Essentials Ch 5 Flashcards
Combustion:
A chemical process of oxidation that occurs at a rate fast enough to produce he and and usually light (glow or flame)
NFPA 921
Pg 208
Fire
Rapid oxidation process, which is a chemical reaction resulting in the evolution of light and heat
NFPA 921
Pg 208
Oxidizer:
Any material that readily yields oxygen or other oxidizing gas, or that readily reacts to promot or initiate combustion of combustible materials
NFPA 400
Pg 208
Heat:
From of energy characterized by vibration of molecules and capable of initiating and supporting chemical changes and changes of state.
Pg 208
All fires involve a _________ chemical reaction between some type of ___ and an _______, most commonly oxygen in the air.
Heat-producing, fuel, oxidizer
Pg 208
Physical science is the study of _____ and _____ and includes chemistry and physics.
Matter / energy
Pg 208
Matter:
Anything that occupies space and mass.
Pg 208
Chemical reaction is when a substance:
Changes from one type of matter onto another, uch as two or more substances combining to from compounds.
Energy is the _____ to ____ work.
Capacity / perform
The forms of energy are classified as either ____ or _____
Potential - store energy possessed by an object that can be released
Kinetic - the energy possessed by a body because of its motion
Pg 209
What are some types of energy?
Chemical Thermal Mechanical Electrical Light Nuclear Sound Pg 209
In terms of fire behavior, the potential chemical energy of a fuel is converted to:
Thermal energy and released as heat
Pg 209
How many joules are required to raise the temp of one gram of water one degree Celsius?
4.2 joules
Pg 210
The British thermal unit refers to the amount of heat required to raise the temperature of ____ of water ____.
1 pound of water 1 degree F; 1055 Joules = 1 Btu
Pg 209
Reactions the ‘emit’ energy are:
Exothermic reactions
Reactions that absorb energy:
Are endothermic reactions (converting water from liquid to steam)
Pyrolysis:
The chemical decomposition of a solid material by heating (often preceding combustion)
Pg 210
Ignition
The process of initiating self contained combustion
Pg 210
There are two forms of ignition:
Piloted Ignition: moment when a mixture of fuel and oxygen encounters an external heat (ignition) source with sufficient heat or thermal energy to start combustion process
Auto ignition- initiation of combustion by heat but without a spark or flame
Pg 212
Fire models:
Fire Triangle - Oxygen, heat, fuel
Fire Tetrahedron - oxidizing agent, heat, Reducing agent (fuel) and chemical reaction
Pg 212
Materials that absorb heat but do not participate actively in the combustion process are:
Passive agents (i.e. Gypsum board and green vegetation)
Smoke is an aerosol comprised of:
Gases, vapor, and solid particulates
Pg 215
Smoke is the product of:
Incomplete combustion
The most common product of incomplete combustion:
CO - toxic and flammable product, acts as a chemical asphyxiant binding with hemoglobin in the blood
Hydrogen Cyanide (HCN)
Colorless, toxic of products containing nitrogen, chemical asphyxiant
CO2 is a product of complete combustion of ________ materials. Displaces _______ and acts as a ________ _______.
Organic, oxygen, respiratory stimulant.
Common products of Combustion:
CO
Formaldehyde (colorless, pungent odor irritating to the nose)
Hydrogen Cyanide (colorless, asphyxiant)
Nitrogen Dioxide (Reddish-brown gas)
Particulates
Sulfur Dioxide (colorless gas with a choking ordor
Smoke that is thick, black and pressure can emit from a structure at a high rate. This is indicative of a potentially:
Under-ventilated structure or a ventilation-controlled fire.
Pg 207
T / F Flame is a product of combustion?
True
Pg 216
Thermal Energy
The kinetic energy associated with the random mentions of the molecules of a material or object; often interchangeably with the terms heat and heat energy (measured in joules or Btu)
Pg 216
______ is the _______ element of both the fire triangle and the fire tetrahedron. Heat is kinetic energy transferred from a __________ substance to a _________ substance.
Heat / kinetic / high-temperature / low-temperature
Pg 216
Temperature systems Fahrenheit and Celsius
Conversion - C =F-32/1.8 F = C X 1.8 + 32 Boiling point - 100ºC or 212 ºF Room Temperature 20ºC or 68 ºF Freezing point 0ºC or 32ºF. All these for water Pg 217
Measure of heat?
