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Chapter

FSC239 Ch 25
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Department
Forensic Science
Course
FSC239Y5
Professor
Cahn
Semester
Winter

Description
FSC239 January 6 th Ch. 25 – pgs 507 to 524 Basic Fire and Explosion Investigation - the basic method is the systematic approach that address the following criteria o 1. recognition of the need: determine how the fire or explosion occurred o 2. definition of the problem: how can the problem be solved o 3. collection of the data: facts about the fire incident are now collected o 4. analysis of the data: all the collected and observed data is analyzed Fire - fire: the rapid oxidation process with the evolution of heat and light - 4 components necessary for fire: fuel, heat, oxygen, and uninhibited chemical chain reactions - fuel: any substance that will burn or support combustion o 3 basic states: solid, liquid, gaseous vapour  can only be volitalized and consumed in the vapour form - if oxygen in the environment is limited, it results in the production of CO o carbon monoxide asphyxiation is the primary cause of death in fires - flashpoint: the temperature at which a liquid gives off sufficient vapours to form an ignitable mixture at its surface - fire point: the temperature at which a liquid produces vapours that will sustain combustion – generally several degrees higher than the flashpoint - heat: the component necessary to increase the temperature of the fuel in the presence of oxygen and cause ignition o energy possessed by a material or substance due to molecular activity - 5 basic methods of heat production o 1. chemical: production of rapid oxidation o 2. mechanical: production of friction o 3. electrical: product of arcing, shorting, or other electrical malfunction o 4. compressed gas: molecular activity is increased – heat is generated o 5. nuclear: product or splitting of atomic particles - 3 forms of heat transfer o 1. conduction: transfer of heat through direct contact o 2. convection: transfer of heat by a circulation medium – air/water o 3. radiation: - chemical chain reaction require 2 things: o 1. oxidation reaction produces sufficient heat to maintain continued oxidation o 2. the fuel mass must be broken down into similar compounds and liberate from the mass itself - fire follows a path of least resistance - during fire’s progression, it normally transcends 4 phases o 1. incipient: may last a fraction of a second to several hours or days depending on the fuel or ignition source o 2. emergent smouldering: products of combustion become increasingly pronounced o 3. fire burning: rate and intensity of open fire increases – intensity doubles with each 18 F/10 C o 4. oxygen regulated smouldering: when the oxygen in the air is
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