Quick Answer
Foam concentrate is the undiluted liquid product you purchase and store. Foam solution is what you get when you mix the concentrate with water at the correct ratio (3% or 6%). Finished foam is what comes out of the nozzle after the solution is aspirated with air. You buy concentrate. The system makes solution. The nozzle makes foam.
If you have just started specifying, purchasing or managing a foam fire suppression system, the terminology can be confusing. “Foam concentrate,” “foam solution,” “foam,” “expansion ratio,” “mixing ratio,” “proportioner” — these terms are often used loosely in supplier catalogues and maintenance documents, and the distinctions between them genuinely matter when you are ordering the right product, calibrating a proportioner, or interpreting an inspection report.
This guide defines each term precisely, explains how they relate to each other, and walks through the complete chain from concentrate drum to finished foam on a fire — so you can buy, install and maintain your foam system with confidence.
Contents
The Three Things: Concentrate, Solution and Foam
The entire process of foam fire suppression involves three distinct substances — concentrate, solution and finished foam — each at a different stage of the system. Understanding the difference between them is the foundation of every other concept in foam fire protection.
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CONCENTRATE
The undiluted product in the drum, IBC or bladder tank. What you buy and store. Typically 3% or 6% mixing ratio.
+ WATER
→
via proportioner
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SOLUTION
Concentrate mixed with water. Flows through the system pipework. Not yet foam — it is a liquid.
+ AIR
→
via nozzle / generator
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FOAM
Solution aspirated with air. The finished product applied to the fire. 6× to 1000× the solution volume.
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The simple rule: You purchase and store concentrate. Your proportioner makes solution. Your nozzle or generator makes foam. When someone asks “how much foam do you have?” the technically correct answer is based on how much concentrate is in storage — because the system makes the rest from your water supply on demand.
What Is Foam Concentrate?
Foam concentrate is the undiluted, active-agent liquid product that forms the basis of firefighting foam. It is a precisely formulated mixture of surfactants (surface-active agents), stabilisers, solvents, and — depending on the type — polymers, fluorosurfactants or protein hydrolysates. On its own, concentrate does nothing to fight a fire. It must first be diluted with water to make foam solution, then aspirated with air to produce finished foam.
Concentrate is what you see in the supplier catalogue, what you order by the drum or IBC, what you store in your bladder tank or concentrate storage tank, and what your system’s proportioner meters into the water supply. It is the valuable, active component — the rest (water and air) comes from your facility’s existing supplies.
What Is Foam Solution?
Foam solution is the mixture of foam concentrate and water produced by the proportioning system. It is a homogeneous liquid — not yet foam — that flows through the system pipework from the proportioner to the foam-generating nozzle or generator. When foam solution reaches the nozzle, air is entrained (aspirated) into it to produce the finished foam.
The composition of foam solution is defined by the mixing ratio. A 3% foam solution contains 3 parts concentrate and 97 parts water per 100 parts total. A 6% foam solution contains 6 parts concentrate and 94 parts water. The solution is still a liquid at this stage — the colour and appearance will vary by foam type, but it has no fire-suppression capability until it is aerated into foam at the nozzle.
Foam Solution Composition by Mixing Ratio
3% Foam Solution
per 100 L total
per 100 L total
3 L concentrate
97 L water
6% Foam Solution
per 100 L total
per 100 L total
6 L concentrate
94 L water
Important: Foam solution cannot be pre-mixed and stored for later use. Once concentrate is mixed with water it begins to degrade — the surfactant balance shifts, foam stability reduces, and the solution becomes less effective over time. Always proportion fresh solution from concentrate at the point of use.
What Is Finished Foam?
Finished foam — or simply “foam” — is what exits the nozzle or foam generator and is applied to the fire. It is produced by aspirating (entraining) air into the foam solution. The surfactants in the concentrate stabilise the air bubbles, producing a persistent foam blanket rather than unstable froth that collapses immediately.
The volume of foam produced from a given volume of solution is defined by the expansion ratio. A low-expansion foam (6–9×) produces 6 to 9 litres of foam from every litre of solution. A high-expansion foam (201–1000×) produces up to 1000 litres of foam from a single litre of solution. The expansion ratio determines how the foam behaves — low expansion forms a dense, fuel-surface-sealing blanket; high expansion floods enclosed spaces by volume.
Low Expansion Foam
6–9×
Dense, wet foam blanket. Seals fuel surface, suppresses vapour, cools fuel. Applied through standard foam branches and monitors. Used for AFFF, AR-AFFF, FFFP and Synthetic S-type.
