.

Nonetheless, even this newer telomer-based formula contains trace amounts of PFAS – and under a recent (December 2019) ruling of the US Environmental Protection Agency, trace amounts are all that are needed to investigate potential PFAS contamination and possibly compensate exposed parties under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). In 2021, the Town of Peshtigo, Wisconsin —the site of the deadliest wildfire in recorded human history — sued an AFFF manufacturer for damages related to PFAS contamination, receiving a $17 million settlement.

State and local governments have taken notice of the new guidelines. Approximately 18 states have adopted restrictions on AFFF use, including limitations on training, notification of PFAS content and/or release, storage guidelines, and firefighter personal protective equipment (PPE). The 2020 National Defense Authorization Act (NDAA) stipulates the phaseout of PFAS-containing foams by October 2024. While non-PFAS-containing foams have been developed, they are simply not as effective at extinguishing flammable liquids as their PFAS-bearing counterparts.