How does fire spread on wood?
When wood burns, flames spread on its surface. Flame spread can be regarded as a sequence of ignitions. Therefore, flame spread is governed by the same factors as ignition. The heat released by a burning area has an effect on flame spread rate, directly by the flames and through the warming-up of the fire enclosure.
Why is fire attracted to wood?
Wood, for example, contains molecules made from bound atoms of carbon, hydrogen and oxygen (and smaller amounts of other elements). When wood gets hot enough — such as when lightning hits or a log is tossed on an already burning fire — those bonds break.
What causes a fire to spread?
A fire spreads by transferring heat energy in three ways: Radiation, Convection, and Conduction. Radiation refers to the emission of energy in rays or waves. Heat moves through space as energy waves. Most of the preheating of fuels ahead of a fire is by radiation of heat from the fire.
Is wood prone to fire?
The demand to use wood and wood-based products for applications in both residential and non-residential building construction has been increasing over recent years. However, due to the inherent flammability of such products, they often contribute to unwanted fires, resulting in numerous injuries and fatalities.
What happens to wood as it burns?
When wood is burned, oxygen and other elements in the air (mainly carbon, hydrogen and oxygen) react to form carbon dioxide that is released into the atmosphere, while the minerals turn into ashes. Thus the carbon is left to turn into charcoal.
What causes wood to spark?
When wood in a fire gets hot enough, the cellulose inside starts to turn into gas. As wood burns, the mix of expanding gases and cellulose breaking down makes the pockets of trapped steam burst open from the wood, one by one. This is why you hear the crackling and popping noises.
What are the four main ways that a fire can spread?
There are 6 ways in which a fire will commonly spread:
- Direct Contact. Initially, this is how fires normally spread until the heat builds up.
- Radiation. As a fire increases in intensity, it will give off more heat.
- Conduction.
- Convection.
- Flashover.
- Backdraught.
What makes timber fireproof?
When exposed to the heat of a fire, timber goes through a process of thermal breakdown into combustible gases. During this process, a layer of charcoal forms on the burning surface of the timber and it is this charred layer that is the key contributing factor in timber’s fire resistance.
What happens when wood is exposed to heat?
When timber is subjected to heat, it expands. This process is known as thermal expansion and can cause warping, swelling and potentially shrinkage. Wood can perform much better under heat stress than several other materials that you might consider to be hardier.
What is the basic mechanism of fire spread?
The basic mechanism of fire spread starts with the heat produced by an existing fire. The heat is transferred to unburnt combustibles nearby. This transfer can be either direct or indirect. The combustible is heated to the temperature where it can start burning.
How does the flame spread of wood vary?
The flame spread index may depend on density, thickness, chemical composition, and surface characteristics. Finishes on the wood may affect the flame spread index depending on the thickness and composition of the finish. Changes in the procedures for calculating the flame spread index have also affected the numbers.
How does the wind help a fire spread?
Oxygen always facilitates the combustion process. It allows the fire to spread and not to blow off. This is why we have been taught to cover people on fire with thick blankets to allow oxygen to die out. So with wind blowing and oxygen in there, fire is bound to spread in the direction the wind blows.
What happens to atoms in wood when it burns?
Wood, for example, contains molecules made from bound atoms of carbon, hydrogen and oxygen (and smaller amounts of other elements). When wood gets hot enough — such as when lightning hits or a log is tossed on an already burning fire — those bonds break. The process, called pyrolysis, releases atoms and energy.
How does the process of fire take place?
When metal rusts, the process happens very slowly, but when a fire burns, heat and energy is released very quickly. The rate of oxidation is especially fast with fuel sources such as paper and wood. When heat can’t release faster than it’s created, combustion occurs. This is what creates the flame and heat we call fire.
