by Joan Leedy, Technical Director
Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals that contain a carbon-fluorine bond. This bond is very strong and as a result, some of these compounds are very stable and do not readily breakdown in the environment. Examples of PFAS molecules of particular concern are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). In the US, PFOA and PFOS are no longer used in firefighting foams but smaller 6-carbon (C6) PFAS molecules are being used instead. Six carbon molecules are thought to be less persistent in the environment and less likely to bioaccumulate in the body if ingested.
PFAS are added to firefighting foam formulations to improve performance. They enable the foam to form an aqueous film when applied to the surface of water insoluble flammable liquids such as gasoline and aviation fuel. The following foams, by definition, contain PFAS:
- Aqueous film forming foam (AFFF)
- Film forming fluoroprotein foam (FFFP)
- Fluoroprotein foam
There are also firefighting foams that have traditionally never contained PFAS. These include:
- High expansion foam used in conjunction with high expansion foam generators. This type of foam is applied at an expansion ratio of 500:1 to 1000:1 and fills an entire enclosure – such as an engine room on board a ship or an aircraft hangar.
- Class A foams, designed to be used solely on class A fires. There are two primary types of class A firefighting foams. Class A foams for use by municipal fire departments for use on structure fires and wildland firefighting foam for use on forest fires.
- Protein foam - Foam made from protein hydrolysate and with no PFAS additives.
In addition, Foam manufacturers are developing PFAS-free foam – defined as Synthetic Fluorine Free Foam (SFFF) in the National Fire Protection Association Standard 11 – Low, Medium- and High-Expansion Foam 2021 Edition. Several SFFF foams are currently listed by Underwriters Laboratory. Also, the U.S. Military recently released a list of foams that meet MIL-PRF-32725 Fire Extinguishing Agent, Fluorine Free Foam (F3) Liquid Concentrates for Land-Based, Fresh Water Applications. QPD Search (dla.mil)
Today, many options exist to design a foam system without PFAS chemicals. Some of the foam manufacturers have even set a date to stop the manufacturing of foams containing PFAS chemicals. Note, the foams are still manufactured with chemicals including surfactants and solvents so when using any foam best practices include the following:
- Check with the local Authority Having Jurisdiction (AHJ) for disposal requirements.
- Train and test in a manner that limits the environmental and toxicological impact.
- Follow the manufacturer’s use recommendations.
If you have a questions regarding this article, please contact Dyne Fire Protection Labs at lab@dyneusa.com or (800) 632-2304.
©Dyne Fire Protection Labs 2023