Home >> Science & Nature >> Nature

Types of Wood Burning Speeds

According to the USDA Forest Products Laboratory, wood does not actually burn but undergoes thermal degradation as it heats up, giving rise to flammable gases that "burn" when they contact a source of ignition." Wood actually combusts. The speed at which wood burns depends on the type, hardness, moisture content and chemical components of the tree where the wood originated.

Temperatures
- The reason wood or cellulose combusts is based upon its thermal decomposition when exposed to heat. This is called "pyrolysis." According to KTH Biotechnology, "combustion takes place as a reaction between oxygen and the gases released." Combustion is dependent on conditions present in the piece of wood. These include oxygen concentration, moisture, temperature and hardness of the wood. The average temperature wood starts to burn is 662 degrees Fahrenheit. Spontaneous combustion requires a temperature over 1100 degrees.
Fire Performance and Ignitability
- A freshly cut tree will contain a lot of water in the pores of its wood. It will be very heavy in weight. This is known as a "green" piece of wood. It will not burn very well unless exposed to extremely high temperatures, so its burning speed is very slow. Wood that has been allowed to dry for a few months, which is known as "seasoned wood," will have less water. Seasoned wood is lighter and will burn faster. The thicker the wood, the more time it takes to combust. Another factor is the amount of oil inside the wood. For example, eucalyptus trees burn very fast because they store oils inside them that burn rapidly. Fruit trees such as apple, cherry, and sugar maple contain few oils and burn slower. Softwood trees such as spruce, cedar, pines and poplar burn at faster rates than hardwoods such as ash, birch, chestnut and white oak.
Heat Release and Fire Spread
- Combustion and the heat that is released is the primary driving force of any fire. The more heat released, the faster the fire will spread. Factors that influence speed are the internal structural chemicals as well as external forces such as air temperature. The most important external factor is oxygen. According to KTH Biotechnology, "when wood burns, flames spread on its surface. Flame spread can be regarded as a sequence of ignition." Flame spread is also dependent on the same factors as heat release.
Charring and Smoke Production
- If wood chars quickly, it will take less time to burn. The slower the charring, the longer the wood burns. Smoke production affects the amount of oxygen available for wood to continue to burn. The higher the concentration of oxygen, the faster the wood will burn. The main byproduct of combustion is water vapor and carbon dioxide. Carbon dioxide is not only toxic to living creatures, it slows wood burning speed.

Nature