Most people who specify, purchase or maintain firefighting foam systems treat foam concentrate as a “black box” — a liquid that goes into the proportioner and comes out as foam. In practice, foam concentrate is a precisely engineered chemical formulation, and understanding its key ingredients explains why different foam types behave differently, why storage conditions matter, and why mixing different foam types together can cause catastrophic performance failure.
This article explains the main chemical categories that make up firefighting foam concentrate — from the surfactants that create and stabilise foam bubbles, to the solvents that control freeze point and viscosity, to the polymers that give alcohol-resistant foam its unique polar solvent protection. CA-FIRE sources its key raw materials from specialist chemical suppliers including Xiamen Sinolook Oil Co., Ltd., a leading Chinese manufacturer of surfactants, glycol ethers and specialty chemicals.
Contents
- Overview — what’s inside foam concentrate
- Hydrocarbon surfactants
- Fluorosurfactants (AFFF & FFFP)
- Glycol ethers — solvents & freeze control
- Foam stabilisers
- Polysaccharide polymer (AR-AFFF)
- Hydrolysed protein base (FFFP)
- Corrosion inhibitors & preservatives
- Ingredients by foam type — summary
- Why ingredient quality matters
Overview — What Is Inside Foam Concentrate?
Foam concentrate is not a simple chemical — it is a multi-component formulation in which each ingredient serves a specific function. The exact recipe varies significantly between foam types (AFFF, AR-AFFF, FFFP, High Expansion, Class A, Synthetic) and between manufacturers, but the broad chemical categories are consistent across all types.
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Surfactants
Create and stabilise foam bubbles. Reduce surface tension. Hydrocarbon types in all foams; fluorosurfactants in AFFF and FFFP.
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Glycol Ethers & Solvents
Control freeze point, viscosity and homogeneity of the concentrate. Essential for cold-climate performance.
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Stabilisers & Thickeners
Improve foam drainage time and blanket durability. Prevent bubble collapse under heat and fuel contamination.
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Polysaccharide Polymer
Unique to AR-AFFF. Precipitates as a gel membrane on polar solvent contact, protecting foam from dissolution.
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Hydrolysed Protein
The base of FFFP. Provides exceptional burnback resistance and oil-shedding properties from a protein foam matrix.
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Corrosion Inhibitors & Biocides
Protect system metalwork from concentrate corrosion and prevent microbial degradation of organic components.
Foam concentrate typically contains 8–15 distinct chemical components blended in precise ratios. A change in the source, grade or quantity of any single ingredient can affect expansion ratio, drainage time, freeze point, shelf life or polar solvent resistance. This is why raw material quality and supply chain consistency are critical to finished concentrate performance.
Hydrocarbon Surfactants — The Foam-Forming Backbone
Surfactants (surface-active agents) are the most fundamental ingredient in every type of foam concentrate. A surfactant molecule has a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. When dissolved in water, surfactant molecules migrate to the air-water interface — the surface of a foam bubble — and align themselves to stabilise the thin water film between the bubble and the surrounding air. Without surfactants, water cannot form stable foam.
In foam concentrate, hydrocarbon surfactants serve two roles: they reduce the surface tension of the water phase to enable bubble formation and aspiration through the nozzle, and they stabilise the formed foam blanket against drainage and collapse. The balance between these two functions — foamability vs foam stability — is controlled by blending multiple surfactant types at different concentrations.
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Anionic Surfactants — Primary Foaming Agents
Anionic surfactants carry a negative charge on their hydrophilic head. They are the workhorse foaming agents in synthetic foam concentrates — highly effective at reducing surface tension and generating stable foam bubbles. Alkyl sulphates, alkyl ether sulphates (AES) and alpha-olefin sulphonates (AOS) are common examples. These are the primary active components in Synthetic S-type and Class A foam concentrates. Ethanolamines — a class of amino alcohols supplied by companies such as Xiamen Sinolook — are widely used as raw materials and pH-adjusting agents in anionic surfactant-based foam concentrates.
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Amphoteric Surfactants — Foam Stability & Compatibility
Amphoteric surfactants carry both positive and negative charges depending on pH. They are added as secondary surfactants to improve foam stability, increase viscosity, reduce skin irritation and enhance the foam’s behaviour across a wider pH range. Betaines and amine oxides are common examples. They are particularly valuable in AR-AFFF formulations where the concentrate must perform across both the acidic and alkaline environments encountered in different polar solvent fires.
