One of the most spectacular and horrifying events captured on video and seen all over the world was the collapse of the twin towers of the World Trade Centre; albeit designed and built to withstand the impact being hit by an aircraft, the resultant inferno weakened the hardened steel structures to the point that they could no longer withstand the weight of the building leading to the collapse. This is an example of how bad things could get if a fire gets out of control, more so within a building and/or encompassing it.
A fire is an event, rather than an object, occasioned when an exothermic reaction produces both heat and light. The National Fire Protection Association (NFPA) however goes further to define a fire as the chemical process of rapid oxidation that results in the evolution of various intensities of light and heat (NFPA, 2016). The process of commencement and increase of a fire involves gases in both cause and effect roles that supplement one another as a single flame increases into an inferno.
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The National Institute of Standards and Technology (NIST) has conducted extensive research on how fires start and develop from an indoors perspective and created a small film christened Flashover compilation video that shows different scenarios where fires commence and rapidly engulf and consume every combustible element in an average apartment. This includes one scenario where a dry wood and leaf Christmas tree creates a roaring inferno that burns itself and everything in the apartment room out in less than 60 seconds while another shows a fire emanating from an ordinary sofa, which could be caused by any in adventure, grows and engulfs the room in under 3 minutes.
The apartment room where the experiment occurs mirrors those inhabited by the lower social classes with floor dimension of about 30 feet by 20 feet and a ten foot high ceiling. The main theme of this video collection is to show the evolution of indoor fires from the tradition when it would take the better part of an hour for a fire to spread to the current scenario where everything is consumed even before the fire alarms sound elicit a reaction (NIST, 2010).
Commencement of a fire and its subsistence
Gases are vital for the commencement and survival of any fire as the three basic ingredients of any fire are a fuel, a certain amount of heat and an oxidizing element, commonly the oxygen found in the air. Upon commencement, the fire generates an exothermic chain reaction that ensures that the fire continues until any one of the three basic elements either runs out or is removed. For example, the physical removal of the fuel, the introduction of a cooling agent to reduce the heat or the application of any element that physically or chemically inhibits the presence of oxygen will automatically extinguish the fire (NIST, 2010).
In some uncommon scenarios however, the oxidation agent in not oxygen but perchlorate salts like ammonium perchlorate, or chlorine trifluoride (NFPA, 2016). Some weapon generated fires may also have the same element acting as both the fuel and oxidation agent a good example being nitroglycerin. Such fires are virtually impossible to extinguish and can only be allowed to flame out as and when the fuel or oxidation agent runs out (NFPA, 2016).
Another role played by gases in a fire is the facilitation of spreading of heat through convention which causes the other sources of fuel within the proximity of a fire to also ignite. Smoke, which consists mostly of fire plays this role exceptionally well especially in an apartment scenario where the smoke will hit the roof, accumulate then start spiraling downward creating an effective vehicle for transmission of heat to other fuel sources (NIST, 2010). It is clear from the foregoing that gases play a fundamental role in the commencement, spreading and subsistence of a fire and if this understanding is well harnessed, it would be easier to reduce both the occurrences of fires and the level of damage occasioned thereby.
References
NFPA (2016). All about fire . Retrieved from <http://www.nfpa.org/news-and-research/news-and-media/press-room/reporters-guide-to-fire-and-nfpa/all-about-fire/>
NIST (2010). Fire dynamics . Retrieved from <http://www.nist.gov/fire/fire_behavior.cfm/>
