Our fire retardant treatment
To make wood products fire retardant, Hestus uses BurnBlock®. A proven, sustainable and certified process with which wood products reach Euro fire class B (B-s1, d0).
In short, the fire retardant ensures that oxygen cannot reach the combustible material (wood), preventing the fire from developing further. No oxygen means no fire.
Due to the heat of a fire and the absence of oxygen, the outer layer of the treated wood carbonizes. This process is called pyrolysis. The carbonized shell does not produce large flames, preventing the fire from spreading further.
Step 1: The intake
When we receive the wood at our location in Arnhem it is inspected, measured and weighed. After intake the wood is stacked with laths. We do this to ensure that the fire retardant product properly reaches the wood everywhere during the process.
Would you like to know which wood species we can directly treat with fire retardancy? Then take a look at the classification table.
Step 2: The preparation
In the upper storage tank of our installation there is a mixture of water and fire retardant. The ratio of this mixture is adjusted based on the weight, the wood species and the amount of wood that goes through the process. In this way we always use the right amount of fire retardant.
Step 3: The process: impregnating
As soon as the wood is loaded into the autoclave, air is extracted from the sealed chamber. This puts the vessel under vacuum pressure. This ensures that the pores of the wood open and the agent penetrates well into the empty cells of the wood. After this the autoclave is filled with the correct ratio of water and fire retardant. To ensure that the agent penetrates deeper into the wood, the pressure in the vessel is increased in five steps. In total this entire process takes between two and four hours.
Once the wood is saturated with fire retardant, the vessel is pumped empty. We do not discard the remaining emulsion. The residue forms the basis for the correct formula of the next batch. This way we prevent waste.
Step 4: Drying and aftercare
After the process the wood is completely soaked. To ensure that the fire retardant remains in the wood and the wood does not deform, controlled drying is important. This takes place in our drying chamber, where the wood is gradually dried back over two weeks to an ideal moisture content. Finally, the wood is weighed again for quality control and prepared for processing.
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