FIREFIGHTING

                                                  How does fire combust? 
                                                  David seeks an answer to this
                                                  burning question.

Contents

Insights & Connections
Vocabulary
Resources
Main Activity
Try This

INSIGHTS

Would you know what to do if a fire suddenly broke out in your home? You need to understand how fire burns, how heat energy is transferred in a fire, and how to protect yourself and others from it.

Imagine a fire triangle--one side is oxygen, one side is fuel, and one side is energy. Fire needs a source of oxygen (air, ozone, etc.) which chemically combines with fuel at a high enough temperature to maintain the fire's combustion process. If one of these three factors is missing, fire cannot exist. Fire fighters extinguish fires by removing one or more of the sides of the triangle.

Burning releases chemical energy, resulting in increased molecular motion and emission of electromagnetic waves. This increased molecular motion is detected as a rise in temperature. The energy is removed as heat by conduction, convection, and radiation. To occur, chemical reactions like burning often require a high molecular agitation--that is, a high temperature.

Conduction is the transport of heat through solids by direct contact. This transfer goes from molecule to molecule down the chain, like a row of dominos. You feel the effect of conduction whenever you touch a hot object.

Convection is the transfer of heat in fluids. The process begins by heating a fluid. As the fluid warms, it becomes less dense and rises. Colder, denser fluid then sinks down and takes the place of the warmer fluid, creating a convection cell.

Radiation is the transfer of energy through empty space or transparent materials. The energy travels in waves from the source, such as the energy that travels from the sun to Earth or the heat you feel coming from a stove. Radiation causes the temperature of materials around a fire to rise. If the temperature increases, the material may reach its ignition temperature and burst into flames, adding more fuel to the fire.

Almost 70% of fatal house fires occur at night. Smoke is the most frequent cause of death, since it displaces the oxygen we breath and fills the air with poisonous toxins. After only a few seconds in a smoke-filled room, you can become disorientated and experience distorted judgment.

You should know what to do in the event of a fire. Plan escape routes from your apartment or home and practice using them. Install smoke alarms and maintain them by cleaning and testing them monthly. Learn fire prevention and safety procedures so you know what to do if a fire breaks out.

CONNECTIONS

1. How do fire fighters extinguish different kinds of fires, such as chemical, electrical, and wood?
2. What do fire fighters try to eliminate when they fight fires?
3. How do you use the three forms of energy transfer in your daily lives?
4. What can you do to make your home safer from fire?

• combustion a chemical, physical, oxidation-reduction reaction that causes light and heat to evolve
• convection cell a circulatory flow of energy set in motion by unequal heating of a fluid
• flame retardant material that has been treated chemically to reduce its ability to ignite and spread the flame
• fire triangle three factors that make up a fire--fuel, oxygen, and energy (high temperature)
• oxygen found in air and the sole component of ozone, this gas is needed for fuel to burn at a high temperature
• temperature a measure of the average kinetic energy of molecules

Resources

• O'Donnell, J. ( 1980) Fire: Its many faces and moods. Englewood Cliffs, NJ: Silver Burdett.
• Reuter, M. (1977) Careers in a fire department. Austin, TX: Raintree/Steck Vaughn.
• Smith, B. (1981) A day in the life of a firefighter. Mahwah, NJ: Troll Associates.

Additional sources of information

• Fire Protection Through Films PO Box 11 Newton Highlands, MA 02161
• National Fire Protection Association Public Education Batterymarch Park Quincy, MA 02269 (607) 770-3000 (books on safety education)
• United States Fire Administration Office of Planning and Education Federal Emergency Management Agency Washington, DC 20472

Community resources

• Local fire department

Main Activity

The greatest threat to individuals in a fire is the smoke and toxic fumes generated from burning materials within a structure. Smoke quickly and easily moves upward through passages and openings, such as stairs and heating ducts. To understand why smoke rises so quickly, you must first understand the heat transfer process known as convection.

Materials

• incense stick
• matches
• a tall, 1-quart, large-mouth canning jar or mayonnaise or spaghetti
• sauce jar with screw-top cap three small blocks of wood or other
• suitable replacements cup of sand

1. Form into a group of four and gather your materials.
2. Arrange the wood on a flat stable surface so that a triangle forms in the center of the three pieces. Allow a slight opening at one corner of the triangle.
3. Remove the cap from the jar and place the jar upside down on the wood, making sure air can flow into it.
4. Practice placing the unlit incense stick through the opening between the wood blocks. Hold it under the mouth of the jar. 5. Have your instructor light the incense stick. Place the lit incense under the middle of the jar's opening.
5. Allow the incense to burn under the jar for two minutes. Observe how the smoke behaves.
6. Next, screw the cap on the jar and place the lit end of the incense in the cup of sand.
7. Draw a diagram of the convection cell.

Questions

1. What causes the smoke to move around in the jar?
2. Explain why the smoke moved upward as the incense burned.
3. Explain how this model is similar to smoke in a fire.
4. What happened when the smoke reached the top of the jar?
5. If you want to avoid smoke, where should you go? Explain why.

Demonstrate what sets off a smoke detector and how it operates. Discuss where smoke detectors should be placed and how they should be tested to make sure they work.

Draw a floor plan of your house or apartment. Ask your parents to help you locate and diagram escape routes in case of fire, and then practice using them. Locate areas of potential danger and the best locations for smoke alarms. Complete the fire safety checklist available from your local fire department.

Every year, fire destroys many acres of forests. Exactly how big is an acre? Calculate how many times your classroom would fit in an acre. Contact your local park authority for the number of acres of forests destroyed by fire in the United States last year. With your school as the center point, shade in the same number of acres on a map of your state.

As an ongoing activity, watch for newspaper stories about local fires. Discuss causes of each fire, whether smoke alarms were present and operational, whether injuries or deaths resulted, and steps that might have prevented the fire or casualties.

Research and discuss the major causes of fire. Divide into groups and brainstorm ways to reduce the danger or risk of fire.

Newton's Apple is a production of KTCA Twin Cities Public Television.
Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.