Measurement of the ________ ______ in the particles of a sample _______ is specifically heat.
Temperature / average kinetic energy / matter
Pg 217
Sources of thermal energy:
Chemical, mechanical, electrical, light, nuclear and sound
Pg 217
What are the common sources of heat that result in the ignition of a fuel?
Chemical, electrical and mechanical
Pg 217
What is the Most common source if heat in combustion reactions?
Chemical energy…the oxidation process almost always result in the production of thermal energy
Pg 217
What is a form of oxidation where a chemical reaction that increases the temperature of a material without the addition of external heat called?
Self-heating
Pg 217
What is it called when the material is heated to its autoignition temperature?
Spontaneous ignition
Common materials to spontaneous ignite: charcoal, linseed oil-soaked rags and straw/manure
Pg 218
List ways electrical energy can generate temperatures high enough to ignite any combustible material:
Resistance heating (incandescent lamps, ranges, ovens portable heaters)
Overcurren/overload (current flowing that exceeds limits)
Arcing (when a conductor is separated, high voltage, static electricity, lightning
Sparking (the spatter of a luminous electric discharge)
Pg 219
Mechanical energy is generated by ______ or _______.
Friction or compression (compression is generated when a gas is compressed - Diesel engine, SCBA cylinders recently filled will be warm as air is compressed)
Pg 219
The _____ of ____ from one point or object to another is basic to the study of _____ _____.
Transfer of heat / fire behavior
Pg 219
T / F Heat is transferred from warmer objects to cooler objects.
True
Pg 219
T / F Objects at the same temperature cannot transfer heat.
True
For any given substance, the ______ the temperature differences between the bodies, the _______ the transfer rate.
Greater/greater
Pg 219
Transfer of thermal energy is described as ____ _____ (energy transfer over time per unit of surface area) and is typically measured in kilowatts per meter squared. Three mechanisms of heat transfer is:
Heat flux / conduction, convention and radiation.
Pg 219
Heat transfers between solid objects is called:
Conduction
Pg 220
Heat transfer due to conduction is dependent upon three factors:
Area being heated
Temp difference between the heat source and material being heated
Thermal conductivity of the heated material
Pg 220
Heat transfer of thermal energy by the circulation or movement of a fluid, liquid or gas is called:
Convention
Pg 221
When convection occurs the movement generally will be _______ because smoke and fire gases are heated and _______.
Upward / buoyant
Pg 221
What makes convection currents move laterally?
The result of differences in pressure; moving from high pressure areas to low pressure areas
Pg 221
Heat transfer by way of electromagnetic energy is:
Radiation (light waves, radio waves X-rays without an intervening medium)
Pg 222
Some factors influence radian heat transfer such as:
Nature of the exposed surfaces (dark absorb greater heat, smooth surfaces reflect more heat)
Distance between the heat source and exposed surfaces
Temperature difference between the heat source and exposed surfaces - as the heat increases the radiant energy increases by a factor of FOUR.
Pg 223
The fuel that is being oxidized or burning during combustion is known as:
The reducing agent.
Pg 223
Heat of Combustion
Heat Release Rate
Heat of Combustion - total amount of thermal energy (heat) that could be generated by the combustion (oxidation) reaction if a fuel were completely burned (measured in Btus)
Heat Release Rate (HRR) - total amount of heat released per unit time (measured in kilowatts kW and megawatts of output)
Pg 223
In terms of fire behavior, ______ is described as the HRR during _______.
Power / combustion
Pg 224
For flaming combustion to occur:
Fuels must be in the gaseous state
Pg 225
What gaseous fuels can be the most dangerous of all fuel types and why?
Methane, hydrogen, and acetylene
They are already in the physical state required for ignition
Pg 225
The density of gases on relation to air is:
Vapor density; vapor density less than 1 is lighter than air, greater than 1 is heavier than air
Pg 226
T / F Gases that expand are more dense when heated.
False - expand are less dense when heated, when cooled they contract and become more dense.
Pg 226
Density of liquids compared with the density of water is:
Specific Gravity - mass or weight of a substance compared to the mass of an equal volume of water at a given temp. Water has a specific gravity of 1. (Gasoline is lighter and floats)
Pg 226
Flash point less 100 ºF and a vapor pressure not exceeding 40 psi is:
Flammable Liquids
Pg 226
When a liquid reaches the pressure to evaporate is called the liquid’s:
Vapor pressure - high vapor pressure presents a special hazard to FFs.
