than solid streams, reducing run off and the effect onship stability.ConvectionConvection is the transfer of heat through themotion of circulating gases or liquids. Heat istransferred by convection through the motion of smoke,hot air, and heated gases produced by a fire.When heat is confined (as within a ship), convectedheat moves in predictable patterns. The fire produceslighter than air gases that rise toward high parts of theship. Heated air, which is lighter than cooler air, alsorises. As these heated combustion products rise, cool airtakes their place; the cool air is heated, in turn, and thenrises to the highest point it can reach.Hot smoke originating at a fire on a low deck willtravel horizontally along passageways, and then upwardby way of ladder and hatch openings, heatingflammable materials in its path. To prevent fire spread,release the heat, smoke, and gases to the atmosphere.However, the structural design of a ship makes itdifficult to rapidly cut openings through decks,bulkheads, or the ship’s hull for ventilation. It isimperative that the fire be confined to the smallestpossible area. Doors and hatchways should be keptclosed when they are not in use. If a fire is discovered,attempts should be made to close off all openings to thefire area until firefighting personnel and equipment canbe brought into position to fight the fire.RadiationHeat radiation is the transfer of heat from a sourceacross an intervening space; no material substance isinvolved. The heat travels outward from the fire in thesame manner as light; that is, in straight lines. When itcontacts a body, it’s absorbed, reflected, or transmitted.Absorbed heat increases the temperature of theabsorbing body. For example, radiant heat that isabsorbed by an overhead will increase the temperatureof that overhead, perhaps enough to ignite its paint.Heat radiates in all directions unless it’s blocked.Radiant heat extends fire by heating combustiblesubstances in its path, causing them to produce vapors,then igniting the vapor.Within a ship, radiant heat raises the temperature ofcombustible materials near the fire and, depending onthe ship’s design, at quite some distance from the fire.Ship fires can spread as a result of radiating bulkheadsand decks. Intense radiated heat can make an approachto the fire extremely difficult. For this reason, protectiveclothing should be worn by firefighters.REVIEW 6 QUESTIONSQ1. Fire prevention is the responsibility of—Q2. List the three components that make up a fire.a.b.c.Q3. What process is involved in most cases ofspontaneous combustion?Q4. List the three methods of heat transfer.a.b.c.CLASSES OF FIRELearning Objective: When you finish this chapter, youwill be able to—Recognize the four classifications of fire andidentify the means used to extinguish them.Fires are divided into four classifications, eachindicating the type of material burning. By knowing the12-21Student Notes:
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