PFAS-free firefighting foam: why replacement is more than a procurement decision

The transition from PFAS-containing to PFAS-free firefighting foam is well underway in Europe. For organisations using fixed or mobile foam fire-suppression systems, this means more than simply selecting and purchasing a new foam concentrate. A different type of firefighting foam may have different physical and flow properties, which can also change the behaviour of an existing fire-suppression system.

The key question, therefore, is not only: which PFAS-free firefighting foam should we choose? Equally important is: does our existing system still perform as intended with this new foam?

Answering that question requires a combination of product knowledge, hydraulic assessment, system knowledge and a well-planned transition.

PFAS is a collective term for a large group of per- and polyfluoroalkyl substances. Various PFAS compounds are highly persistent: they barely break down in the environment and can spread through soil and water, among other pathways.

PFAS have been used for many years in certain types of firefighting foam, including AFFF variants for fighting fires involving flammable liquids. The fluorinated surfactants provide properties that can be effective in forming a fire-suppressing, vapour-sealing layer.

Because of environmental and health concerns around PFAS, European legislation has been introduced that increasingly restricts the placing on the market and use of PFAS in firefighting foam.

From 23 October 2030, the European REACH framework generally restricts PFAS in firefighting foams at a concentration of 1 mg/l or more for the sum of all PFAS. Different transition periods apply to certain uses. For establishments covered by the Seveso Directive, offshore oil and gas installations and certain maritime uses, among others, a relevant exemption runs until 23 October 2035.

23 October 2026 is an important date for organisations that continue to use qualifying PFAS-containing firefighting foam during a transition period.

From this date, additional conditions apply to certain continued uses. Use must be limited to fires involving flammable liquids; emissions and exposure must be minimised; and PFAS-containing stocks and waste streams must, where technically and practically possible, be collected separately and appropriately treated.

In addition, a site-specific management plan for PFAS-containing firefighting foam must be prepared. It must document, among other things, use and volumes present, measures to limit emissions, collection and treatment, cleaning and maintenance, measures in the event of leaks, and a strategy for replacement with fluorine-free firefighting foam. The management plan must be reviewed annually.

23 October 2026 should therefore not be seen as one general deadline by which all PFAS-containing firefighting foam must have been replaced. It is, however, an important milestone for management, documentation and transition planning.

PFAS-free or fluorine-free firefighting foam is often referred to as F3: Fluorine-Free Foam. Unlike traditional fluorinated foams, it does not use fluorinated surfactants to create the required extinguishing properties.

Its performance is achieved with different chemical compositions. Depending on the product, various surfactants, polymers and stabilisers may be used to create a stable foam blanket.

This immediately raises an important technical consideration: a PFAS-free foam is not automatically a one-for-one replacement for the existing product.

Not only firefighting performance can differ. Characteristics such as viscosity, density, foam formation, expansion, drainage, proportioning and flow behaviour may also vary.

When designing a foam fire-suppression system, allowance is made for the characteristics of the foam concentrate that must be transported and proportioned through the system.

The concentrate must be routed from a storage tank or other supply through pumps, piping, valves and proportioning or injection equipment, ultimately entering the firewater stream in the right way. The foam solution must then be delivered through the distribution system to the required discharge points.

For a conventional Newtonian liquid, viscosity at a given temperature is essentially independent of the rate at which the liquid is sheared. Water is the best-known example.

Some PFAS-free foam concentrates behave differently. These products can exhibit non-Newtonian behaviour and may be shear-thinning. With such a liquid, the apparent viscosity decreases as the shear rate increases.

Put simply, the same foam concentrate can behave relatively thickly when flowing slowly, while flowing more easily at higher flow rates.

Research into fluorine-free foams shows that these shear-thinning properties can occur and that polymers in certain formulations, in particular, can have a major influence on flow behaviour.

For a Newtonian liquid, hydraulic calculations can often use one representative viscosity value, provided conditions such as temperature remain the same.

For a strongly shear-thinning foam concentrate, however, one number tells only part of the story. The relevant viscosity may depend on the shear rate occurring at different locations in the system. A liquid may therefore behave differently in a large pipe, a small pipe, a pump or a restriction.

Temperature also plays a role. A system that functions well at a relatively high ambient temperature may show different flow properties at a low temperature.

For a sound technical assessment, rheological data over a relevant range of temperatures and shear rates is therefore preferable to relying solely on one viscosity value from a product sheet.

An existing foam fire-suppression system was designed around certain assumptions: a specific foam concentrate, pipe diameters and lengths, elevation differences, fittings, pumps, proportioning ratios and required flows.

When the original foam is replaced by a PFAS-free product with different flow properties, those assumptions may change. That does not automatically mean the existing system no longer complies. It does mean this must be demonstrated again.

Different viscosity or rheological behaviour can affect pressure loss in concentrate lines, foam pump performance and the operation of proportioning or injection equipment. It must also be assessed whether sufficient pressure and flow are still available at the design discharge points.

Simply replacing the concentrate and assuming the original hydraulic calculation remains valid can therefore present a significant technical risk.

Research into fluorine-free foam solutions also indicates that simple hydraulic assumptions which effectively treat the liquid as water may not be sufficiently accurate for certain non-Newtonian F3 formulations.

When assessing a firefighting system, it is not enough to consider only the most obvious flow path. A fire-protection system must function in the conditions in which it is actually needed. Relevant and governing failure scenarios must therefore also be included.

For example, a particular pipe route or pump may be unavailable, requiring the system to operate through an alternative route. That route may be longer and include more fittings or greater elevation differences, all of which can increase pressure losses.

With a different foam concentrate, such conditions may again become governing. A sound assessment therefore considers not only normal operation but also the hydraulically most unfavourable situations that the system design and safety philosophy require it to handle.

Hydraulics is an important part of the transition to PFAS-free firefighting foam, but it is not the only one.

The remaining components and system assumptions also deserve attention. Consider the suitability and capacity of concentrate pumps, proportioners and injection systems; the required proportioning ratio; material and seal compatibility; storage conditions; temperature limits; and the performance of installed foam makers and discharge devices.

It must also be established whether the new foam is suitable and approved for the specific application and fire hazard present. A product that performs very well in a particular test arrangement is not automatically suitable for every existing system.

The transition should therefore be treated as a system change, not merely as a product change.