Firefighting Foams Selection and Use
Achieving a balance of performance and sustainability
Firefighting foam is a suppression medium known for its effectiveness in preventing, extinguishing or controlling fires involving flammable liquids (Class B fuels). In recent years there has been significant discussion within the fire protection industry and related fields about the importance of mitigating potential environmental degradation caused by the discharge of firefighting foams containing fluorine. Fire Protection Association Australia (FPA Australia) recently completed and published an information bulletin entitled The Selection & Use of Firefighting Foams that details important factors that must be considered when selecting foam for use on fixed or portable firefighting equipment in Australia.
This article outlines the background to firefighting foams, the Association’s position and considerations for the future, as detailed in the Information Bulletin.
Firefighting Foams – The Story So Far
Firefighting foam has been used in the extinguishment of fires since it was created by Russian Engineer and Chemist, Aleksandr Loran, in 1902. While water has long been understood to be the universal agent for suppressing fires, it is ineffective on some fire types such as oil fires, and can even be dangerous. For fires such as these firefighting foams represented a positive development in effective extinguishment and are still the most widely used method of combating such fires.
Firefighting foam is produced by mixing foam concentrate with water to produce foam solution. This solution can either be applied:
- Non-aspirated: (through water nozzles, sprinklers or deluge nozzles – provided the foam is suitable for application through these devices); or
- Aspirated: (when the foam solution is mixed with air through dedicated foam making devices including foam branch-pipe, top pourer, foam cannon, foam sprinkler, medium expansion pourer or high expansion generators).
The application of firefighting foams suppresses liquid fuel fires by suppressing the release of flammable vapours, separating flames from the fuel, blocking the supply of oxygen to the fuel and cooling the fuel.
Firefighting foams can be broken into two broad categories: Foams that contain fluorinated surfactants; and foams that are fluorine free. However there are also individual foam types within these two broad categories.
Commonly used firefighting foam types are better known by the following terms:
- Fluorinated Firefighting Foams: AFFF (aqueous film-forming foam), FFFP (film forming fluoroprotein), AR-AFFF (alcohol-resistant aqueous film-forming foam), AR-FFFP (alcohol-resistant film-forming fluoroprotein), and FP (fluoroprotein foam).
- lFluorine-free Firefighting Foams: F3 (fluorine-free foams).
Fluorinated Firefighting Foams
Historically, fluorinated firefighting foams include perfluorinated and polyfluorinated chemicals (PFCs). Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are two of the best know PFC-based firefighting foams.
Fluorinated firefighting foams that contain PFOS and PFOA have good firefighting performance but have been identified as having a negative effect in the environment due to their chemical composition. PFOS and PFOA fluorosurfactants are manufactured by a process called electrochemical fluorination (ECF). Other fluorosurfactants can be made with a different process known as telomerisation and are known as fluorotelomers or telomer-based fluorosurfactants.
Fluorinated firefighting foams that contain fluorotelomers do not contain PFOS and only trace levels of PFOA.
In 2004 the first 12 persistent organic pollutants (commonly referred to as POPs) were listed in annexes to the Stockholm Convention. The Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty (that Australia is a signatory to) that aims to eliminate or restrict the production and use of persistent organic pollutants. In 2010, PFOS was one of nine new substances added as an Annex B restricted substance in accordance with the Stockholm Convention with the expectation that every four years progress on its elimination is reported. It should be noted that Australia’s National Implementation Plan for the Stockholm Convention was published by the Commonwealth Department of the Environment prior to the addition of PFOS as a POP.
Australia is yet to ratify this addition of PFOS as an Annex B restricted substance and update the National Implementation Plan to reflect this. Australia is considering ratification of PFOS as a POP but must go through a domestic treaty process that the Commonwealth Department of the Environment is responsible for. FPA Australia considers that the Australian Government should ratify PFOS as a POP in accordance with the Stockholm Convention and the Association has provided information to support this. With the goal of reducing and ultimately eliminating production and use of PFOS, the Stockholm Convention encourages:
- Phase out of use when suitable alternative substances or methods are available.
- Producers or users of PFOS to develop and implement an action plan for elimination.
- Producers or users, within their capabilities, to promote research on development of safe alternative substances to reduce human health risks and environmental implications.
