The Effect of Retardant Concentration on Temperature Output of Fire

Researched by Kyle W.


The purpose of this experiment was to determine which amount of flame retardant stopped the burning of wood most efficiently, also to see if flame retardant even had an effect on burning.

I became interested in this idea when last summer I was watching the news and wondered why fire fighters couldnít control the forest fires, and wondered if there could be a better way to do it.

The information gained from this experiment should help fire fighters and forest managers who are trying to control wild fires.


My hypothesis was that the concentration with the most Fyrex would work the best to control the burning of wood.

I based my hypothesis on what John Randolph of the USFS said," Fyrex is the best over the counter retardant to stop/control the burning of wood. Also if you put more on, it works better."


The constants in this study were: 

  •  amount of wood
  • amount of wind
  • method of igniting the wood 
  • thermocouple to measure the temperature 
  • same testing area
  • same barbecue
  • distance thermocouple was from the fire

The manipulated variable was the amount of retardant per piece of wood. 

The responding variable was the temperature of the fire. 

To measure the responding variable I used a computer linked to a thermocouple for 500 seconds.

72  5" by 1" by 2" sticks of wood
1 barbecue
1 thermocouple
1 stopwatch
2 one lb bags of Flame retardant
600ml water
3 loaf pans
1 saw
1 butane lighter
1  axe 
1 laptop computer


1. Cut the 1inch by 2inch lumber into 5inch long pieces.
2. Split each piece of wood in half, lengthwise with an axe- you need 36 in each of the 4 groups.
3. Treat each group of wood with the retardant.
a) Pour 100 ml of tap water into a clean metal loaf pan. 
b) Measure 27 grams of Fyrex on the triple beam balance scale.
c) Pour Fyrex into pan and mix well.
d) Dip each of the 36 pieces in pan until all surfaces are coated. 
e) Place wood on open newspaper. Let dry overnight.
f) Repeat steps a-e with 54 grams of Fyrex instead of 27.
 g) Repeat steps a-e with 54 grams of Fyrex instead of 27.
 h) Do not treat the wood in the control group. 
4. Set up the fire in the barbecue. Crumple two sheets of newspaper into balls; surround them with 12 pieces of the non-treated wood.
5. Hook up the laptop, to the temperature probe. Put the probe 10cm from the center of the fire
6. Light the fire and simultaneously push the "collect" button on the computer. This will have the probe take a reading once every second for 500 seconds.
7. Once this is done scoop out the charred remains.
8. Repeat steps 4-7 two more times.
9. Repeat steps4-8 for each of the groups of retardant: 27 grams, 54 grams, 108 grams


The original purpose of this experiment was to determine which amount of flame retardant stopped the burning of wood, most efficiently.

The results of the experiment were that the control group with no retardant had a greater burning temperature than that of wood that had been treated with retardant. The more retardant on the wood the less the temperature of the fire.

View my table and graph.


My hypothesis was that the concentration with the most Fyrex would work the best to control the fire. 

The results indicate that this hypothesis should be accepted.

Because of the results of this experiment, I wonder if a greater amount of wood, like in a forest fire, would produce different results.

If I were to conduct this project again Iíd conduct more trials. I also would try different kinds of retardants to see if Fyerx really is the best.

Fire is one the humans biggest needs. Humans need fire to cook food and keep warm. Fire also is very destructive. Each year fire claims 50,000 lives and destroys millions of acres. Fire retardant works to control the flames and save valuable land and lives.


 Scientists have found evidence that fires were a major part of human life over 1.4 million years ago. Fires tightened families as they tended to the fire and protected their young. People would hit pieces of flint with steel and sparks would fly, they also rubbed pieces of wood together and it would create a lot of friction and eventually start the fire. In the hunter gatherer days they would take burning sticks from lightning fires and guard the fire with their lives. Fire soon became understood and people started to use it for cooking, melting metals and shaping weapons. In 1777, Antoine Lavoisier proved that burning is just oxygen and other substances coming together very quickly. In the mid-1800ís a reliable match was developed. 