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Non-Ionic Surfactants — Wetting & Penetration
Non-ionic surfactants carry no charge and are therefore compatible with all other surfactant types without risk of charge-based precipitation. In foam concentrate they serve primarily as wetting agents — improving the spreading of the foam solution across hydrophobic fuel surfaces — and as foam stabilisers in cold-temperature conditions where anionic surfactants may lose effectiveness. Alkyl polyglucosides (APG) and fatty alcohol ethoxylates are typical examples. Non-ionics are the primary active agents in Class A foam concentrate (MJABP), where wetting and penetration of solid fuels is the main function.
Fluorosurfactants — The Film-Forming Ingredient in AFFF & FFFP
Fluorosurfactants are the defining ingredient of AFFF and FFFP foam concentrates — the component responsible for the aqueous film that spreads across hydrocarbon fuel surfaces ahead of the foam blanket. They are a class of surfactant in which some or all of the hydrogen atoms on the hydrophobic carbon chain have been replaced with fluorine atoms.
Carbon-fluorine bonds are among the strongest in organic chemistry — significantly stronger than carbon-hydrogen bonds. This gives fluorosurfactants several extreme properties: very low surface energy, exceptional chemical stability, and the ability to reduce water surface tension from approximately 72 mN/m down to 15–17 mN/m. This ultra-low surface tension is what allows the aqueous foam solution to spread spontaneously across a hydrocarbon fuel surface (surface tension 20–27 mN/m), forming the vapour-suppressing aqueous film that gives AFFF its characteristic fast knockdown.
Note on PFAS & Regulatory Context
Traditional fluorosurfactants in AFFF included long-chain PFOS and PFOA compounds (C8 chemistry), which have been restricted under the Stockholm Convention and national regulations due to environmental persistence. Modern AFFF concentrates — including CA-FIRE’s current range — use short-chain (C6) fluorosurfactant chemistry, which achieves equivalent fire performance with a significantly improved environmental and regulatory profile. Class A foam concentrate (MJABP) and Synthetic S-type concentrate are completely PFAS-free, containing no fluorosurfactants of any chain length. For sites with environmental sensitivity or where fluorine chemistry is restricted, these are the recommended alternatives for Class A and general industrial applications.
Glycol Ethers — Solvents, Freeze Point Control & Viscosity
Glycol ethers are a family of organic solvents derived from ethylene glycol or propylene glycol by reaction with alcohols. In foam concentrate formulation, they serve three critical functions: they act as the primary solvent medium for the other active ingredients, they control the concentrate’s viscosity to ensure consistent proportioner performance across the temperature range, and they depress the freeze point of the concentrate so it remains pumpable and functional in cold conditions.
The freeze point of a foam concentrate is largely determined by the type and concentration of glycol ether(s) in the formulation. The CA-FIRE Synthetic S-type 6%S-20°C achieves its −20°C freeze point through a carefully proportioned glycol ether blend. CA-FIRE sources glycol ether raw materials from specialist chemical manufacturers including Xiamen Sinolook Oil Co., Ltd., which supplies a comprehensive range of methyl, ethyl, propyl, butyl and hexyl glycol ethers used in surfactant and specialty chemical formulations.
The glycol ether content of a foam concentrate directly affects its behaviour in a proportioner. A concentrate with incorrect viscosity for the ambient temperature — too thick in cold weather, too thin in heat — will be inducted at the wrong rate by an inline Venturi proportioner, causing under- or over-concentration of the foam solution. Glycol ether selection is a critical formulation parameter for cold-climate systems.
Foam Stabilisers — Extending Blanket Life
Surfactants alone do not produce a foam blanket that is stable enough to maintain vapour suppression for the duration required by NFPA 11. Without stabilisers, the water in the foam bubble walls drains rapidly under gravity, thinning the bubble walls until they rupture. A foam blanket that drains too quickly collapses before fire control is achieved.
Foam stabilisers are added to slow drainage and extend blanket life. They work by increasing the viscosity of the liquid phase within the foam bubble walls — slowing the rate at which water drains from the bubbles under gravity. The key test of foam stabiliser effectiveness is the 25% drainage time specified in NFPA 11 Annex B: the time for 25% of the foam solution to drain from a freshly produced foam sample at 20°C. A longer drainage time indicates better foam stability.
