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135 Cards in this Set
- Front
- Back
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What is physical science?
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the study of the physical world around us and includes the sciences of chemistry and physics
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What is matter
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anything that occupies space and has matter
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What is exothermic heat reaction?
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chemical reaction between two or more materials that changes the materials and produces heat, flames, and toxic smoke
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What is endothermic reaction?
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chemical reaction in which a substance absorbs heat energy
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What is combustion?
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an exothermic chemical retain that is a self-sustaining process of rapid oxidation of fuel that produces heat and light
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Converting water from a liquid form into a gas steam is what type of reaction?
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endothermic physical reaction
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What is non flaming combustion?
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solid feels go through oxidation at the surface of the fuel that is non flaming, also called smoldering combustion
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What is the level of oxygen found in our environment?
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21%
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The fire triangle represents a reasonable explanation of what type of combustion?
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nonflaming or smoldering combustion
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Flaming combustion is more accurately explained using what?
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the fire tetrahedron
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Another name for a fuel is what?
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reducing agent
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If the chemical reaction is inhibited in the fire tetrahedron what will be ceased and what may still exist?
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flaming combustion will cease, smoldering may continue
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What is potential energy?
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the energy possessed by an object that may be released in the future
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What is kinetic energy?
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the energy possessed by a moving object
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Heat is what type of energy?
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kinetic
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Temperature is a measurement of what?
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kinetic energy
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Energy is what?
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the capacity to perform work
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Is it possible to measure energy directly?
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no, it is possible to measure the work that it does
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What is the measure of heat energy in the International System of Units?
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joule. a joule is equal to 1newton over a distance of 1 meter
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What iIn the customary system the unit of measure for heat is what?
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British thermal unit (BTU), the amount of heat required to raise the temperature of 1lb of water 1degree F
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What is the energy component of the fire tetrahedron?
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heat
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What is boiling and freezing?
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F - 32, freezing, 212, boiling
C- 0, freezing, 100, boiling |
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What is pyrolysis?
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the chemical decomposition of a substance through the action of heat
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Pyrolysis takes place in which type of fuels?
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solid, releases ignitible vapors or gases
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Liquid fuels do not go through pyrolysis, they go through what?
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vaporization
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Autoignition temperature is what?
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the temperature which the surface must be heated for ignition and self sustained combustion to occur
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The autoignition temperature is always higher than what?
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the piloted ignition temperature
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Which is more common piloted or autoignition?
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piloted
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What are sources of heat energy?
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chemical, mechanical, electrical, light, nuclear, and sound
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What is the most common source of heat in combustion reactions?
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chemical heat energy
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When any combustible is in contact with oxygen what occurs?
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oxidation, and almost always the production of heat
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Copper will conduct heat how many more times than steel?
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7
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Steel is how many times more thermally conductive than concrete?
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nearly 40
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What can retard the transfer of heat, primarily by slowing conduction from one body to another?
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insulation materials
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Gases do not conduct heat very well why?
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because their molecules are rather far apart
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The best commercial insulators used in building construction are those made of what?
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fine particles or fibers with void spaces between them filled with a gas such as air
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What is convection?
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the transfer of heat energy from a fluid (liquid or gas) to a solid surface
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What is radiation?
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the transmission of energy as an electromagnetic wave (such as light waves, radio waves, or X-rays) without an intervening medium
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All matter radiates heat except matter at what temperature?
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below absolute 0
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Radiant heat become the dominant mode of heat transfer in a fire when?
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when the fire grown in size and can have a signifiant impact on the ignition of objects located some distance from the fire
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Radiant heat transfer is a significant factor in fire development and spread in what?
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compartments
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What factors influence radiant heat transfer?
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nature of the surfaces, distance between surfaces and the heat source, darker materials will emit and absorb heat more effectively than lighter, smooth or highly polished surfaces will reflect radiant heat more than rough
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As the temperature of the that source increases the radiant energy increases by a factor of what?
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to the fourth power
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Radiant heat travels how?
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through electromagnetic waves through space in a straight line
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What type f beast causes most exposure fires?
