Direct and indirect applications of an AFFF or AR foam concentrate on class B fires

Applications directes ou indirectes de la mousse

Extinguishing a fire requires a suitable foam concentrate, and a controlled application.

There are 2 application modes, recognised by the European (EN1568) and international (ISO7203) standards.

 

 

 

Direct application

Lapplication directe

This is the direct spraying of the foam into the heart of the liquid. 
The fire fighting teams use a hose or a monitor in the "solid jet" position. This makes it possible for them to fight the origin of the fire from a distance and thus be less exposed to intense heat.
Static installations are concerned in the case of long distance static monitors, or classic headed sprinklers. The jet of spray strikes the liquid directly.
This type of spray can only be applied to class B fires of the hydrocarbon type (water-immsicible liquids), using AFFF foam concentrates (Aqueous Film Forming Foam).

 

Application directe

Application directe 2

 

 

 

 

 

 

 

 

 

 

Indirect application

Application indirecte-Schéma1

It is imperative for all polar solvent liquid fires (miscible with water).
The foam is sprayed onto a vertical surface and then runs onto the burning liquid to spread evenly on its surface without contaminating it. The foaming agent therefore strikes a surface before coming into contact with the polar product. This is the case for most fire brigade interventions and for mobile resource operating tactics.

The sprayed foam can also be applied directly onto the liquid but using Medium or High expansion. This is the case for almost all static installations (crown with ME foam box on a holding tank, HE flooding, foam head sprinkler...).
This process is mandatory so that the foam is not directly absorbed by the polar solvent. 
This method of application also allows to extinguish hydrocarbon type fires (water-immiscible liquid). 

 Application indirecte

 Application indirecte 2Application indirecte 1

 

 

 

 

 

 

 

 

There are thus 2 actions have the same extinguishing effectiveness: 

  •  Chemical action with direct application

Action chimique en application directe AFFF ENG

 

The foam generated by an AFFF foam concentrate has the property of quickly draining thus allowing the quick formation of a thin fluorine compound film at the surface of the hydrocarbon.

This heat resistant film creates a barrier that prevents the hydrocarbon vapours from igniting. 

 

 

 

 

 

 

  •  Mechanical action with indirect application 

Action mécanique en application indirect AR ENG

 

Through the accumulation of foam, a mattress forms to isolate the burning liquid.

This heat resistant thickness of foam creates a barrier that prevents the solvent vapours from igniting.

 

 

 

 

 

 

 Triangle du feu barrée EN

 

In all cases the foam concentrate makes it possible to break "the fire triangle" by isolating from the air and a cooling action of the fire's environment.

ECOPOL for example, the 1st fluorine free foam concentrate in the world, is AR and therefore perfectly effective on all class B fires. 

 

 

 

Foam action

Foam action

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Low, Medium and High Expansion

Low, Medium and High Expansion

Expansion is the ratio between the Foam Volume obtained and the Volume of Foaming Solution used to produce it. For example: 100 litres of water + foam concentrate pre-mix give 1000 litres of foam. ...

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