 Combusting is the rapid coming together of fuel, heat and oxygen.  For combustion to occur the "Fire Triangle" has to be in place.  The fire triangle is fuel, heat and oxygen. If one of the three is not present then combustion canít occur. There are three types of fuel, solid such as wood, gas such as hydrogen and liquid such as oil. To ignite the fuel the temperature has to be anywhere from 500°F-900° F for wood and 36°F or above for a gas such as hydrogen.  There are different kinds of combustion. Spontaneous Combustion is when something like paint thinner is left out in the open and it suddenly bursts into flame. The type of fuel also can vary the way it combusts, a fuel like charcoal will produce a faint glow, but a fuel such as wood will have a flame. If you burn a piece of wood it wonít burn all the way. It leaves a mineral residue called ash; ash canít burn even under the hottest circumstances. Fire can produce some harmful and dangerous gases. Smoke is a mix of gases that combustion causes, most of the fuel is used to make heat but there is a little that goes to smoke and light. Carbon dioxide can also be caused by fire. This harmful gas is caused when a gas is burned but there is very little oxygen so the entire fuel cannot be burnt.

Nothing flammable can really be fire proof. You can treat a material with a flame retardant to reduce the ability to burn. Some flame retardant increases the time it takes for the material to ignite. Some cause the material to extinguish itself. Some raise the ignition temperature, and some cut off the oxygen source to the material by forming a protective layer over it. Temporary fire retardance can be obtained by soaking materials in Borax, ammonium, and phosphate. 

To try and prevent fires, firemen inspect buildings, and also teach people about fire safety. Most of the deaths caused by fires occur in private homes. By leaving the kitchen while something is cooking, not disposing of cigarettes properly, or leaving flammable substances too close to a heat source the fire increases danger. It is important to know what to do if a fire breaks out in a home. It is important to get out of your house quickly and safety. Families are supposed to have an escape plan but many do not. People also should have fire detectors in their homes. A fire detector is a device that sounds an alarm when there is smoke in the air, warning you of a fire. Chemical retardant can be put on wood, and other materials to stop or delay burning when exposed to a flame. 

Every 13.5 seconds a fire starts in a home. Every year thousands of people die and thousands more get injured, and billions of dollars of property is destroyed. Fire is useful when controlled but can also be destructive. Fire has burned down huge sections of London, Chicago, San Francisco, Tokyo, and it burns wild and destroys large areas of trees and sometimes entire forests.

Fire can be bad but it also is needed for human survival. Many humans need fire to cook food. Without heat people couldnít cook food and could suffer from food poisoning. They also need to keep warm, without heat humans would have a harder time surviving in the winter. Fire balances out positives and negatives.


Cone, Patrick. Wildfire. Minneapolis, MN. Carolrhoda Books ,INC. 1997

"Fire." Microsoft Encarta. 2001.

"Fire Control and Safety." Career Discovery. 2000.

Nguyen, Hux X. "Bromine." Microsoft Encarta. 2001. 

OíBrien, Donald M. "Fire Prevention and Control. American Encyclopedia. 1999. 

Paulsgrove, Robin. "Fire Department." World Book Encyclopedia. 1998. 

Quintiere, James G. "Fire."  World Book Encyclopedia. 1998. 

Vinson, Bradleigh.   "Fire." World Book Encyclopedia. 2002. 

I would like to thank the following people;

  •  My Dad, for helping me cut and saw some of the pieces of wood.
  • My Mom, for picking me up after the late classes and for helping with all phases of the experiment.
  • My brother, for helping cut the wood.
  • My teacher, for staying after school to help me, coming to my house to help troubleshoot with the laptop, and for loaning me the technology to make this experiment possible.
  • To my other teacher, for helping me in all ways.

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