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radiant
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Materials that reflect radiated energy will do what to the transmission of heat?
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disrupt it
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What is a passive agent?
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a material that absorbs heat but does not participate actively in the combustion reaction
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Fuel moisture in an object is known as what?
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passive agent
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Inorganic materials do not contain what?
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carbon
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What is vapor density?
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the density of gases in relation to air, air is given 1
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What is the vapor density and ignition temp of methane (natural gas)?
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.55, 1004degrees F
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What is the vapor density and ignition temp of propane (liquefied petroleum gas)?
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1.52, 842degrees F
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What is the vapor density and ignition temp of carbon monoxide?
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.96, 1128degrees F
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What happens to gases when heated or cooled?
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heated expand and less dense, cooled contract and more dense
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Vapor density is measured at what air temp/gas temp?
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68degrees F
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Gases have mass but no what?
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definite shape or volume
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Liquids have mass and volume but no what?
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definite shape except for flat surfaces
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What is specific gravity?
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the ratio of the mass of a given volume of liquid compared with the mass of an equal volume of water at the same temp. water is specific gravity 1
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Epichlorohydrin (used in making plastics) has a specific gravity that is less or greater than 1?
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greater
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What is atmospheric pressure at sea level?
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14.7
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In order to vaporize liquids must overcome what pressure?
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atmospheric
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What is vapor pressure in liquids?
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the pressure produced or exerted by vapors released by the liquid
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What is volatility?
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the ease with which a liquid gives off vapor
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Flash point, the temperature at which a liquid gives off sufficient vapors to ignite but not sustain combustion is also known as what?
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piloted ignition
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What is commonly used to indicate the flammability hazard of liquid fuels?
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flash point
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What is the specific gravity of gasoline and its flash point and autoignition temperature?
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.8 or .72, -32degrees F, 853degrees F
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What is the specific gravity of epichlorohydrin?
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1.18
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The more the surface area exposed to atmosphere the more or less vapor is given off?
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more
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Which type of fuel mixes and does not mix with water?
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-hydrocarbon does not mix (gasoline, diesel, fuel oil)
-polar solvent mixes with water (alcohols like methanol, ethanol) |
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Solubility is what?
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the extent to which a substance will mix with water
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What are miscible materials?
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materials that are capable of being mixed in any proportion
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Diesel has what specific gravity flash point and autoignition temp?
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>1.0, 125degrees F, 410F
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Ethanol has what specific gravity flash point and autoignition temp?
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.78, 55F, 689F
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Methanol has what specific gravity flash point and autoignition temp?
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.79, 52F, 867F
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What type of plastic does not melt and change form?
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thermosetting plastics
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Pyrolysis begins at temperatures below what?
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400F
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Which temp is required for ignition of vapors being given off?
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apx 1000F, this is where free burning exists
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Surface to mass ratio increases does what?
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increases increases ignitability, or lowers the energy required for ignition
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Heat of combustion is expressed how?
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in kilojoules/gram (kJ/g)
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What is heat release rate?
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the energy released per unit of time as a given fuel burns and is usually expressed in kilowatts (kW)
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HRR is dependent on what?
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the type, quantity, and orientation of the fuel, and the characteristics of the enclosure. HRR varies over time
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What is the HRR of polyurethane sofa?
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3120
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What is the HRR of Polyurethane easy chair?
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1350-1990
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What is the HRR of polyurethane mattress?
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810-2630
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What is the HRR of a dry christmas tree?
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500-650
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What is the HRR of small pool of gasoline?
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400
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What is the HRR of cotton easy chair?
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290-370
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What is the HRR of cotton mattress?
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130-350
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What is the HRR of small wastebasket?
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4-18
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Fuel is also known as what?
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reducing agent
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What are oxidizers?
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not combustible but like oxygen they will support combustion
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At normal temperatures (70F) materials can ignite and burn at oxygen concentrations of what?
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as low as 14%
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What are some common oxidizers?
