# Temperature vs moisture content to sustain a fire in a given material?

• mathlol
In summary, the temperature required to start burning wood is the same regardless of the moisture content. However, the heat available to burn the wood at different moisture contents is dependent on the other variables listed.
mathlol
So I've been trying to start a fire in which was successful for 10 minutes then died down due to high moisture in the leaves and branches. Which made me think of this phenomenon.

is there a graph relationship to burning an organic, non-metal material that is well defined in relation to the moisture amount? And are there better terms to describe this? I imagine the water content in wood is too general and the temperature would vary with different woods.

However, is there documented data on what temperature would be needed to burn carbon and water mixture?
I'm thinking of the x-axis having the temperature and on the y-axis a ratio of carbon to water starting at 100:0 and ending to 0:100 in which there are 100 moles of carbon to zero moles of water and ending in 0 moles of carbon to 100 moles of water. This graph could be repeated with other useful common elements or extrapolated out to other compounds to predict what temperature is needed to make wet, soggy wood burn.

x= temperature
y= material:water content

Well, wood is a lot more than carbon. You'd have to factor in the materials made using the carbon - mostly cellulose.

Chestermiller
It is complex because time and thermal environment are important.

The energy released by burning must be sufficient to vaporise all the water that is present in the material. That requires material be steadily fed into an oven to maintain the process.

The temperature needed to start wood burning is the same regardless of moisture content. The heat needed to get that temperature depends on the moisture because the water must be driven off before the wood can get hot enough to burn.

There are other variables when burning wood.

Amount of air. Too much air cools it off. Not enough air prevents it from getting hot enough to burn properly.

Heat loss. Heat loss is from radiation and conduction. Surrounding the fire with a cold surface will get different results than a hot surface.

Proximity. The distance from a burning piece to the nearest non-burning piece. If too far, not enough heat will radiate/conduct to start the adjacent piece burning.

Size. The size of non-burning pieces affects how readily they start to burn. In a cloud of dust sized dry particles, adjacent particles can catch fire which spreads to the next adjacent particles to cause a dust explosion. The opposite extreme is mass timber construction, where heavy wood structural timbers burn slow enough that the structure meets building codes for fire resistance.

The following, from Wood Combustion Principles, Processes, and Economics, by Tillman, Rossi, and Kitto, shows a theoretical calculation for the amount of heat available from wood at different moisture contents.

This book is from 1981. It is written for technical people that want to know the math and chemistry of wood combustion. There may be newer and/or better books on the subject today.

Another excellent resource, from 1976, is The Woodburners Encyclopedia. This book is for people that want less math and chemistry. It is out of print, but used copies are available. This figure is from The Woodburners Encyclopedia:

mathlol
Er yes. What jrmichler said.
Did I not cover that in post 2?

Baluncore

## 1. What is the relationship between temperature and moisture content in sustaining a fire?

The relationship between temperature and moisture content in sustaining a fire is an inverse one. As the temperature of a material increases, the moisture content decreases, making it easier for the material to ignite and sustain a fire.

## 2. How does moisture content affect the flammability of a material?

Moisture content plays a crucial role in determining the flammability of a material. A higher moisture content in a material makes it less likely to ignite and sustain a fire, while a lower moisture content increases the material's flammability.

## 3. Is there a specific moisture content threshold that can sustain a fire?

There is no specific moisture content threshold that can sustain a fire in a material. The flammability of a material depends on various factors such as the type of material, its composition, and the surrounding temperature.

## 4. Can temperature alone sustain a fire in a material?

No, temperature alone cannot sustain a fire in a material. While high temperatures can increase the likelihood of a material catching fire, the presence of fuel (such as dry or combustible materials) and oxygen are also necessary for a fire to sustain.

## 5. How does the moisture content of a material affect the spread of a fire?

The moisture content of a material can significantly impact the spread of a fire. A higher moisture content can slow down the spread of a fire, while a lower moisture content can increase its speed and intensity. This is because moisture acts as a natural fire retardant, making it harder for the fire to spread to other materials.

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