Choosing the wrong type of firefighting foam concentrate can mean the difference between rapid suppression and a foam that collapses within seconds of touching the fuel. With six distinct foam concentrate types on the market — each engineered for a specific set of hazards and system designs — selecting the right agent is one of the most consequential decisions in fire system specification.
This guide covers all six types in the CA-FIRE foam concentrate range: AFFF, AR-AFFF, FFFP, High Expansion, Class A and Synthetic S-type. For each type we explain the suppression mechanism, fire class suitability, key technical parameters and the scenarios where it performs best — so you can make an informed choice for your project.
In This Article
Low expansion · Surface applied
201–1000× · Oxygen displacement
CAFS compatible
Class B · Hydrocarbon Fuels
AFFF — Aqueous Film Forming Foam Concentrate
AFFF (Aqueous Film Forming Foam) is the most widely specified foam concentrate for Class B hydrocarbon fuel fires. It owes its rapid knockdown performance to fluorosurfactants that cause a thin, self-spreading aqueous film to form on the hydrocarbon fuel surface — ahead of the advancing foam blanket. This film suppresses flammable vapour almost instantly, achieving fire control faster than any other foam type on petroleum fuels.
According to NFPA 11 (Standard for Low-, Medium-, and High-Expansion Foam), AFFF is the standard agent for fixed foam systems on petroleum storage tanks, airport rescue and firefighting (ARFF), and fuel loading terminals. It is available in 3% (model S-3-AB) and 6% (S-6-AB) mixing ratios — the percentage refers to the volume of concentrate in the final foam solution.
Key limitation: Standard AFFF is not effective on polar solvent fires (alcohols, ketones, esters). If your site handles both petroleum products and water-miscible solvents, specify AR-AFFF instead.
Class B · Hydrocarbons & Polar Solvents
AR-AFFF — Alcohol Resistant Foam Concentrate
AR-AFFF (Alcohol Resistant Aqueous Film Forming Foam) is the correct agent whenever polar solvents — ethanol, methanol, IPA, acetone, MEK and similar water-miscible flammable liquids — are part of the fire hazard. Standard AFFF fails on these fuels because the polar solvent immediately dissolves the foam bubble walls, causing rapid foam collapse before any meaningful vapour suppression occurs.
AR-AFFF solves this through a polysaccharide polymer additive. When the foam contacts a polar solvent, the polymer precipitates instantly as an insoluble gel membrane on the fuel surface — physically shielding the foam from dissolution. The result is a stable foam blanket on polar solvents that would destroy standard AFFF within seconds.
CA-FIRE offers two AR-AFFF formulation types: AFFF/AR (fluoroprotein-based, retains aqueous film formation) and S/AR (purely synthetic, preferred where non-protein chemistry is specified). Both are available in 3×3% and 6×6% ratios, with sea water grades (freeze point −36°C) for marine installations. The notation “3×3%” means 3% on hydrocarbon fuels and 3% on polar solvents — one ratio covers both fuel types.
Polar solvent dissolves foam walls → foam collapses in seconds → no vapour suppression → fire continues.
Polymer membrane shields foam from fuel → stable blanket forms → vapour suppressed → fire controlled.
Class B · Large Oil Tank Fires
FFFP — Film-Forming Fluoroprotein Foam Concentrate
FFFP (Film-Forming Fluoroprotein) occupies a unique position in the foam concentrate range — it is the only type that combines the rapid aqueous-film knockdown of AFFF with the superior burnback resistance and oil-shedding durability of protein-based foam. This dual-action performance makes FFFP the preferred agent for large petroleum storage tank fires, where both fast initial suppression and sustained foam blanket integrity over a prolonged suppression operation are required.
Burnback resistance — the foam’s ability to resist re-ignition after initial knockdown — is the defining advantage of FFFP over standard AFFF. On a large crude oil tank, the foam blanket must remain stable for many minutes while firefighters approach, cool the tank shell and eliminate ignition sources. AFFF foam degrades relatively quickly under fuel contamination and heat radiation. FFFP’s protein matrix creates a dense, viscous, oil-shedding blanket that resists breakdown far longer.
FFFP is also the preferred agent for subsurface injection systems — where foam solution is pumped through a base pipe and must rise through the full fuel column before reaching the burning surface. The fluoroprotein base sheds oil from the foam bubble walls during ascent, arriving at the surface with far better integrity than standard AFFF.
Quick Comparison: AFFF vs Fluoroprotein vs FFFP
| Property | AFFF | Fluoroprotein | FFFP ✦ |
|---|---|---|---|
| Initial knockdown speed | Excellent | Good | Excellent |
| Burnback resistance | Limited | Excellent | Excellent |
| Subsurface injection | Poor | Good | Good |
| Aqueous film formation | Yes | No | Yes |
Enclosed Spaces · Oxygen Displacement
High Expansion Foam Concentrate — YEG-3 & YEG-6
High expansion foam concentrate is in a different category from all other foam types. Rather than forming a surface blanket on burning fuel, it completely floods an enclosed space with foam — displacing oxygen below the level needed to sustain combustion (approximately 15%) and simultaneously cooling the burning material. CA-FIRE’s YEG-3 (3%) and YEG-6 (6%) produce an expansion ratio of 201 to 1000 times the liquid volume when passed through a high-expansion foam generator.
