The purpose of fire proofing of timber is to:
Fire Retardant Treatment for Timber
Timber is an inherently combustible material. When exposed to sufficient heat, it will ignite and burn. The goal of "fire proofing" or, more accurately, fire-retardant treatment, is not to make the wood completely immune to fire, which is impossible. Instead, the objective is to improve its reaction to fire, primarily by slowing down the processes of ignition and combustion.
📝 Detailed Analysis of the Options
(a), (b), and (c)
These options describe absolute or active fire-fighting effects. Fire-retardant treatments do not actively "extinguish" fire or create a force field to keep flames away. Their function is passive; they change the chemical process of how wood burns when it is exposed to fire.
(d) Make it difficult to ignite and support its own combustion
This is the correct answer. This statement accurately describes the purpose of fire-retardant treatments. The chemicals applied to the wood work in several ways:
- They increase the temperature at which the wood will ignite.
- When heated, they can release non-combustible gases that dilute the flammable gases released by the wood.
- They promote the formation of a stable char layer, which insulates the underlying wood from heat.
🔥 Fire-Retardant Chemicals for Timber
Various chemical substances are used to make timber fire-resistant. They are typically applied as a surface coating or impregnated into the wood under pressure.
| Chemical Type | Examples |
|---|---|
| Phosphates & Sulfates | Ammonium sulfate-phosphate |
| Boron Compounds | Borax, Boric Acid |
| Chlorides | Zinc Chloride, Ammonium Chloride |
| Arsenates | Sodium Arsenate |
💡 Study Tips
- Retardant, Not Proof: Remember that timber can only be made fire-retardant (slowing fire), not completely fire-proof.
- Think "Harder to Burn": The core purpose is to make the wood harder to ignite and to make it stop burning once the external flame source is removed.
- Focus on Ignition and Combustion: The key actions are delaying ignition and preventing self-sustained combustion.