The European Union (EU) has prohibited the marketing and use of PFOS since 27 June 2008 as it met the PBT criteria relating to persistence (P) and toxicity (T) and very high bioaccumulation (B) in aquatic organisms has been proven. PFOS was banned from use in 28 European countries in 2011, requiring high temperature incineration (above 1,100°C) to destroy it.
However, it is misleading and untrue to suggest that other fluorinated chemicals (produced by a different, telomerisation process producing fluorotelomer surfactants) will behave in a similar way and thus have similar negative environmental impacts.
While it is a substance of concern, PFOA is orders of magnitude lower in its bioaccumulation and toxic effects than PFOS. Scientific research has shown that C8 and longer chain fluorochemicals are larger more complex molecules that are more likely to breakdown to substances that become toxic, potentially bioaccumulate, and remain in mammalian organisms for longer periods of time.
PFOA is found as an unintended by-product of the fluorotelomer reaction process as trace quantities in eight carbon chain (C8) or longer fluorotelomer surfactants. In 2005, concerned about the known persistence of PFOA in the environment, detection in human blood and effects in animal studies, the US Environmental Protection Agency (EPA) and eight important fluorotelomer manufacturers launched a voluntary PFOA Stewardship Program to phase out these small amounts of PFOA, and the precursor chemicals that can break down to PFOA, from their production processes, waste streams and finished products by the end of 2015. Most Australian distributors of foam are aligned to this stewardship program.
In 2013, the Danish Environmental Protection Agency compiled a survey of PFOS, PFOA and other perfluoroalkyl and polyfluoroalkyl substances. It confirmed that the technologically best alternatives to long-chain fluorinated chemicals are short-chain chemicals with a carbon chain length of ≤C8 for perfluoroalkyl carboxylates and ≤C6 for perfluoroalkyl sulfonates. The short-chain fluorinated alternatives are still rather persistent but much less bioaccumulative and toxic than the long-chain homologues.
By way of an example, The Danish EPA’s overall conclusions confirmed that the US EPA PFOA Stewardship Program will result in significantly lower environmental concentrations and human exposure to these chemicals in the future.
The short-chain homologues have a better toxicological profile and do not bioaccumulate to the same extent as the long-chain substance as they are excreted more rapidly from both humans and organisms in the environment, but they are still persistent in the environment. The short-chain homologues and their precursors (for example, fluorotelomers based on short-chain fluorochemistry) generally seem to have a better human health and environmental profile than the substances based on long-chain fluorochemistry.
The French Food Safety Agency and Norwegian Institute of Public Health have evaluated the potential human health risks related to the residual presence of PFOA in non-stick coatings for cookware, concluding that the consumer health risk is negligible.
Scientific research into six carbon atom and shorter (≤C6) chain fluorotelomer surfactants and their primary breakdown products of 6:2 fluorotelomer sulfonate (6:2 FTS) and perfluorohexanoic acid (PFHxA), have shown that although still persistent, firefighting foams containing C6 fluorotelomer surfactants are neither bioaccumulative, nor genotoxic, nor developmental toxins. They are not mutagenic, nor have they been shown to exhibit harmful effects. They have been preferentially found in aquatic sediments, are generally an order of magnitude less toxic to aquatic life than fluorine-free foam (F3) alternatives, with lower chemical oxygen demands (COD) during biodegradation. Accordingly, foam manufacturers have recently begun producing fluorinated firefighting foams containing fluorosurfactants that have only four to six carbon atoms, improving environmental properties and complying with the US EPA PFOA Stewardship Program.
- C6 Fluorotelomer-based Foams
These foams do not break down into chemicals currently listed or suspected of being POPs and are not listed by the Stockholm Convention or European Chemicals Agency current (2014) list of substances of very high concern (VHC). They also do not contain or break down into PFOS and are not made with PFOA or any PFOA-based products. Additionally, foams of this type are not made with chemicals currently considered to be bioaccumulative or toxic by environmental authorities. However fluorotelomer surfactant based firefighting foams still retain strong firefighting performance.
Most fluorotelomer surfactants have chemical composition, breakdown products and environmental impacts that are very different from PFOS without the far reaching bioaccumulative and toxic environmental impacts. This is evident in the shorter chain C6 fluorotelomer surfactants increasingly used in modern fluorinated foams.
