What is AVD?



AVD

Aqueous Vermiculite Dispersion (AVD) fire extinguishing agent is a new, revolutionary technology that has key benefits over existing solutions utilising fixed and portable delivery techniques. AVD is an aqueous dispersion of chemically exfoliated Vermiculite is applied in the form as a mist. Vermiculite is the name given to a group of hydrated laminar minerals which are Aluminium-Iron-Magnesium Silicates. Raw vermiculite consists of thin, flat flakes containing microscopic layers of water.

When Vermiculite is exfoliated either thermally or chemically, the microscopic layers of water are removed and this either causes expansion (thermally exfoliated) or creates microscopic, individual platelets that are freely suspended in water (chemically exfoliated).


Due to the reactivity between a flammable metal fire and water, AVD is applied in the form of a "mist". The Vermiculite particles within the mist are deposited on the surface of the burning fuel to create a film over the top of the fire. This film instantly dries and because the high aspect ratio platelet particles overlap and bind together, they produce a non-flammable oxygen barrier between the fire and the atmosphere.

This process offers cooling to the surface of the fire and as the AVD platelets begin to build up layer upon layer of vermiculite particles on the top of the fuel source, the fire is gradually cooled and brought under control. Unlike other Class D Extinguishing Agents where the fire has to be left for long periods of time before the fire is truly under control and completely burnt out, AVD offers rapid control of the fire.

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magnesium fire stage one

When Magnesium granules are combined with moisture at elevated temperatures, a fire can begin.

magnesium fire stage two

If water is added to extinguish this, the magnesium reacts violently liberating hydrogen gas.

magnesium fire stage three

AVD Dry Mist is discharged onto the fire, the aqueous elements of AVD Dry Mist evaporate before the platelets reach the fuel.

magnesium fire stage four

A dry, oxygen barrier of AVD platelets gradually forms on top of the fuel stopping further production of flammable gases, cooling and controlling the fire.