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Fire, Life Safety

Changing airport firefighting foam suppression systems

If aqueous film-forming foam is not good for the environment or our health, why is it still in use?

By Steve Dryden May 13, 2020
Courtesy: Henderson Engineers

If you specify firefighting foams, you have probably heard acronyms like PFAS, PFOS and PFOA recently, but what do they mean? Why are they so bad for the environment and our health? Why can’t we just switch to another option for firefighting?

The primary firefighting foam for airports and aircraft has been aqueous film-forming foam. Unfortunately, AFFF contains perfluoroalkyl and polyfluoroalkyl substances and may contain perfluorooctane sulfonate and perfluorooctanoic acid, the alphabet soup of firefighting foams.

PFAS is classification of chemicals that includes PFOA, PFOS and other chemicals. PFOA and PFOS are dangerous to the environment and to our health because they don’t break down. Instead, they accumulate over time in the environment, the food chain and in humans. The Environmental Protection Agency indicates that exposure to PFAS can lead to adverse human health effects, including chronic health conditions.

The health impacts of these chemicals are still being studied, but the Agency for Toxic Substances and Disease Registry notes that studies have shown these chemicals can interfere with the body’s natural hormones, increase cholesterol levels, affect the immune system and increase the risk of some cancers.

Health and environmental risks

Currently, the Department of Defense requires the use of AFFF for aircraft rescue and firefighting because of its firefighting performance on petroleum-based fires such as aircraft fuel. The Military Specification, known as a MILSPEC, for firefighting foam does not require fluorine foams. However, the performance requirements for these firefighting foams cannot currently be met by nonfluorine-based foams.

MILSPEC 24385 F is the performance specification for AFFF for the military. The specification has requirements for film formation and sealability, stability, compatibility and fire performance. The fire performance requirements include a 30-second extinguishment and a burnback time of 360 seconds. Burn-back requirements include removing a portion of the foam coverage and igniting the foam while observing the time it takes to spread to cover 25% of the pan size.

In 2018, MILSPEC 24385 was updated. One of the changes in this update was the specification no longer requires the foam to contain fluorine. However, at this time, there is not a fluorine-free AFFF that has met the performance of the MILSPEC requirements.

The importance of MILSPEC requirements

The Federal Aviation Administration requires that all airports that adhere to Part 139 Airport Certification use foams that meet military specifications. Part 139 certified airports include most of the commercial airports in the United States. Therefore, since a fluorine-free foam will not meet the MILSPEC requirements, the foams used at the commercial airports around the country still contain PFAS chemicals.

However, in January 2019, the FAA issued a CertAlert on AFFF. The issued recommendation requires that testing of vehicles’ AFFF systems be performed with alternative methods that do not require discharge of AFFF. This guidance allows maintaining and testing the equipment without the expense or environmental impact of an AFFF foam discharge.

The FAA has also set a mandate to stop requiring the use of fluorinated foam no later than Oct. 4, 2021. Research continues on the development of fluorine-free foams that will meet the fire performance required by MILSPEC for these petroleum-based fires.

The fire suppression foam transition

When a foam is developed that is free of the harmful chemicals, the transition can occur, but it is not that simple. Because the chemicals are contaminants, they may have been deposited inside the AFFF systems. Retrofitting ARFF vehicles with new firefighting foam technology may require a minimum cleaning of the system components before introducing new foam. However, conversions in Europe have required extensive remediation. The Department of Defense PFAS Task Force estimates the cost of retrofitting vehicles to range from $30,000 to $200,000 for each vehicle.

Knowing that the United States military has approximately 3,000 vehicles and most airports have at least one vehicle, the cost and effort to retrofit these fire trucks is enormous.

What do we do now?

There is a need to replace fluorine-based foams, however the environmental and health issues with AFFF is not an easy problem to solve. The issue is widespread because AFFF is used almost exclusively for aircraft firefighting by the military and commercial airports in the United States.

Currently, there are no fluorine-free foams that meet the firefighting performance required for petroleum-based aircraft fires by the MILSPEC. However, once an acceptable foam is developed, the contamination of the AFFF systems in the ARFF trucks will need to be addressed.

When the contamination has been mitigated, then we can retrofit the existing ARFF trucks with new foam. While we are not quite there yet, the industry is taking positive steps to create safer conditions for the health of humans and the environment alike.


Steve Dryden
Author Bio: Steve Dryden is a senior fire protection engineer for Henderson Engineers. He is responsible for providing fire and life safety design services, facility assessments and code consulting.