Pg 226
Minimum temp at which a liquid gives off enough vapors to form an ignitable mixture with air near the liquid’s surface.
Flash point - liquid gives off enough to vapors to ignit, but not sustain combustion
Pg 227
Them at which a liquid fuel produces sufficient vapors to support and sustain the combustion reaction.
Fire point - usually a few degrees above flash point
Pg 227
Solubility describes the extent a substance with mix with _______. Materials that are _______ in water will mix in any proportion. Liquids such as _______ _____ are lighter than water and do not mix with water. ______ ______ will mix readily with water.
Water / miscible / Hydrocarbon fuels (gasoline, diesel and oils) / Polar Solvents (alcohols, methanol, ethanol)
Pg 227
Do liquids that are less dense than water extinguish well with water?
No, should be extinguished using foam or chemical agent.
Pg 227
Liquids having a flash point at or above 100 ºF and below 200 ºF is a
Combustible Liquid
Pg 228
Pyrolysis occurs faster in wood products or plastics and why?
Plastics due to not having moisture content
Pg 228
Will a solid substance ignite easier with a low or high surface to mass ratio?
The higher the surface to mass ratio, the higher the ability to ignite will occur. (Log-low ratio vs saw dust- high ratio)
Pg 229
At normal temp (68 ºF) materials can ignite and burn at O2 concentrations as low as _____.
14% (normal air O2 concentration is 21%)
Pg 231
At what concentration of oxygen is considered enriched?
23.5 percent where 19.5 percent is being oxygen deficient
Pg 231
Common oxidizers:
Calcium Hypochlorite - granular solid (chlorine for swimming pools)
Chlorine - gas (water purification)
Ammonium Nitrate - granular solid (fertilizer)
Hydrogen Peroxide -liquid (industrial bleaching, pulp and paper)
Methyl Ehtyl Ketone Peroxide (catalyst in plastics manufacturing)
Pg 231
What gaseous fuels can be the most dangerous of all fuel types and why?
Methane, hydrogen, and acetylene
They are already in the physical state required for ignition
Pg 225
The density of gases on relation to air is:
Vapor density; vapor density less than 1 is lighter than air, greater than 1 is heavier than air
Pg 226
T / F Gases that expand are more dense when heated.
False - expand are less dense when heated, when cooled they contract and become more dense.
Pg 226
Density of liquids compared with the density of water is:
Specific Gravity - mass or weight of a substance compared to the mass of an equal volume of water at a given temp. Water has a specific gravity of 1. (Gasoline is lighter and floats)
Pg 226
Flash point less 100 ºF and a vapor pressure not exceeding 40 psi is:
Flammable Liquids
Pg 226
When a liquid reaches the pressure to evaporate is called the liquid’s:
Vapor pressure - high vapor pressure presents a special hazard to FFs.
Pg 226
Minimum temp at which a liquid gives off enough vapors to form an ignitable mixture with air near the liquid’s surface.
Flash point - liquid gives off enough to vapors to ignit, but not sustain combustion
Pg 227
Them at which a liquid fuel produces sufficient vapors to support and sustain the combustion reaction.
Fire point - usually a few degrees above flash point
Pg 227
Solubility describes the extent a substance with mix with _______. Materials that are _______ in water will mix in any proportion. Liquids such as _______ _____ are lighter than water and do not mix with water. ______ ______ will mix readily with water.
Water / miscible / Hydrocarbon fuels (gasoline, diesel and oils) / Polar Solvents (alcohols, methanol, ethanol)
Pg 227
Do liquids that are less dense than water extinguish well with water?
No, should be extinguished using foam or chemical agent.
Pg 227
Liquids having a flash point at or above 100 ºF and below 200 ºF is a
Combustible Liquid
Pg 228
Pyrolysis occurs faster in wood products or plastics and why?
Plastics due to not having moisture content
Pg 228
Will a solid substance ignite easier with a low or high surface to mass ratio?
The higher the surface to mass ratio, the higher the ability to ignite will occur. (Log-low ratio vs saw dust- high ratio)
Pg 229
At normal temp (68 ºF) materials can ignite and burn at O2 concentrations as low as _____.