This extreme expansion ratio means 1 litre of foam solution can produce up to 1,000 litres of finished foam — enough to flood a 500 m³ ship engine room using just 0.5 m³ of foam solution at 1000× expansion. No other suppression technology can protect a fully enclosed space so efficiently with so little water.
High expansion foam is mandated by NFPA 11 for specific enclosed-space applications including ship engine rooms (2-minute fill time requirement) and aircraft hangars (NFPA 409 Group I and II, minimum 600 mm foam depth within 4 minutes). It requires a dedicated high-expansion foam generator — standard foam branches and monitors cannot produce high expansion foam.
Expansion Ratio Comparison
→ View High Expansion Foam Concentrate — YEG-3 & YEG-6, NFPA 11 data & quote
Class A · Wildland & Structural · CAFS
Class A Foam Concentrate — MJABP
Class A foam concentrate is not really a “foam” in the same sense as AFFF or FFFP — it is a surfactant-based wetting agent that transforms ordinary water into a far more effective firefighting medium for solid fuel fires. When added to water at just 0.1–1%, it reduces the surface tension of water from approximately 72 mN/m to 15–20 mN/m — enabling the treated water to spread instantly across fuel surfaces and wick deep into porous solid fuels by capillary action, rather than beading up and running off.
Research by the USDA Forest Service has consistently demonstrated that Class A foam can reduce the water needed to achieve equivalent fuel cooling and knockdown by 50–75% compared to plain water — a critical advantage on aerial tankers and fire engines where water supply is finite.
CA-FIRE MJABP is the standard agent for CAFS (Compressed Air Foam Systems), which inject compressed air into the foam solution before the hose to produce a dry, lightweight foam that clings to vertical surfaces and can be projected over long distances. It contains no fluorosurfactants or PFAS compounds — safe for use in wildland environments.
Important: Class A foam is NOT effective on Class B flammable liquid fires — it does not form a vapour-suppressing foam blanket on liquid fuel surfaces. For sites with both hazard classes, specify Synthetic S-type foam (covers both A and B) or maintain two separate foam systems.
→ View Class A Foam Concentrate MJABP — CAFS data, SDS & quote
Class A & B · General Purpose · CAFS
Synthetic Foam Concentrate — S-Type
Synthetic foam concentrate S-type is the most versatile agent in the range — a hydrocarbon-surfactant-based foam that covers both Class A and Class B fires from a single product stock. It is the go-to choice for general industrial fire protection where both solid fuel and liquid fuel hazards are present and maintaining two separate foam agents would add unnecessary cost and operational complexity.
CA-FIRE S-type is available in 3%S-8°C (3% ratio, freeze point −8°C) and 6%S-20°C (6% ratio, freeze point −20°C). The 6% model’s lower freeze point makes it the preferred choice for cold-climate outdoor tank systems and offshore installations. Compared to protein-based foams (FFFP), S-type offers a significantly longer shelf life, no protein degradation or odour issues, and lower viscosity for reliable cold-temperature proportioner flow.
Limitation: Standard S-type synthetic foam is NOT effective on polar solvent fires (alcohols, ketones, esters). For sites with alcohol or solvent hazards, specify AR-AFFF.
→ View Synthetic Foam Concentrate S-Type — SDS, cold-climate data & quote
All 6 Foam Concentrate Types — Full Comparison
Use this table to narrow down the correct agent for your fire hazard and system design.
How to Choose the Right Foam Concentrate Type
Use this decision framework to match the foam type to your hazard scenario. Always consult your system designer and verify the agent specification meets the applicable standard (NFPA 11, GB 15308 or local equivalent) for your installation.
Yes → Specify AR-AFFF. Standard AFFF and S-type will fail on these fuels. AR-AFFF covers both polar solvents and hydrocarbons from a single stock.
Yes → Specify FFFP for superior burnback resistance. AFFF is acceptable for smaller tanks where re-ignition risk during the suppression operation is lower.
Yes → Specify High Expansion Foam. Only high expansion foam can flood an enclosed space to suppress a fire by oxygen displacement. AFFF and FFFP are for surface-applied open-area systems.
Yes → Specify Class A Foam MJABP for pure Class A scenarios. It is the most water-efficient and concentrate-efficient option at 0.1–1% ratio. PFAS-free, CAFS-optimised.
Yes → Specify Synthetic S-Type (3%S-8°C for temperate, 6%S-20°C for cold climates). Simplest procurement — one product covers both hazard classes.
📚 Industry Standards & Further Reading
- 🔗 NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam (NFPA.org)
- 🔗 NFPA 409: Standard on Aircraft Hangars — Foam System Requirements (NFPA.org)
- 🔗 API 2030: Application of Fixed Water Spray Systems for Fire Protection in the Petroleum Industry (API.org)
- 🔗 USDA Forest Service: Class A Foam for Wildland Fire Suppression (fs.usda.gov)
Need Help Choosing the Right Foam Concentrate?
CA-FIRE’s technical team can advise on agent selection, mixing ratio, system compatibility and NFPA 11 documentation for your project. Factory direct pricing on all 6 foam types.