Typical use: Petroleum tanks, fuel spill fires, airport ARFF, marine
High Expansion Foam
201–1000×
Light, dry foam mass that fills enclosed spaces. Displaces oxygen for smothering suppression. Requires a high-expansion foam generator (blower type). Used for YEG-3 and YEG-6 concentrate.
Typical use: Engine rooms, aircraft hangars, mines, underground car parks
Mixing Ratio Explained
The mixing ratio is the percentage of foam concentrate in the foam solution. A 3% mixing ratio means 3 parts concentrate plus 97 parts water. A 6% mixing ratio means 6 parts concentrate plus 94 parts water. The mixing ratio is the most important number on a foam concentrate product specification — it determines everything from how much concentrate you need to buy and store, to how your proportioner must be calibrated.
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3% and 6% produce identical fire performance when correctly proportioned. The percentage does not indicate strength or quality — it is simply the concentration in the solution. See our guide: AFFF 3% vs 6% — which mixing ratio do you need?
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The mixing ratio must match your proportioner calibration. Your proportioner is a fixed-ratio device — it is designed to induct either 3% or 6% of concentrate into the water flow. Using 3% concentrate in a 6%-calibrated proportioner will under-concentrate your solution; using 6% in a 3%-calibrated system will over-concentrate it. Both reduce fire performance and breach NFPA 11 compliance.
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AR-AFFF uses a double-percentage notation — for example, 3×3% — meaning the same 3% ratio is applied to both hydrocarbon fuels and polar solvent fuels. This simplifies operation by eliminating the need to adjust the proportioner between fuel types.
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Class A foam concentrate uses a much lower ratio — typically 0.1% to 1% — because it is a wetting agent, not a film-forming or smothering agent. Even at 0.1%, it significantly changes the surface tension of the water to enable deep penetration into solid fuels.
Expansion Ratio Explained
The expansion ratio is the volume of finished foam produced divided by the volume of foam solution used. It is determined by how much air is entrained into the solution at the nozzle or generator — not by the concentrate type or mixing ratio. A 3% solution and a 6% solution made from the same concentrate type will produce the same expansion ratio when passed through the same nozzle.
Note: Do not confuse the mixing ratio (concentrate % in solution) with the expansion ratio (foam volume ÷ solution volume). They are completely separate parameters — a 3% mixing ratio concentrate can produce 6× expansion or 1000× expansion depending on the nozzle or generator used.
What Is Proportioning?
Proportioning is the process of mixing foam concentrate with water at the correct ratio to produce foam solution. The device that does this is called a proportioner. There are several types — each works differently but all achieve the same goal: introducing the correct percentage of concentrate into the water flow.
Inline / Venturi Proportioner
Uses the pressure differential (Venturi effect) created by water flowing through a restriction to draw concentrate from a tank. Simple, no moving parts, no power required. Most common for portable and semi-fixed systems.
Bladder Tank Proportioner
A pressure vessel with an internal rubber bladder separating concentrate from water. Water pressure compresses the bladder, pushing concentrate out and into the water stream at the design ratio. Reliable and accurate for fixed systems.
Balanced Pressure Pump Skid
A pump and metering valve system that delivers concentrate at the same pressure as the water supply, allowing accurate ratio control across a wide flow range. Used for large fixed systems, refineries and tank farms.
Around-the-Pump Proportioner
A bypass loop around the fire pump that uses the pressure differential across the pump to draw concentrate from a tank. Common on fire engines and mobile foam tenders where simplicity and reliability are paramount.
Key point: Every proportioner is calibrated for a specific mixing ratio — either 3% or 6% — at the time of manufacture. This calibration is fixed and cannot be changed by simply loading a different concentrate. The concentrate percentage must always match the proportioner calibration. Check the proportioner nameplate or original system drawing before ordering concentrate.
How Much Concentrate Do You Need to Order?
Once you know your mixing ratio and system flow rate, calculating the required concentrate volume is straightforward. Use this formula:
Concentrate Volume Formula
Concentrate (L) = Flow Rate (L/min) × Mixing Ratio (%) × Duration (min)
Add 10–15% safety margin to the calculated volume
Example A — Portable System
Flow rate: 200 L/min
Mixing ratio: 3%
Duration: 20 min (NFPA 11 minimum)
Mixing ratio: 3%
Duration: 20 min (NFPA 11 minimum)
Concentrate needed: 200 × 3% × 20 = 120 L
+ 15% margin = 138 L → order 140 L (7 × 20 L jerricans)
+ 15% margin = 138 L → order 140 L (7 × 20 L jerricans)
Example B — Fixed Tank System
Flow rate: 800 L/min
Mixing ratio: 6%
Duration: 30 min (large tank design)
Mixing ratio: 6%
Duration: 30 min (large tank design)
Concentrate needed: 800 × 6% × 30 = 1,440 L
+ 15% margin = 1,656 L → order 2 × 1,000 L IBCs
+ 15% margin = 1,656 L → order 2 × 1,000 L IBCs
If you are unsure of your system flow rate or design duration, check your fire protection drawing or contact your system installer. CA-FIRE’s technical team can also assist with concentrate sizing calculations — contact sales@ca-fire.com with your system details.