14% (normal air O2 concentration is 21%)
Pg 231
At what concentration of oxygen is considered enriched?
23.5 percent where 19.5 percent is being oxygen deficient
Pg 231
Common oxidizers:
Calcium Hypochlorite - granular solid (chlorine for swimming pools)
Chlorine - gas (water purification)
Ammonium Nitrate - granular solid (fertilizer)
Hydrogen Peroxide -liquid (industrial bleaching, pulp and paper)
Methyl Ehtyl Ketone Peroxide (catalyst in plastics manufacturing)
Pg 231
The range between the upper and lower flammable limit in which a substance can be ignited -
Flammable (explosive) range
Pg 232
The range in which the gas or vapor is too rich to burn -
Upper flammable limit (UFL)
Pg 232
The range where the the flammable gas or vapor is below the this limit is considered: (too lean)
Lower flammable limit (LFL)
What are electrically charged and highly reactive parts of molecules?
Free Radicals and are highly reactive
Pg 233
Stages of fire development:
Incipient Growth Fully developed Decay Pg 234
At a fire scene, the stages of fire development are a guid for what ______ occurs during the fire but are not a pattern of _____ occur every time.
Could / will
Pg 234
In a compartment fire, what is one of the most fundamental Class A fuel characteristics influencing fire development?
Surface to mass ratio
Pg 235
How can ventilation be influenced in a compartment?
Size, number denotes locations of openings as well as the velocity of the air being exchanged (ventilation occurs naturally during fire conditions - this is not to be confused with tactical ventilation)
Pg 238
List the differences between fuel-controlled vs ventilation-controlled fires
Fuel-controlled is sufficient oxygen is available and the fuel controls the fire development
Ventilation-controlled is when the available air supply begins to limit fire development and the available air supply will determine the speed of fire development.
Pg 239
High humidity and cold temperatures will slow or speed up the natural movement of smoke?
Slow
Pg 240
Ceiling jet is referring also to:
Mushroom effect - collection of hot gasses at the ceiling spreading laterally
Pg 242
Heat stratification and thermal balance refers to:
Thermal Layering - tendency of gases to form into layers according to temperature
Pg 244
What is the level of an opening where hot gases and cooler air is exchanging called?
Neutral Plane - hot gases are leaving the topside and cooler air is incoming below - the pressure is neutral (hot gases higher than cooler air lower)
Pg 244
When all the combustibles in a compartment are burning; the fire is considered in what stage?
Fully developed
Pg 246
What terms are used for rapid fire development?
Flashover
Backdraft
Smoke explosion
Pg 247
When conditions turn from two layer environment (hot on top and cooler on bottom) to a single layer environment (hot top to bottom), this is considered what type of conditions for rapid fire development?
Flash over conditions
Pg 247
Four common elements of flashover:
Transition in fire development- growth to fully developed
Rapidity - flashover happens rapidly to spread complete fire involvement within the compartment
Compartment - must be an enclosed space such as single room
Ignition of ALL exposed surfaces - all combustible surfaces in an enclosed space become ignited
Pg 247
Two interrelated factors determine whether a fire within a compartment will progress to flashover:
Sufficient fuel and heat release rate sufficient to support flashover
Ventilation - fire must have enough oxygen to support flashover (sealed room may not)
Go 248
Usually the temperature which flashover occurs is:
1110 ºF
Pg 248
One possible indicator for flashover is the condition of unburned gases on the upper layers produce flames
Also called as rollover
Pg 248
What stage will a backdraft explosion occur?
Decay stage when it may be vent-controlled.
Turbulent smoke with high velocity or with pulsing air movement are smoke indicators of what:
Flashover
Dense smoke, light colored or black becoming dense gray-yellow are indicators of:
Backdraft
Pg 249
How can firefighters influence fire behavior?
Temperature reduction Fuel removal Oxygen exclusion Chemical flame inhibition Ventilation and fire behavior Pg 250
What are the effects of water on fire?
Absorbs significant heat, but it’s greatest effect is when water is vaporized into steam. When water reaches 212ºF, it expands 1700 times
Pg 251
Control steam production by:
Use good nozzle technique
Apply the appropriate amount of water
Apply water using the most effective form of stream
Pg 251
