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Foam extinguishing agent general features

What is fire extinguishing foam?

Extinguishing foam is composed of 3 ingredients: foam concentrate, water and air.

The foam concentrate is mixed with the water at its concentration of use, thus creating a foaming solution. Then, foaming solution is mixed with air to produce a highly fluid foam, which flows easily onto liquid surfaces (or to fill a volume). Foam is a stable bulk of air-filled bubbles with a lower density than oil, gasoline and water.


Concentration of use

This means the wished proportion of the foam concentrate in water.

A 6% emulsifier means that 6 parts of foam concentrate must be incorporated into 94 parts of water to obtain the foaming solution (for 100 liters of foaming solution, we will need 6 liters of foam concentrate).

Thus, a 3% foam concentrate is twice as concentrated as a 6% one since only 3 liters of foam concentrate is needed per 100 liters of foaming solution with an equivalent efficiency.

In addition, a foam concentrate is formulated to be effective at the nominal concentration. Underdosing necessarily leads to a loss of performance whereas an overdosing of foam concentrate will not necessarily improve efficiency (and will be a waste and a loss of operating life).

To go further, consult our wide range of dosing systems: linear proportioners (SFV ...), doser (VARIMIX ...).


Expansion ratio

The expansion ratio is the proportion between the volume of foam obtained and the volume of foaming solution used to produce this foam.

The expansion depends closely on the nature of the foam concentrate and the generator used.

Three kinds of expansion ratio have to be considered:

Low expansion

Usually used on surface fires (2D): for instance, hydrocarbons of large surfaces (storage tanks, retention basin). Due to its exceptional fluidity, the low expansion foam spreads over the entire surface of the fire in a very short time and is a real hermetic barrier. Moreover, because of its relatively high density, this foam can be projected, several tens of meters, via a monitor for instance. Low expansion foam is not sensitive to atmospheric condition (wind or rain). The foam is stable and provides resistant coverage. Its high water content also ensures a significant cooling. Depending on the foam concentrate and the monitor used, the low expansion foam adheres well to the vertical surfaces (=> thermal insulation).

Medium expansion

Used for small surfaces in enclosed (or partially enclosed) spaces (like solvents cell, cellars…). Thanks to its wide expansion range, these medium-expansion foams can be used for many applications. With an expansion from 50 to 100 times, for the protection of plastics, tires and liquids. For expansion from 100 to 200, the protection of “flooded” (and enclosed) areas where firefighting requires a rapid accumulation of large amounts of foam, eg canals, pits ... . The medium-expansion foam, due to its low density, is sensitive to wind.

High expansion

Thanks to its high expansion, large volumes such as hangars or storage sheds can be completely “flooded” with foam in a very short time. The high expansion foam is produced by foam generators.



To extinguish a fire the burning material must be separated from the atmospheric oxygen or cooled doawn to below the combustion temperature. This is exactly what fire extinguishing foam does.

The various extinguishing effects, which individually or together with others gaurantee a quick and sustainable extinguishing success react when using fire-extinguishing foam.

Separating effect

The closed foam cover separates the combustion zone from the ambient air and prevents any further supply of oxygen to the flammable material.

Cooling effect

It takes a lot of energy to turn liquid water into water vapour. The cooling effect uses this principle to extinguish fires. Indeed, the water contained in the foam evaporates very rapidly when foam is in warm ambience, so that reduces the overall energy of the system (the combustion energy is removed from the burned material).

This cooling effect is all the more important when the fire has a high temperature.

Insulation effect

Foams contain a lot of air (5 to 900 times more than the foaming solution), which leads to low thermal conductivity: foam produced as thermal insulation can be used by depositing it on the equipment (more or less flammable) that has not yet caught fire.

Then, this foam will protect against thermal radiation (known to enhance the propagation of the fire).

The low thermal conductivity of the foam insulates flammable material which has not yet caught fire or has already been extinguished against thermal radiation and ignition sources.

Blanket effect

The close foam cover stops any further gas evaporation from burning materials, i.e. flammable gases from the combustible materials can no longer get into the combustion zone and cooling the burning material at the same time reduces the vapour pressure whereby outbursts of gas and thus re-ignition are avoided.

The preventive application of foam onto spilled volatile products prevents emissions harmful to environment/reduces the danger of fire.


Which foam concentrate would you choose ?

Ai GROUP selects the best foam concentrate manufacturers with the most wanted certifications (EN, UL listed, IMO, ICAO, GOST…). Indeed, with its expertise and its lab resources, Ai GROUP can help you choose the best foam concentrates you need to ensure the safety of your staff and your equipment, with in mind:

  • Maximum firefighting performance and Minimum environmental impact
  • Top level product approvals and Comprehensive warranty

Foam uses various extinguishing effects: cooling, separating, suppressing (vapours), covering and insulating (each effect alone or in conjunction with others provides quick success in extinguishing).


Fluoroprotein foams (FFFP and AR-FFFP)

Fluoroprotein foams are used since decades in situations where hydrocarbon fuels such as crude oil, gasoline and fuel oil are stored, processed or transported. They are used extensively by major oil and petrochemical companies for hydrocarbon storage tank fire protection. Other applications include process areas, road/rail loading racks, power stations, marine terminals and airports.


AFFF foams

AFFF Foams provide fast flame knockdown and extinguishing, good burnback resistance and post-fire security.


Alocohol resistant foams AR-AFFF

AR-AFFF Foams are ideally suited for use in high risk situations where hydrocarbons (such as gasoline, diesel fuel, aviation kerosene) and/or polar solvents (such as alcohols, ketones, esters and ethers) are stored, processed or transported. Typical applications are hydrocarbon storage tanks, process areas (refineries…), pharmaceutical plants warehouses, road/rail loading racks, power stations, marine terminals and offshore platforms.


High expansion foams

Superior quality high expansion foams for extinguishing and securing flammable hydrocarbon fires. Produces an extremely stable, long-lasting foam, and is formulated for use at both medium and high expansion. Effective on a wide range of class A & B fires.

High expansion foams are ideal to use to protect storage (raw materials…).

They can also be used in conjunction with fixed installations to provide protection, where it can achieve extinction of fires or suppression of toxic vapour release after chemical spillage.


Fluorine-free foams

The ideal foam for fire professionals currently prohibited from using fluorine-based foams. These foam concentrates combine excellent performance and low environmental impact.


You have a project regarding fire protection and you are looking for a supplier with great expertise of industrial high-hazards? Do not hesitate to contact us  and one of our dedicated colleagues will contact you as soon as possible after receiving your request.