Foam concentrate fire extinguishing performance testing is the core evaluation used to verify that foam agents can reliably suppress liquid fuel fires and resist reignition under standardized fire conditions. This article explains the applicable standards (ISO 7203, EN 1568, UL 162, GB 15308), sample types, key testing items such as extinguishing time and burnback resistance, test methods, typical applications, and frequently asked questions for manufacturers and fire protection engineers.
Technical Overview
Foam extinguishing agents (foam concentrates) are chemical concentrates that, when mixed with water and aspirated through suitable equipment, produce a foam blanket that suppresses Class B flammable liquid fires through smothering, cooling, vapor suppression, and — for film-forming agents — the formation of an aqueous film on the fuel surface. Because foam performance cannot be reliably predicted from chemical composition alone, fire extinguishing performance testing is mandatory for product certification, listing, and regulatory acceptance in most markets.
Fire extinguishing performance testing subjects a generated foam to controlled, reproducible liquid fuel fires in standardized pans, using defined foam generation equipment, application rates, fuels, and preburn times. The tests quantify how quickly the foam controls and extinguishes the fire, how well the foam blanket seals against vapor release, and how effectively it resists burnback when the fuel is deliberately reignited. These fire tests are typically performed together with supporting measurements of foam expansion ratio and drainage time, which strongly influence extinguishing behavior.
The principal international and national frameworks include the ISO 7203 series (foam concentrates for hydrocarbon and polar solvent fires), the EN 1568 series (parts 1 to 4 covering protein, fluoroprotein, AFFF, and FFFP concentrates), UL 162 (foam equipment and liquid concentrates in North America), and GB 15308 (the Chinese national standard for foam extinguishing agents). Testing is carried out by accredited third-party laboratories under controlled conditions to ensure repeatability and mutual recognition of results.
Testing Samples
Aqueous Film-Forming Foam (AFFF and AR-AFFF) Concentrates
AFFF concentrates form a thin aqueous film on hydrocarbon fuels, enabling fast extinguishment even with low-expansion, poorly aspirated foam. Alcohol-resistant AR-AFFF additionally contains polymers that create a protective membrane on polar solvents. Samples are typically submitted at nominal 1%, 3%, or 6% mixing ratios, in both as-manufactured and thermally conditioned states, and are tested with fresh water and, where applicable, seawater.
Protein and Fluoroprotein Foam Concentrates (P, FP, FFFP and AR Variants)
Protein-based foams derived from hydrolyzed protein produce tough, heat-resistant blankets valued for fuel tank protection and subsurface injection. Fluoroprotein (FP) and film-forming fluoroprotein (FFFP) concentrates offer improved fluidity and faster extinguishment, while alcohol-resistant versions extend applicability to water-miscible fuels. These concentrates are the primary subjects of EN 1568-1, EN 1568-2, and EN 1568-4 fire performance testing.
Synthetic Medium- and High-Expansion Foam Concentrates
Hydrocarbon surfactant-based concentrates generate medium-expansion foam (expansion ratio approximately 20:1 to 200:1) and high-expansion foam (above 200:1), used for flooding enclosed spaces such as warehouses, hangars, and cable tunnels. These products are evaluated under ISO 7203-2 and equivalent national schemes using filled-volume and extinguishing tests appropriate to their application.
Class A Foam and Wetting Agent Concentrates
Class A foams reduce the surface tension of water to improve penetration into combustible solid materials. While their principal tests address wetting, penetrating, and ignition suppression on Class A fuels, some products are also evaluated for incidental Class B performance, particularly for wildland-urban interface and municipal applications.
Testing Items
Depending on the product type and the target standard, a typical fire extinguishing performance test program includes the following items:
- Fire extinguishing time: the time from the start of foam application to complete extinguishment of the standard pan fire, with intermediate control (e.g., 90% or 99% control) points recorded.
- Burnback resistance: the time for flames to spread over a defined fraction (commonly 25%) of the fuel surface, or for full-surface involvement, after a burning fuel charge is placed in the extinguished foam blanket.
- Foam expansion ratio: verification that the foam falls within the low (below 20:1), medium (20:1 to 200:1), or high (above 200:1) expansion category claimed by the manufacturer.
- 25% drainage time: the time for 25% of the foam liquid to drain from the generated blanket, an indicator of foam stability and water retention.
- Film formation and sealability: assessment of film spreading behavior and resealing after deliberate foam disturbance for film-forming agents.
- Polar solvent extinguishing performance: extinguishment and burnback on water-miscible fuels such as isopropanol or acetone for alcohol-resistant products.
- Application rate verification: confirmation of extinguishment at the standard application density, for example approximately 2.5 L/min/m² under the EN 1568 fire test method.
- Influence of water quality: performance with fresh water and standard synthetic seawater.
- Concentration tolerance: fire performance at nominal, over-, and under-concentrated mixing ratios.
Testing Methods
Fire Extinguishing (Pan Fire) Test
The core test uses a calibrated circular or square fire pan, filled with a defined depth of standard reference fuel such as n-heptane or unleaded gasoline floating on a water bottom. The fuel is ignited and allowed to preburn for a standardized period, typically 60 seconds, so that the fire reaches a steady burning state. Foam is then generated with a standard nozzle or branch pipe at a controlled application rate — approximately 2.5 L/min/m² under EN 1568 — and applied uniformly across the burning surface. The laboratory records the time to flame control, the time to complete extinguishment, and whether any sustained reignition occurs. Acceptance thresholds and performance classifications differ between EN 1568, ISO 7203, UL 162, and GB 15308, so the test plan must be matched to the market in which the product will be sold.