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calcium hypochlorite (granular solid, pools), chlorine (gas, water purify), ammonium nitrate (granular solid, fertilizer), hydrogen peroxide (liquid, bleaching), methyl ethyl ketone peroxide (plastics manufacturing)
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What might keep flaming combustion at considerable lower temperatures?
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high ambient temperatures
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OSHA 29 CFR 1910.134 defines atmospheres having less that what oxygen as deficient and requiring SCBA?
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19.5%
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Oxygen levels above what concentration classifies the atmosphere as oxygen enriched and presents an increased fire risk?
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23.5%
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When placed in oxygen atmosphere of what nomex ignites and burns vigorously?
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31% oxygen
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What is the flammable range of methane?
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5-15%
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What is the flammable range of propane?
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2.1-9.5%
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What is the flammable range of carbon monoxide?
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12-75%
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What is the flammable range of gasoline?
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1.4-7.4%
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What is the flammable range of diesel?
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1.3-6%
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What is the flammable range of ethanol?
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3.3-19%
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What is the flammable range of methanol?
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6-35.5%
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Complete oxidation of methane results in production of what?
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carbon dioxide and water
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What are free radicals?
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electrically charged, highly reactive parts of molecules that combine with oxygen or with the elements that form the fuel material producing intermediate combustion products (new substances) producing even more radicals an increasing the speed of the oxidation reaction
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At various points in the combustion of methane the process results in the production of what two flammable and highly toxic substances?
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carbon monoxide, formaldehyde
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What is chemical flame inhibition?
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when a halon replacement extinguishing agent interferes with the chemical reaction forming a stable product and terminates combustion reaction
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What is CO a byproduct of?
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combustion of organic materials
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How is hydrogen cyanide produced (HCN)?
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combustion of materials containing nitrogen
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HCN does what to asphyxiate?
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prevents the body from using oxygen at a cellular level. it is found significantly in polyurethane foam combustion
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CO2 displaces oxygen and because of that is a simple asphyxiant, it also does what to respirations?
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it is a respiratory stimulant, increases respiratory rate
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What makes a flame burn less luminous?
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more complete combustion
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Flame is considered a product of what?
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combustion
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What are some class d fuels?
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aluminum, magnesium, potassium, sodium, titanium, zirconium
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What is saponification?
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a phenomenon that occurs when mixtures of alkaline based chemicals and certain cooling oils come into contact resulting in the formation of a soapy film that extinguishes the fire (class K fire)
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After ignition what are the stages of a fire?
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incipient, growth, fully developed, decay
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What stage does flashover occur?
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fully developed
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What is another name for mushrooming?
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ceiling jet
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Incipient to growth can happen how fast?
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seconds
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Is two-in-two-out required in the incipient stage?
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no
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The interface of hot and cooler gas layers at an opening is referred to as what?
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neutral plane
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What is ghosting?
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as the fire moves through the growth stage, pockets of flames may be observed moving thorough the hot gas layer above the neutral plane
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Ghosting is classified as what, and may indicate what?
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a fire gas ignition, and may be an indicator of developing flashover
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What stage is flashover?
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the rapid transition between growth and fully developed fire
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Radiant heat during flashover is not survivable for longer than what?
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a few seconds even with full pep and can be faster than ff's can back away
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What is the range for flashover?
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900-1200F
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What is the autoignition of CO?
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1128F
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What is deflagration?
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explosively rapid combustion
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Is it correct that backdraft will always occur immediately or soon after making an opening into the building or involved compartment?
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no
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The a compartment fire the most fundamental fuel characteristics influencing fire development are what?
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mass and surface area
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Thermal properties of the enclosure include what?
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insulation, heat reflectivity, retention, and conductivity
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At which point does water have its most significant heat absorption?
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when it is vaporized into steam at 212F, expanding 1700:1
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What is the simplest method of removing fuel from a fire?
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allow it to burn until all fuel is consumed
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What type of fires may halon and halon replacement agents not be practical on?
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smoldering, because these are chemical inhibition agents and on smoldering fire chemical reaction is not part of the fire triangle
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