Common Terminology Mistakes — and Why They Matter
Mistake: Ordering “foam” when you mean “concentrate”
Suppliers sell concentrate, not finished foam. When you place an order, you specify the concentrate type (AFFF, AR-AFFF, etc.), mixing ratio (3% or 6%) and quantity in litres or drums. “Ordering foam” without these details is ambiguous — always use the specific product name and model number to avoid receiving the wrong product.
Mistake: Confusing mixing ratio with expansion ratio
These are completely different numbers. A 3% mixing ratio means 3% concentrate in the solution. A 6× expansion ratio means the foam volume is 6 times the solution volume. You can have a 3% concentrate that produces 6× expansion, or a 3% concentrate that produces 500× expansion — the expansion is controlled by the nozzle or generator, not the mixing ratio.
Mistake: Pre-mixing concentrate with water for storage
Foam solution degrades rapidly — particularly protein-based types — and cannot be stored for later use. Always store concentrate and water separately, letting the proportioner mix them at the point of use. Pre-mixed solution will fail its performance test and may promote microbial growth in the storage vessel.
Mistake: Assuming more concentrate = more effective foam
Over-concentrating the solution (using more concentrate than the design ratio) does not improve foam performance — it wastes concentrate and may actually reduce foam quality by altering the surfactant balance. Always proportion at exactly the specified ratio. 3% in a 3%-calibrated system is optimal; more is not better.
Mistake: Using any foam type on any fire class
Different foam types are formulated for specific fire classes. Standard AFFF on a polar solvent fire (ethanol, acetone) will fail instantly — the foam collapses on contact with the water-miscible fuel. Class A foam on a petroleum fuel fire provides no vapour suppression. Always match concentrate type to fire class — see our types of foam concentrate guide for the correct selection.
Which Foam Concentrate Do You Need?
Now you understand the terminology, use this quick selection guide to find the right concentrate for your application. Click through to each product page for full technical data, specifications and a quote.
AFFF
Class B hydrocarbon fires — petroleum, diesel, jet fuel, gasoline
Low expansion · 3% or 6% · Fresh & sea water · Fastest knockdown on hydrocarbons · Not suitable for polar solvents
AR-AFFF
Polar solvents (alcohols, ketones) AND hydrocarbons
Low expansion · 3×3% or 6×6% · Sea water grade available · AFFF/AR and S/AR types · Chemical plants, distilleries, mixed-fuel sites
FFFP
Large oil tanks, floating-roof tanks, subsurface injection
Low expansion · 3% or 6% · Best burnback resistance + aqueous film · Preferred for crude oil storage & ARFF twin-agent
Hi-Ex
Enclosed spaces — engine rooms, hangars, mines, car parks
201–1000× expansion · 3% or 6% · YEG-3 / YEG-6 · Oxygen displacement + cooling · Requires high-expansion generator
Class A
Wildland fires, structural fires, CAFS systems, solid fuels
0.1–1% mixing ratio · MJABP · PFAS-free · Wetting agent — deep fuel penetration · Not for Class B liquid fires
Synthetic
General industrial, mixed Class A & B hazards, cold climates
3% or 6% · 3%S-8°C / 6%S-20°C · CAFS compatible · Longest shelf life · Not for polar solvents
→ For a full side-by-side comparison: Types of Foam Concentrate — all 6 types compared
📚 Standards & Technical References
→ NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam — Definitions of foam concentrate, foam solution, expansion ratio and proportioning requirements (Chapter 3 and Chapter 4).
→ NFPA 16: Standard for the Installation of Foam-Water Sprinkler and Foam-Water Spray Systems — Proportioner types, installation requirements and mixing ratio verification testing.
→ API 2030: Application of Fixed Water Spray Systems for Fire Protection in the Petroleum Industry — Foam concentrate selection and proportioning guidance for petroleum storage facilities.
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Ready to Order the Right Foam Concentrate?
CA-FIRE manufactures all six foam concentrate types factory direct from Fujian. Tell us your foam type, mixing ratio, required quantity and proportioner type — we will confirm the correct product and provide pricing within one business day. SDS and GB 15308 test certificates supplied with every order.