Burnback Resistance Test
Immediately after extinguishment, the foam blanket is challenged by a burning charge of fuel, typically a lighted crucible or pot placed at the center of the pan. The laboratory measures the time until flames spread over 25% of the fuel surface or until the entire surface is involved, depending on the standard. Burnback time demonstrates the capacity of the foam blanket to withstand direct flame impingement and resist reignition of flammable vapors, which is critical for fixed protection systems on storage tanks and process vessels where prolonged foam integrity is required.
Expansion Ratio and Drainage Measurement
Standardized foam generation equipment produces foam under fixed pressure, flow, and temperature conditions. The expansion ratio is calculated from the mass of foam filling a calibrated volumetric vessel relative to the mass of the corresponding foam solution. The 25% drainage time is then measured by collecting the liquid drained from a known volume of foam. These bench-scale results are reported alongside the fire data because they explain, in part, the extinguishing behavior observed in the pan tests and are used by standards bodies as classification parameters.
Film Formation and Sealability Tests
For AFFF and FFFP concentrates, film-forming capability is evaluated by spreading coefficient determinations derived from surface and interfacial tension measurements, and by practical sealability observations on a fuel surface. After the foam blanket is partially removed or disturbed, the laboratory observes whether the aqueous film reseals the exposed fuel quickly enough to prevent reignition when an ignition source is applied. This capability distinguishes film-forming agents from conventional protein foams.
Polar Solvent Fire Tests for Alcohol-Resistant Foams
Alcohol-resistant concentrates are additionally tested on water-miscible fuels such as isopropanol, acetone, or defined alcohol-water mixtures, in which ordinary foams are destroyed rapidly. The test protocol follows the pan fire and burnback logic described above but with polar solvent fuel layers. Successful extinguishment confirms that the polymer membrane formed by the AR concentrate effectively protects the foam blanket from solvent attack, as required by ISO 7203-3 and the corresponding clauses of GB 15308 and UL 162.
Water Quality, Concentration, and Conditioning Robustness
To establish practical reliability, the fire tests are frequently repeated with synthetic seawater, at mixing concentrations above and below nominal, and on samples that have undergone thermal conditioning or aging representative of storage life. Robust performance across these variables supports long-term field reliability and is often a condition of product listing or certification.
Applications
Petrochemical and Oil and Gas Facilities
Certified foam concentrates are specified for storage tank farms, loading terminals, process units, and dike protection, where extinguishing time and burnback resistance directly determine the sizing of foam proportioning systems and foam concentrate reserves. Test data allow designers to verify that system design application rates meet or exceed the critical rates demonstrated in the laboratory.
Aviation and Marine Fire Protection
Aircraft rescue and firefighting vehicles, hangar deluge systems, and marine machinery space and deck protection systems rely on fire-tested foam. Regulatory acceptance in these sectors typically requires extinguishing and burnback evidence generated under internationally recognized standards, together with seawater compatibility data for marine installations.
Warehouses and Enclosed Spaces
Medium- and high-expansion total flooding systems protect warehouses, roll paper storage, cable tunnels, and aircraft hangars. The supporting test evidence confirms filling performance and extinguishing capability in confined geometries characteristic of these applications.
Product Certification and Regulatory Compliance
Manufacturers submit concentrates to accredited third-party laboratories to obtain product certification, listing marks, and market access. In addition, the ongoing transition toward fluorine-free foam concentrates — driven by restrictions on per- and polyfluoroalkyl substances — has increased demand for extinguishing performance testing to demonstrate that replacement agents meet the same fire performance expectations as legacy AFFF products.
FAQ
What is the difference between extinguishing time and burnback time?
Extinguishing time measures how quickly the foam suppresses an established fire, measured from the start of foam application to complete flame extinguishment. Burnback time measures how long the extinguished foam blanket resists reignition after a burning fuel charge is introduced, reflecting the durability and vapor-sealing ability of the blanket. Both are required for classification under EN 1568, ISO 7203, UL 162, and GB 15308.
Which standards govern foam extinguishing performance testing?
The most widely applied standards are the ISO 7203 series for foam concentrates on hydrocarbon and polar solvent fires, the EN 1568 series (parts 1 to 4) for protein, fluoroprotein, AFFF, and FFFP agents, UL 162 for the North American market, and GB 15308 in China. The applicable standard depends on the product type, expansion class, and the target market.
Why are expansion ratio and drainage time reported with fire test results?
Expansion ratio and 25% drainage time characterize foam quality and stability, which directly influence how the foam flows across a burning fuel surface and how much liquid it retains for sustained vapor suppression. Standards use these parameters to classify foams and to contextualize extinguishing and burnback performance.
Do the tests use fresh water or seawater?
Most standards specify testing with standard fresh water by default, and many product approvals add testing with standard synthetic seawater because marine and coastal installations may only have seawater available. Alcohol-resistant and certain listed products must demonstrate performance with both water types in many schemes.
Can fluorine-free foam concentrates be tested under the same procedures?
Yes. Fluorine-free foam concentrates are evaluated using the same pan fire, extinguishing, and burnback methodologies, allowing direct comparison of fire performance against incumbent film-forming agents. Accredited third-party laboratories routinely conduct such comparative assessments to support substitution decisions and regulatory submissions.
How are alcohol-resistant foams evaluated differently?
Alcohol-resistant concentrates undergo additional pan fire and burnback tests on polar solvents such as isopropanol and acetone, in which conventional foams collapse. The tests verify that the polymer membrane produced by the concentrate protects the foam blanket and sustains extinguishment on water-miscible fuels.