we use fire in many different ways to suit our different me on we use many different kinds of fuel here we use fire to get rid of rubbish the fuels our waste materials from about the yard breaking keeps the fire under control when we use fire to cook our food gas maybe the fuel the burner knob controls the size of the flame by regulating the flow of fuel that reaches the burner we use fire to heat our homes cool maybe the fuel when we use fire to produce light kerosene or gasoline maybe the fuel turning a knob regulates the flow of fuel and controls the flame but whatever the purpose of the fire or of the kind of fuel or the method of control all fires depend upon the same principles in order to learn more about fire let's study the campfire these boys are building dry bark and twigs are good to start the fire and the boys of heap them at the center of the pil they have chosen a site in a clearing so that the campfire can spread out of control larger branches will keep the blaze going after the bark and twigs burn out now the pile of wood is ready in a few seconds there is enough heat to set fire to the larger twigs the boys want a bigger fire so they do two things first they bring more branches and place them on the burning heat also since they know that the fire will burn faster if the circulation of air increases one of the boys fans the flames the branches just added take fire quickly with the campfire burning well and with plenty of fuel to keep it going the boys stretch out to enjoy its cheery warm when we watch a fire burning we must keep in mind that we cannot see all that is actually happening what are some of these important actions for one thing gases are given from the heated pieces of wood here black dots represent these gases oxygen represented here by a white dots is part of the air surrounding the fire when oxygen joins with the wood gases heated to their kindling points burning takes place as the oxygen and the heated gases burn another gas carbon dioxide forms the black dots joined with white dots represent carbon dioxide the large black circles unburned soup particles that rises smoke all the while fresh air blowing in at the bottom of the fire supplies needed oxygen the fire burns as long as there is fuel and oxygen when this mixture is turned off the flame goes out the supply of oxygen is regulated mainly by the draft door now let's see how this affects the burning process with that draft door only partly open a moderate supply of oxygen flowed into the firebox as the coal burns carbon dioxide in smoke form as they did in the camp fire the carbon dioxide and smoke escape through the chimney we open the draft door wider to make the fire burn faster now on the largest possible draft of oxygen reaches the fuel and speeds up the burning over fire under control may be helpful to us in many ways fire handled carelessly may cause trouble this girl should have made sure the match flame was out fortunately she knows what to do pouring water on the flame does two things it cools the fuel below its kindling temperature and it shuts off the oxygen supply many accidental fires began when small children play with matches this little boy has seen his parents strike matches so when he finds them lying around he wants  let this new play thing gets too hot to hold the panda bear takes fire and the situation is beyond the child's control it's a good thing that mother is close by and can come to the rescue the rug shuts off the oxygen supply and the fire goes out some fires start from faulty wiring such as afraid a lamp co wires touch and flames leap up this hole has a fire extinguisher handy and the blind knows how to use it how does this liquid put the fire out once in the open air the liquid quickly changes into a gas this gas will not burn instead the gas builds up in layers around the burning fuel and gradually shuts off the flow of oxygen into the burning zone cut off from its oxygen supply the fire goes out we have seen that three things are necessary for fire first we need fuel second we need enough heat to raise the field which can link temperature third there must be a supply of oxygen without oxygen there could be no fire even though we have plenty of fuel and enough heat to raise the fuel to it's killing point we have seen examples of controlled fire as we use it to burn trash to cook our food to heat our homes and to furnish light we have seen three ways of putting out accidental fires first by cooling the fuel below its kindling damper to your second by shutting off its oxygen supply using mechanical means and third by the use of the chemical as long as we keep fire under control it serves us well