“Fire!” When yelled aloud, the word, “fire,” usually evokes fear and other strong emotions in those within the range of an individual shouting this warning. The risks associated with fighting fires fueled by explosions, natural disasters, hazardous materials or weapons of mass destruction, however, have to be confronted with fortitude and understanding by those who service fires, despite the dangers. As our technology today notably affects fire service, along with individuals who work in this service, understanding characteristics of fire, and the accompanying risks increase the likelihood of successfully encaging and destroying combustions fueled by destructive fires.
According to firefighters, “Combustion is self-sustaining,” ( McKay, G. 2002). When either of three materials necessary for fire are absent, however: oxygen, fuel (substance which will burn), or heat, combustion cannot sustain and ceases. Without all three substances, oxygen, fuel and heat, fire cannot exist.
When all three substances are present in the right circumstances, combustion occurs; solids and liquid fuels release gases that burn. Fire is reborn. “Most fires grow through three stages: incipient, smoldering and free-burning.” Although sufficient oxygen and heat exist for combustion, no flame occurs in the incipient stage while the fuel’s surface experiences decomposition. At this point, no smoke, soot or any other combustion products are visible. During the smoldering stage, combustion products may be seen, perhaps as much as 10 per cent. As the fire smolders, smoke materializes. The fire ignites into flames when the free-burning
stage transpires and the fire’s flames will then generate enough heat to warm its surrounding area.
After a fire reaches the heating stage and transmits heat to its surroundings, when the surrounding environment is flammable, and if oxygen is present, new fires can break out or combust. As fire releases energy, it is said to be “exothermic (exo: gives out; thermo: heat),” ( McKay, G. 2002). Combustion, a rapid process releasing light and heat, is a chemical reaction.
A combustible material, a substance which will burn, can be solid; liquid; gas. Heat, one energy form, when intense enough, can ignite fuel. Heat is required throughout the combustion reaction as it maintains the combustion ( McKay, G. 2002). As a liquid fuel’s temperature rises, the quantity of vapor generated increases. The lowest temperature when liquid produces vapor to form a flammable mixture with air is known as the flash point. When a substance reaches its flash point and ignites, the substance then flashes and quits burning, as inadequate heat exists to sustain an ongoing supply of vapor from the fuel. The fire point is the lowest temperature at which a substance can be ignited to sustain combustion. The ignition temperature or fire point, higher than a substance’s flash point, produces a continual vapor supply to sustain combustion.
Numerous processes occur within combustion’s flames, the fiery arena where combustion reactions transpire. In combustion, a chemical chain reaction, fuel and oxygen, the reactants, little by little, begin to form fleeting material known as chain carriers. As chain carriers speedily react with additional fuel and oxygen, more and more and more chain carriers are produced. During the fire’s course of action, the chain carriers’ processes, vital for combustion,
begin slowly, but then accelerate faster and persist until the fire’s fuel is almost consumed and the fire starts to burn out.
When fires do not burn out naturally, processes used by those in fire service and others to extinguish fires include starvation, smothering, cooling, and inhibition. Starvation involves removing fuel from the fire’s combustion reaction, while smothering consists of oxygen removal. Cooling is the process of removing heat from fire. Inhibition consists of eradicating chain carriers ( McKay, G. 2002).
Today, even more than in the past, potentially life-threatening risks exist to those responsible for encaging and destroying the fire. While serving as firefighters in the United States during 2003, according to the Department of Homeland Security’s Federal Emergency Management Agency (FEMA), 110 firefighters died. One of the risks an individual who services fires can face, that occurs infrequently, involves “a boiling liquid expanding vapor explosion, commonly called a BLEVE, ” ( McKay, G. 2002). A BLEVE commonly occurs after a liquid or liquefied petroleum gas ignites and the expanding, boiling forcefully explodes. BLEVE’s may range from minor, as when vehicles’ shocks absorbers explode in fire. On the other hand, they may qualify as massive, such as the BLEVE in Mexico City that, along with demolishing houses, injured 7000 individual and killed 300, including some who were in fire service.
Other potential risks for fire-fighters include flashovers (sometimes with accompanying explosions), backdraughts or backdrafts, and fire gas ignitions. A flashover is “a heat-induced development of a compartment fire leading to sustained combustion and a fully developed fire.” A backdraught is “a ventilation-induced ignition of fire gasses following air transport (gravity
current) into an area containing fuel ‘rich’ gases and an ignition source.” A fire gas ignition is “an ignition of accumulated fire gases and pyrolyzates existing in, or transporting into, a flammable state,” ( McKay, G. 2002).
Causes of, tactical counters, and preventive actions for flashovers, backdraughts or backdrafts, and fire gas ignitions are different. So are their warning signs. Fire-fighters are advised to understand these differences, as well as, learn and be able to identify potential accompanying conditions. Even if warning signs are not evident, firefighters are trained to be prepared for the worst in every call. Fire-fighter’s actions and/or inactions can perpetuate circumstances conducive to increasing potential harmful risks. The probability of decreasing risks arising from negative actions increase, nevertheless, when fire-fighters take care: Recognizing obvious warning signs and refuse to commit themselves or crews into dangerous conditions except to save life; utilising proper door entry system; insuring accurate tactical placement of hose-lines to guard escape routes; isolating fire in areas where water cannot be applied at once.
Gary McKay, a firefighter and author, wrote about the potential risk in fire-fighting: “But as I began to learn what the job of being a firefighter is all about I also realized that it isn’t just a matter of ‘putting the wet stuff on the red stuff.’ It is a complicated, diverse and dangerous business. Teamwork is essential for survival on the fire ground and each and every firefighter has to be extremely alert at all times. If not, they will pay a price that can be devastating to them and their fire crew. And it goes beyond this. . . It is not a job for the fainthearted. The danger of
the job was tragically illustrated when over 300 firefighters in New York City perished after the World Trade Center terrorist attack. ( McKay, G. 2002).
Even though definite differences exist between naturally occurring fires and those birthed by today’s technology, such as the horror in the World Trade Center, those who work in fire service have to be strong in mind and heart. In many ways, the dissimilar fires and the ways they have to be engaged and extinguished are similar. In the same manner that natural fires can prove to be
beneficial to the environment in a less severe form, today’s technology generates risks for destructive, life-consuming fires, but alongside the potential for risk lies the definite benefits. Just as no one knew that after the first automobile was invented, vehicular accidents would net over 250,000 deaths each year, no one can anyone whether or not potential risks for fires accompanying technology will rise or fall. What is known, on the other hand, is that emphasis and adherence to understanding and acquiring technology on how to best counter fires fueled by explosions, natural disasters, hazardous materials or weapons of mass destruction can benefit those in and out of fire service. Utilizing today’s technology to counter risks associated with fighting destructive fires’ flames when they rage out of control, in the end, not only saves property and citizen’s lives, no matter the cause. This practice also saves and enhances the lives of those who serve to save, whenever the word, “Fire!” is yelled aloud.
Delmar, a division of Thomas Learning In. The Thomson Learning. 3 C Columbia Circle
Grimwood, P. FLASHOVER TERMINOLOGY www.firetactics.com/FLASHOVER-
TERMS.htm, Nov 2002.
McKay, G. (2002). Firefighters: the men and women who risk their lives to save ours.
(McKay)Allen & Unwin 83 Alexander Street Crows Nest NSW 2065 Australia. pp. viii, 165,
176 – 178.