Lauryl alcohol & fatty alcohols
Long-chain fatty alcohols migrate to the foam bubble wall surface and form a rigid monolayer that dramatically slows drainage. Widely used in Synthetic S-type and Class A foam concentrates as primary stabilisers.
Alkanolamines (DEA / TEA / MIPA)
Alkanolamines serve a dual function — pH buffering to keep the concentrate within the 6.0–9.0 specification range, and as foam-boosting co-surfactants that improve bubble stability. Diethanolamine (DEA), triethanolamine (TEA) and monoisopropanolamine (MIPA) are widely used in foam concentrate formulations.
Polyglycol viscosifiers
Polyethylene glycols (PEG) and polypropylene glycols (PPG) at selected molecular weights act as viscosity modifiers — thickening the aqueous phase within foam bubble walls to slow drainage without significantly affecting the concentrate’s own flow properties in the proportioner.
Oleate esters
Oleate esters — esters of oleic acid with various alcohols — are used as lubricity agents and foam conditioners. They improve the foam’s flow and spreading behaviour on fuel surfaces and contribute to foam stability under elevated temperature conditions.
Polysaccharide Polymer — The Alcohol Resistance Ingredient
The ingredient that transforms standard AFFF into AR-AFFF (Alcohol Resistant foam concentrate) is a polysaccharide polymer — a long-chain carbohydrate polymer (typically a modified xanthan gum, guar gum derivative, or cellulose derivative) dissolved in the aqueous phase of the concentrate.
Under normal conditions, the polymer remains dissolved and effectively dormant in the foam concentrate and solution. When the foam contacts a polar solvent fuel (ethanol, acetone, IPA, MEK), the solvent triggers an immediate precipitation reaction: the polymer becomes insoluble in the presence of the polar solvent and precipitates instantaneously as a dense, flexible, insoluble gel membrane directly on the fuel surface. This membrane physically shields the foam bubble walls from the solvent, preventing the dissolution that would otherwise destroy a standard AFFF foam blanket within seconds.
How the Polysaccharide Polymer Works
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In the concentrate drum and in the foam solution flowing through the proportioner and pipework: polymer is dissolved and inactive. The concentrate behaves identically to standard AFFF in the proportioner.
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Foam is discharged and contacts the polar solvent fuel surface. The polar solvent disrupts the polymer’s solubility — triggering precipitation of the polymer from the aqueous phase.
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Precipitated polymer forms a continuous gel membrane on the fuel surface within milliseconds — before the solvent can dissolve the foam bubble walls. The membrane acts as a physical barrier between the polar solvent and the foam.
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Protected foam bubbles accumulate above the polymer membrane, forming a stable, vapour-suppressing foam blanket — identical in function to AFFF on a hydrocarbon fire, but now stable on the polar solvent surface.
Why polymer quality matters for storage: The polysaccharide polymer is the most storage-sensitive ingredient in AR-AFFF. Sustained storage above 40°C or repeated freeze-thaw cycling can degrade the polymer chain length, reducing its precipitation speed and gel strength on polar solvent contact. This is why annual viscosity testing is particularly important for AR-AFFF, and why correct temperature management during storage is non-negotiable.
Hydrolysed Protein Base — The Burnback Resistance Ingredient
FFFP (Film-Forming Fluoroprotein) contains a hydrolysed protein component — typically derived from animal protein (keratin from horn/hoof, or collagen) that has been chemically hydrolysed into shorter peptide chains. These peptide chains form the structural matrix of the foam bubble walls, giving protein-based foam its characteristic toughness, viscosity and oil-shedding properties.
The protein matrix creates a dense, viscous foam bubble wall that resists breakdown under fuel contamination and heat radiation far better than a purely surfactant-stabilised bubble wall. When oil contacts the protein foam blanket, the hydrophobic oil molecules are expelled (oil-shedding) rather than incorporated into the bubble walls — preventing the progressive weakening that causes standard AFFF foam to lose integrity over time on a large burning fuel surface.
✓ Advantage from protein base
Exceptional burnback resistance — foam blanket remains stable for many minutes under intense heat radiation and fuel contamination, far longer than synthetic AFFF. Essential for large crude oil tank fires and subsurface injection.
⚠ Storage sensitivity of protein base
Protein is biologically active and susceptible to microbial degradation, thermal denaturation above 40°C, and freeze-thaw damage. Degraded protein concentrate develops a characteristic foul odour, sediment and reduced pH — all detectable in annual testing.