Given the above information, it is clear that fluorinated firefighting foams should not be grouped as a single class in terms of their environmental properties. Foams containing PFOS, PFOA and fluorotelomers have distinctly different environmental characteristics and these sub-groups must be considered separately on the basis of these characteristics.
Fluorine-free Firefighting Foams
In recent years, driven by the European and US reforms, fluorine-free foam technology has advanced in order to counter concerns raised with PFOS and PFOA fluorinated foams. Fluorine-free foams are now available in the Australian and international market.
It is important to note, however, that just like fluorinated foams, not all fluorine-free foams are the same. For example, where hydrocarbon surfactants have been used to replace fluorosurfactants, some fluorine-free foams have been shown to be an order of magnitude higher in acute aquatic toxicity than fluorotelomer-based foams.
FPA Australia supports the use of more environmentally responsible foam formulations. However, firefighting foams must only be used in applications where they provide acceptable firefighting performance and safety.
Historically, there are a number of important applications for which fluorine-free foams have not been suitable. These include portable fire extinguishers and non-aspirated pre-engineered foam/water spray systems used to protect large mining machines.
Use of foam in these applications in Australia requires the extinguisher/system to pass specific fire test protocols detailed in Australian Standards AS/NZS 1850 (Portable fire extinguishers – Classification, rating and performance testing) and AS 5062 (Fire protection for mobile and transportable equipment) respectively. Past testing has demonstrated that fluorine-free foams have been ineffective on the fires specified in the test protocols and hence have been unsuitable for use in these applications. Regardless of the type of foam, fluorinated or fluorine-free, foams should not be used in any application unless the required fire test protocols have been successfully passed or completed.
As with fluorinated firefighting foams, fluorine-free firefighting foams should not be grouped as a single class in terms of their environmental properties or performance. High detergent content in some fluorine free foams can make them vulnerable to edge flickers, sudden flashbacks and re-involvement that can put the safety of firefighters at unnecessary risk. Some fluorine-free foams have proven firefighting performance, but just like fluorinated foams, evidence of suitability for purpose must be demonstrated.
The Fire Protection Association Australia’s information bulletin entitled The Selection & Use of Firefighting Foams was created with significant input from a range of stakeholders including major end users, foam manufacturers and the Association’s own technical committees and contemporary local and international research papers.
Looking to the Future – Some Recommendations
FPA Australia’s recommendations on the selection and use of firefighting foam are as follows.
Based on the scientific research undertaken it is the position of FPA Australia that the use of foams containing PFOS should be banned. Additionally, the Association recommends that existing stocks of foams containing PFOS should be removed from service and sent for high temperature incineration at an approved facility.
Foam manufacturers should reduce and eliminate the production of foams containing PFOA in accordance with the US EPA PFOA Stewardship Program.
Critically, regardless of whether the foam under consideration is a fluorinated or fluorine-free foam, evidence of suitability must be provided to demonstrate its ability to achieve the required firefighting performance for the fuel in question, having been subjected to appropriate and recognised testing. Evidence of suitability must also be used to demonstrate that the foam is compatible with associated systems and equipment.
The Association takes the view that, while environmental considerations are important, the environmental performance of foam cannot be used as the sole selection criteria. In addition to being tested and deemed to be fit for purposes as outlined above, the Association recommends the following additional key selection criteria be considered when selecting firefighting foam:
- Life safety.
- Physical properties and suitability for use on known hazards.
- Compatibility with system design and approvals.
Any proposal to change the type of foam used in a system requires careful consideration and must take fire safety and engineering factors into account. The type of foam used should not be changed without completing a detailed review of the design, performance and operation of the system as a whole. Such design reviews should include consultation with fire system designers, foam and foam hardware suppliers, and the relevant authority having jurisdiction.
Choosing the most responsible firefighting foam, the best one to protect people, property and the environment, involves selecting one that provides a combination of firefighting performance, reliability and life safety, balanced with minimal toxicological and environmental impacts.
This article contains extracts from IB-06 Selection and Use of Firefighting Foams. To view the full document, visit www.fpaa.com.au/technical and select Technical Documents. More information is available by contacting the FPA Australia Technical Department on 1800 731 922.
Joseph Keller is Communications Manager at FPA Australia.
Matthew Wright is Chief Technical Officer and Deputy CEO.
For further information, go to www.fpaa.com.au