Fire retardant wood is in demand by architects and builders for use in, for example, public buildings and the facades of apartment buildings, where untreated wood can't be used due to current Swedish building regulations, BBR. One way is to use fire retardant treated wood, but most traditional fire retardant do not meet the requirements for durability when used outdoor. The issue was raised at the Nordic level as a result of multiple accident investigations. Refer to the New Classes section.The major area of use is internal walls and roofing materials.
Keep in mind
It is relatively easy to achieve a high fire resistance class for wood for example through impregnating it with a fire retardant. The difficulty is not to lessen or damage the quality of other aspects of the wood. Normally it takes large amounts of additives to achieve adequate fire resistance, which often affects other properties of the wood. The additives are often water-soluble and therefore has a tendency to absorb moisture or migrating at varying humidities. This can provide high moisture ratios in fire retardant treated wood and salt precipitations on the wood surface. Indoors, this is primarily an issue of aesthetics, but outdoors the fire resistance is at risk of disappearing if the fire retardant is leached out of the material. Refer to the New Classes section.
How Do Fire Retardants Work?
The flammability of wood can be altered by chemical means with so-called fire retardants and flame retardants. Properties affected are time to ignition, flame spread, heat and smoke development. Fire retardants are mainly important in the early stages of a fire and the time until flashover can for example be extended. Fire retardants don't affect a fully developed fire to the same extent. Fire retardant treated wood can become carbonized and can not be classified as completely non-combustible. A sufficiently violent fire is able to ignite flame retardant wood.
Intumescent paints can extend the time to carbonization and thus increase the fire resistance of wood structures.
How Do You Use Fire Retardants?
Fire retardants may be added by impregnation into the wood or as a protective coating. Impregnation normally give a more durable and lasting protection.
Through all of the different stages of a fire in a building or a room fire retardants have the greatest impact in the early stages, where the surface layers flame properties can be improved. Fire retardants reduces heat generation in a fire.