Operation of fire fighting foam proportioner / foam inductor / eductor

Fonctionnement des injecteurs proportionneurs dans la lutte incendie

What is a FIREFIGHTING foam proportioner?


The foam proportioner is a firefighting equipment used by firefighters in the context of firefighting. It is used to dose the foam concentrate in proportion to the flow of water, in order to form foam to extinguish fires. It is also called an "foam inductor", “foam eductor”, “foam generator” or "foam dosing system".

The firefighting foam proportioner is placed between the water inlet and the foam discharge device (firefighting foam nozzle or firefighting monitor). Depending on its use, it can be fixed onto a fire vehicle, or portable. Various connections are possible (BSP, Storz, DSP, GFR, etc.).

Foam_proportioner_foam_dosing_system_foam_generator_foam_inductor_firefighting_equipmentThe principle of the foam inductor / eductor is to mix the pressurized water and the foam concentrate, to form a “premix solution” (concentration). This premix will then be charged with air in the foam discharge device (expansion).

The foaming agent (wetting-foaming additive or foam concentrate, synthetic or protein) is sucked by a hose with a plunger rod from its container (pail, drum or tote).
By varying the proportions of water, foam concentrate and air, foams of different consistencies are obtained, intended for specific applications.


How does a FIREFIGHTING foam proportioner work?



  • Foam proportioners with venturi principle:

In a venturi foam proportioner, pressurized water passes through the converging and then diverging cones. Passing through the convergent will accelerate the flow rate and create a vacuum which causes the foam concentrate to be drawn in (by suction). The divergent then makes it possible to return to fluid normal speed at the foam dosing system outlet. The in-line venturi-type foam proportioner can be fixed-flow or automatic flow (automatically adapts to fluctuating water flow, example of the LEADERMIX foam proportioner).

LEADER fixed-flow venturi eductor system LEADER MIX automatic venturi foam proportioner





Discover how the LEADER MIX firefighting foam proportioner / foam inductor / foam eductor works in video



  • Water-driven pump foam dosing system:

    Injector operating in proportion to the flow of water, thanks to a water turbine that drives a piston pump, or a rotary pump, which sucks the foam concentrate.


  • Electronic foam generator:

    Electronic system, powered by the current of the fire vehicle, which calculates the water flow and controls an electric pump which will then inject the requested quantity of foam concentrate.


  • Around the pump foam proportioner:

    What is an around the pump proportioner ?
    Based on the venturi principle, this foam inductor / eductor is placed in parallel around the fire vehicle pump. The foam concentrate will thus be injected upstream of the pump.

FLOWMIX, foam dosing unit
  • Foam Storage and foam dosing system :
    A pressure tap on the water inlet is taken upstream of the foam dosing unit, this pressure will crush a bladder filled with foam concentrate. The foam concentrate will therefore be forced out of the bladder under pressure and injected into the water stream to obtain a premix. The FLOWMIX foam dosing unit works on this principle. 


Foam inductors / eductors can be fixed flow or variable flow.

The flow rate corresponds to the quantity of water that will pass through the foam proportioner over a specific period of time. This quantity of water may vary depending on the pressure, the pumping equipment used, and the type of discharge devices (nozzle, monitor, foam generator, foam pourer, etc.).

  • For fixed flow foam proportioners: the foam inductor will dose a precise quantity of foam concentrate according to a fixed water flow rate, at 200l/min for example.
  • For variable flow foam proportioners: the mixing proportional valve operates and adapts the injection according to a flow rate range defined by the manufacturer. For example, LEADER MIX AB 2000 foam proportioner will inject the required amount of firefighting foam concentrate over a flow rate range from 300 to 2000l/min.


Foam proportioners can be calibrated for a fixed concentration or several adjustable concentrations.

The concentration is the % of foam concentrate mixed with water to obtain finished foam. In general, the foam concentrate is formulated to be effective at a specific concentration level depending on the type of fire. For example: ECOPOL 3 foam concentrate can be used at a concentration rate of 3% on hydrocarbon fires and 3% on polar solvent fires.

Firefighters are using a 3% foam concentrate with a foam proportioner 

  • In the case of a fixed concentration foam proportioner, the inductor is calibrated to inject a certain percentage of foam concentrate. For example, a foam proportioner calibrated at 6% will mix 6 liters of foam concentrate with 94 liters of water to make 100 liters of premix solution.
  • For foam proportioners with adjustable concentration rate, different concentration rates are calibrated. They generally vary between 0.1% and 6%. Depending on the model, the concentration rate can be adjusted manually via a selector, or electronically on a control panel.

The firefighting equipment manufacturer LEADER offers autonomous foam proportioners (or also called foam inductors / foam eductors or foam generator) based on venturi injection or storage unit principle. They automatically adapt to flow variations and with the possibility to choose the foam concentration rate. Practical, compact and economical solutions!

To find out more, discover the LEADER range of firefightng foam proportioners!

LEADER also offers other firefighting equipment such as mobile foam generator and high expansion foam generator for fixed installation.

Discover our other expertises on firefighting foam generator (firefighting proportioners, firefighting foam eductor/inductor).

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