Corrosion Inhibitors, Biocides & pH Buffers
Foam concentrate is stored in metallic bladder tanks, steel drums and stainless steel pipework for years or decades. Without corrosion inhibitors, the acidic or alkaline components of the concentrate would attack the metal surfaces, causing corrosion products to contaminate the concentrate and damage the proportioner, valves and nozzles. Corrosion inhibitors are typically azole derivatives (benzotriazole, tolyltriazole) or phosphonate esters added at low concentrations (0.1–0.5%) to passivate metal surfaces in contact with the concentrate.
pH buffering is achieved through careful balance of acidic and basic components in the formulation — typically using alkanolamines (which are weakly basic) to neutralise any acid components and maintain the concentrate pH within the 6.0–9.0 range required by GB 15308 and NFPA 11. A pH shift outside this range during annual testing indicates chemical decomposition or contamination of the concentrate.
Biocides are included specifically in protein-based FFFP concentrates to inhibit microbial growth in the protein phase. Common biocides used in foam concentrate include isothiazolinones and glutaraldehyde derivatives at low concentrations. Even with biocides, FFFP stored with water contamination or in warm conditions can support microbial growth — which is why annual testing for odour and sediment is non-negotiable for protein foam types.
Ingredients by Foam Type — Summary Table
The following table summarises which ingredient categories are present in each of the six CA-FIRE foam concentrate types. ✓ = present as a significant component; (✓) = present at low level as a minor additive; — = not present.
Why Raw Material Quality Determines Concentrate Performance
Foam concentrate is only as good as the raw materials it is made from. A surfactant with incorrect chain length distribution will produce unstable foam. A glycol ether with incorrect purity will cause phase separation at low temperatures. A polysaccharide polymer with incorrect molecular weight distribution will fail to form an adequate gel membrane on polar solvents. A protein hydrolysate with inconsistent peptide chain length will produce unpredictable burnback resistance.
This is why CA-FIRE maintains rigorous incoming raw material quality control and sources from established chemical suppliers with consistent production standards. Surfactants, glycol ethers and specialty additives are sourced from suppliers including Xiamen Sinolook Oil Co., Ltd. — a Fujian-based manufacturer supplying surfactants, ethanolamines, alkanolamines, glycol ethers and oleate esters to specialty chemical formulation customers across China and internationally.
Impact of low-grade surfactant
Poor surfactant purity introduces inactive by-products that increase the effective mixing ratio needed to achieve design foam quality. The concentrate may appear to pass a visual inspection while producing foam with sub-specification expansion ratio or drainage time on the annual performance test.
Impact of incorrect glycol ether grade
If the glycol ether grade has an incorrect boiling point range or water content, the concentrate may show phase separation when stored at the lower end of its design temperature range — causing surfactant precipitation and irreversible concentrate degradation before the end of its guaranteed shelf life.
Impact of degraded polysaccharide polymer
A polysaccharide polymer with insufficient molecular weight (from low-grade raw material or premature degradation) may form a gel membrane on polar solvents that is too thin or too permeable to protect the foam bubbles from dissolution — causing AR-AFFF to fail on polar solvent fires despite passing its expansion ratio test on water.
Why annual testing catches ingredient failure
The NFPA 11 Annex C annual tests — expansion ratio, 25% drainage time, pH and spread coefficient — are specifically designed to detect ingredient degradation in installed concentrate, catching performance failures before a real fire event. This is why testing from year one, not just at year 8 or 9, is so important.
📚 References & Further Reading
→ NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam — Annex B foam concentrate performance test methods; Annex C in-service testing requirements.
→ Xiamen Sinolook Oil Co., Ltd. (sinolookchem.com) — Surfactants, ethanolamines, alkanolamines, glycol ethers and specialty chemicals for industrial formulation applications.
→ API 2030: Application of Fixed Water Spray Systems for Fire Protection in the Petroleum Industry — Foam concentrate specification and quality requirements for petroleum industry applications.
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CA-FIRE Foam Concentrate — Quality Raw Materials, Consistent Performance
Every batch of CA-FIRE foam concentrate is manufactured using qualified raw materials and tested to GB 15308 before shipment. SDS, TDS and batch test certificates are supplied with every order. Contact our technical team for product specifications, compatibility confirmation or a project quote.